Specifically the following critical elements must be addressed:
IV. Trade-Off Studies
A. Identify the trade-off studies that were conducted. For example, what engineering trade-offs had to be examined before a design was settled upon? Use specific examples to illustrate.
B. Evaluate the team’s decision making about the system’s technical specifications, using specific evidence to support your claims. For example, how were the systems’ major components, operations, and structures determined? Was each decision properly informed by the trade-off studies? Why or why not?
C. Evaluate the team’s decision making about the development’s project management, using specific evidence to support your claims. For example, how were potential cost and schedule overruns and performance shortfalls predicted, averted, or otherwise handled? Was each decision properly informed by the trade-off studies? Why or why not?
Guidelines for Submission: Summit a 2 page microsoft word document, double spaced, using 12-point Times New Roman font and one-inch margins.
GLOBAL POSITIONING SYSTEM
SYSTEMS ENGINEERING
CASE STUDY
4 October
2
007
Air Force Center for Systems Engineering (AFIT/SY)
Air Force Institute of Technology
29
50 Hobson Way, Wright-Patterson AFB OH
4
5433-7765
Preface
In response to Air Force Secretary James G. Roche’s charge to reinvigorate the systems
engineering profession, the Air Force Institute of Technology (AFIT) undertook a broad spec-
trum of initiatives that included creating new and innovative instructional material. The material
included case studies of past programs to teach the principles of systems engineering via “real
world” examples.
Four case studies, the first set in a planned series, were developed with the oversight of
the Subcommittee on Systems Engineering to the Air University Board of Visitors. The
Subcommittee included the following distinguished individuals:
Chairman
Dr. Alex Levis, AF/ST
Members
Tom Sheridan, Brigadier General
Dr. Daniel Stewart, AFMC/CD
Dr. George Friedman, University of Southern California
Dr. Andrew Sage, George Mason University
Dr. Elliot Axelband, University of Southern California
Dr. Dennis Buede, Innovative Decisions Inc
Dr. Dave Evans, Aerospace Institute
Dr. Levis and the Subcommittee on Systems Engineering crafted the idea of publishing
these case studies, reviewed several proposals, selected four systems as the initial cases for study,
and continued to provide guidance throughout their development. The Subcommittee members
have been a guiding force to charter, review, and approve the work of the authors. The four case
studies produced in that series were the C-5A Galaxy, the F-111, the Hubble Space Telescope,
and the Theater Battle Management Core System. The second series of case studies produced
were the B-2 Spirit Stealth Bomber and the Joint Air-To-Surface Standoff Missile (JASSM).
This third series includes the Global Positioning System (GPS).
[Pending] Approved for Public Release; Distribution Unlimited
The views expressed in this Case Study are those of the author(s) and do not reflect the
official policy or position of the United States Air Force, the Department of Defense, or the
United States Government
2
Foreword
At the direction of the Secretary of the Air Force, Dr. James G. Roche, the Air Force
Institute of Technology (AFIT) established a Center for Systems Engineering (CSE) at its Wright
Patterson AFB, campus in
20
02. With academic oversight by a Subcommittee on Systems Engi-
neering, chaired by Air Force Chief Scientist Dr. Alex Lewis, the CSE was tasked to develop case
studies focusing on the application of systems engineering principles within various Air Force
programs. The committee drafted an initial case outline and learning objectives, and suggested
the use of the Friedman-Sage Framework to guide overall analysis.
The CSE contracted for management support with Universal Technology Corporation
(UTC) in July 2003. Principal investigators for the four case studies published in the initial
series included Mr. John Griffin for the C-5A, Dr. G. Keith Richey for the F-111, Mr. James
Mattice for the Hubble Telescope, and Mr. Josh Collens for the Theater Battle Management Core
System. These cases were published in 2004. Two additional case studies have since been
added to this series with the principal investigators being Mr. John Griffin for the B-2 and Dr.
Bill Stockman for the JASSM. All case studies (with the exception of JASSM) are available on
the CSE website [http://www.afit.edu/cse].
The Department of Defense continues to develop and acquire joint complex systems that
deliver needed capabilities demanded by our warfighter. Systems engineering is the technical
and technical management process that focuses explicitly on delivering and sustaining robust,
high-quality, affordable products. The Air Force leadership, from the Secretary of the Air Force
through the Commander of the Air Force Materiel Command, has collectively stated the need to
mature a sound systems engineering process throughout the Air Force.
Plans exist for future case studies focusing on other areas. Suggestions have included
other Joint-service programs, logistics-led programs, science and technology/laboratory efforts,
additional aircraft programs, and successful commercial systems.
As we uncovered historical facts and conducted key interviews with program managers
and chief engineers, both within the government and those working for the various prime and
subcontractors, we concluded that systems programs face similar challenges today. Applicable
systems engineering principles and the effects of communication and the environment continue
to challenge our ability to provide a balanced technical solution. We look forward to your
comments on this GPS case, our other CSE published studies, and future case studies.
GEORGE E. MOONEY, SES
Director, Air Force Center for Systems Engineering
Air Force Institute of Technology
http://www.afit.edu/cse
3
http://www.afit.edu/cse
Acknowledgements
To those who contributed to this report:
The authors would like to acknowledge the special contributions of people who dedicated
their time and energy to make this report accurate and complete. We offer our sincere appreciation
to all people listed in Appendix 4 who volunteered their time and insight during the interviews,
especially Col. (ret.) Rick Reaser. He identified an extensive list of potential interviewees at the
Joint Program Office (JPO), other government agencies and contractors, and also provided
several early reference documents that allowed the authors to gain significant insight into the
systems engineering process when the “well appeared dry.” Capt. Steaven Meyer, GPS JPO,
helped set up the capability to obtain limited access to the GPS website, which provided much-
needed program baseline documents. We send a special thanks to Mr. Frank Smith, Ms. Vicki
Hellmund, Andrea Snell, and Ms. Niki Maxwell from the University of Dayton Research
Institute. Mr. Smith helped “in a pinch” to conduct research and interviews and provide insight
into the GPS program in order to keep the study on track. Ms. Maxwell’s effort in editing and
formatting resulted in a polished study report. Our apologies and thanks to Doug Robertson
who, “being within arm’s reach”, was pestered with GPS trivial questions for clarification.
We also provide a special thank you and note of appreciation to our AFIT Project
Leaders, Maj. Eileen Pimentel and Mr. Randy Bullard, who provided guidance to the authors,
along with continuous motivation.
To those who made GPS work:
We would also like to take this opportunity to express gratitude to all the people in the
program, especially the systems engineers and design engineers at Rockwell, IBM, Rockwell
Collins, Magnavox, General Dynamics, the vendors, the Naval Research Laboratory, the US
Naval Observatory, Aerospace Corporation, the GPS Joint Program Office and the many other
supporting agencies. They took the glimmer of an idea and delivered an outstanding, precise
navigation capability that has not only served the US military, but military internationally and
the commercial world, spanning so many other applications beyond navigation.
We owe the people of the GPS Program a great deal of gratitude. They made sacrifices
in time, some in careers, and dedicated themselves as a team to bring a vision to reality. They
worked in anonymity, never asking for credit. And without fanfare, they changed everything.
Thanks.
Patrick J. O’Brien
John M. Griffin
4
Table of Contents
Preface ……………………………………………………………………………………………………….. 2
Foreword…………………………………………………………………………………………………….. 3
Acknowledgements ………………………………………………………………………………………. 4
Table of Contents …………………………………………………………………………………………
5
List of Figures ……………………………………………………………………………………………..
7
1.
……………………………………………..
9
1.1 General Systems Engineering Process …………………………………………………………………… 9
1.1.1 Introduction…………………………………………………………………………………………………….. 9
1.1.2 Case Study ……………………………………………………………………………………………………..
11
1.1.3 Framework for Analysis …………………………………………………………………………………..
12
1.2 GPS Friedman-Sage Matrix …………………………………………………………………………………
13
…………………………………………………………………….
14
2.1 Mission ………………………………………………………………………………………………………………. 14
2.2 Features ……………………………………………………………………………………………………………… 14
2.3 System Design …………………………………………………………………………………………………….. 14
2.3.1 Space Vehicle ………………………………………………………………………………………………… 14
2.3.2 User Equipment ……………………………………………………………………………………………..
17
2.3.3 Control Segment……………………………………………………………………………………………..
18
2.3.4 Nuclear Detection System (NDS) ………………………………………………………………………
19
2.3.5 “NAVSTAR/GPS” ………………………………………………………………………………………….. 19
……………………………………………………………. 20
3.1 Early Programs ………………………………………………………………………………………………….. 20
3.2 Establishment of a Joint Program ………………………………………………………………………..
25
3.3 Concept/Validation Phase (Phase I) ……………………………………………………………………..
28
3.3.1 Objectives ……………………………………………………………………………………………………… 28
3.3.2 Requirements …………………………………………………………………………………………………. 29
3.3.3 Acquisition Strategy ………………………………………………………………………………………..
31
3.3.4 Trade Studies …………………………………………………………………………………………………
33
3.3.5 Risk Mitigation ……………………………………………………………………………………………….
35
3.3.6 System Integration ………………………………………………………………………………………….
38
3.3.7 Systems Engineering ……………………………………………………………………………………….
42
3.3.8 DSARC II ………………………………………………………………………………………………………
45
3.4 System Development (Phase II, Block I) ………………………………………………………………. 45
3.4.1 Objectives ……………………………………………………………………………………………………… 45
3.4.2 Systems Engineering (JPO) ……………………………………………………………………………..
46
3.4.3 Interface Requirements …………………………………………………………………………………… 46
3.4.4 Budgetary Impacts to Functional Baseline …………………………………………………………
47
3.4.5 Rockwell International Systems Engineering ……………………………………………………..
48
3.4.6 Atomic Clocks ………………………………………………………………………………………………..
51
3.4.7 Control Segment……………………………………………………………………………………………..
53
3.4.8 User Equipment ……………………………………………………………………………………………..
54
3.4.9 Design Reviews ………………………………………………………………………………………………
56
3.4.10 System Integration ……………………………………………………………………………………….. 56
5
3.4.11 ICWG …………………………………………………………………………………………………………. 56
3.5 Production and Deployment (Phase III, Block II/IIA) …………………………………………..
57
3.5.1 Objective ………………………………………………………………………………………………………. 57
3.5.2 Acquisition Strategy ……………………………………………………………………………………….. 57
3.5.3 Nuclear Detection System ……………………………………………………………………………….. 57
3.5.4 Shuttle Impact to Functional Baseline ……………………………………………………………….
59
3.5.5 User Equipment (UE) Development Testing Effects …………………………………………….
6
2
3.5.6 Control Segment……………………………………………………………………………………………..
63
3.5.7 Requirements Validation & Verification ……………………………………………………………
67
3.6. Replenishment Program Block IIR …………………………………………………………………….. 67
3.6.1 Objective ………………………………………………………………………………………………………. 67
3.6.2 Acquisition Strategy ……………………………………………………………………………………….. 67
3.6.3 Requirements ………………………………………………………………………………………………….
68
3.6.4 Critical Design Reviews ………………………………………………………………………………….. 68
3.6.5 User Equipment ……………………………………………………………………………………………..
69
3.7 Full Operational Capability …………………………………………………………………………………
70
………………………………………………………………………………………….
72
……………………………………………………..
73
……………………………………………………………………………………
74
………………………………………………………………………
78
……………………………….
79
……………………………………………………………….. 70
………………………………………………………………………………
72
………………………………………………………. 73
………………………….
123
……………………………………………….123
Appendix 6 – GPS JPO Organization Chart ……………………………………………….
124
………………………………..
125
6
List of Figures
Figure 1-1. The Systems Engineering Process, Defense Acquisition University ………………………..
10
Figure 2-1.
24
-Spaced-Based Satellite Constellation (Ref. 46) ……………………………………………….
15
Figure 2-2. Navigational Technology Satellite (Ref.
23
) ………………………………………………………
16
Figure 2-3. Block I GPS Satellite …………………………………………………………………………………….. 16
Figure 2-4. Block IIA GPS Satellite …………………………………………………………………………………. 16
Figure 2-5. Block IIR GPS Satellite ………………………………………………………………………………… 17
Figure 2-6. Block IIF GPS Satellite ………………………………………………………………………………… 17
Figure 2-7. Rockwell Collins Precision Lightweight GPS Receiver (PLGR) (left) and Defense
Advanced GPS Receiver (DAGR) (right) a later version of the PLGR (Ref. 48, 45) ………………. 17
Figure 2-8. Magellan Marine Receiver (Ref. 46) ……………………………………………………………… 18
Figure 2-9. Control Segment (Ref. 42) ……………………………………………………………………………. 19
Figure 2-10. NDS System Segments (Ref.
49
)…………………………………………………………………… 19
Figure 3-1. Program Schedule (Ref. 13) ………………………………………………………………………….
27
Figure 3-2. System Interfaces (Ref. 28) ……………………………………………………………………………
30
Figure 3-3. Rockwell Collins GDM (Ref. 47) ……………………………………………………………………
32
Figure 3-4. Planned Constellation Development before 1974. Proof of Concept has 6 Block I
satellites in 2 planes. Build up to 24 Block II satellites in 3 planes (Ref. 18) …………………………
34
Figure 3-5. NTS-2 Command and Telemetry Links (Ref. 1) ………………………………………………..
36
Figure 3-6. NTS-2 Satellite (Ref. 23) ………………………………………………………………………………. 36
Figure 3-7. Phase 1 YPG Test Results (Ref. 51) ……………………………………………………………….. 38
Figure 3-8. GPS JPO Agency/Contractor Interfaces …………………………………………………………
39
Figure 3-9. Phase I Specification Tree (Ref. 28) ……………………………………………………………….
40
Figure 3-10. Phase II Specification Tree (Ref.
41
) ……………………………………………………………. 40
Figure 3-11. Interface Control Documents (chart from 2005 JPO SE briefing that captures the
breadth of some 200 ICDs) (Ref. 29) ……………………………………………………………………………….. 42
Figure 3-12. GPS Functional Flow Diagram (Ref. 28) ………………………………………………………
43
Figure 3-13. Block II Cesium Atomic Clock (Ref.
50
) ………………………………………………………..
52
Figure 3-14. Block IIA Satellite ……………………………………………………………………………………… 59
Figure 3-15. Space Segment System Relationship (Ref.
44
) ………………………………………………..
60
Figure 3-16. Delta II Launch of Block II Satellites ……………………………………………………………
62
Figure 3-17. Rockwell Collins Manpack (Ref. 47) ……………………………………………………………. 63
Figure 3-18. Operational Control System Top Level System Diagram (Ref. 43) ……………………
65
Figure 3-19. 24-Satellite Constellation (Ref. 49) ……………………………………………………………… 67
Figure 3-20. DoD of UE Family Tree Collins Manpack (Ref. 35) ………………………………………. 70
7
List of Tables
Table 1-1. A Framework of Key Systems Engineering Concepts and Responsibilities ……………….. 13
Table 3-1. Major Events in Navigation and GPS Events/Milestones ……………………………………
21
Table 3-2. Expected GPS Performance (Ref. 13) ……………………………………………………………….
26
Table 3-3. Proposed Classes of User Equipment (Ref. 13) ………………………………………………… 28
Table 3-4. Phase I Major Contractors (Ref. 4) …………………………………………………………………. 31
Table 3-5. General Dynamics Phase I Trade Studies (Ref. 19) …………………………………………… 33
Table 3-6. GPS PPS System Error Range Budget (Ref. 42)* ……………………………………………… 44
Table 3-7. GPS Time Error Budget (Ref. 42) …………………………………………………………………… 45
Table 3-8. GPS Atomic Clocks [8, Fruehauf, 21 Reaser, 30 White] ……………………………………. 53
Table 3-9. Army and PLGR Requirements (Ref. 32) System Description …………………………….. 69
8
1. SYSTEMS ENGINEERING PRINCIPLES
1.1 General Systems Engineering Process
1.1.1 Introduction
The Department of Defense continues to develop and acquire joint systems and deliver
needed capabilities to the warfighter. With a constant objective to improve and mature the acquisi-
tion process, it continues to pursue new and creative methodologies to purchase these technically
complex systems. A sound systems engineering process, focused explicitly on delivering and
sustaining robust, high-quality, affordable products that meet the needs of customers and stake-
holders must continue to evolve and mature. Systems engineering is the technical and technical
management process that results in delivered products and systems that exhibit the best balance of
cost and performance. The process must operate effectively with desired mission-level
capabilities, establish system-level requirements, allocate these down to the lowest level of the
design, and ensure validation and verification of performance, while meeting the cost and schedule
constraints.
The systems engineering process changes as the program progresses from one phase to
the next, as do tools and procedures. The process also changes over the decades, maturing,
growing, and evolving from the base established during the conduct of past programs. Systems
engineering has a long history. Examples can be found demonstrating application of effective
engineering and engineering management, as well as poorly applied, but well-defined processes.
Throughout the many decades during which systems engineering has emerged as a discipline,
many practices, processes, heuristics, and tools have been developed, documented, and applied.
System requirements are critical to all facets of successful system program development.
First, system development must proceed from a well-developed set of requirements. Second,
regardless of the evolutionary acquisition approach, the system requirements must flow down to
all subsystems and lower-level components. And third, the system requirements must be stable,
balanced, and must properly reflect all activities in all intended environments. However, system
requirements are not unchangeable. As the system design proceeds, if a requirement or set of
requirements is proving excessively expensive to satisfy, the process must rebalance schedule,
cost, and performance by changing or modifying the requirements or set of requirements.
Systems engineering includes making key system and design trades early in the process to
establish the system architecture. These architectural artifacts can depict any new system, legacy
system, modifications thereto, introduction of new technologies, and overall system-level behavior
and performance. Modeling and simulation are generally employed to organize and assess
architectural alternatives at this stage. System and subsystem design follows the functional
architecture. System architectures are modified if elements are too risky, expensive, or time-
consuming. Both newer object-oriented analysis and design, and classic structured analysis
using functional decomposition and information flows/data modeling occur. Design proceeds
logically using key design reviews, tradeoff analysis, and prototyping to reduce any high-risk
technology areas.
9
Important to the efficient decomposition and creation of functional and physical archi-
tectural designs are the management of interfaces and the integration of subsystems. Interface
management and integration is applied to subsystems within a system or across a large, complex
system of systems. Once a solution is planned, analyzed, designed, and constructed, validation
and verification take place to ensure satisfaction of requirements. Definition of test criteria,
measures of effectiveness (MOEs), and measures of performance (MOPs) are established as part
of the requirements process, taking place well before any component/subsystem assembly design
and construction occurs.
There are several excellent representations of the systems engineering process presented
in the literature. These depictions present the current state of the art in maturity and evaluation
of the systems engineering process. One can find systems engineering process definitions,
guides, and handbooks from the International Council on Systems Engineering (INCOSE),
European Industrial Association (EIA), Institute of Electrical and Electronics Engineers (IEEE),
and various Department of Defense (DoD) agencies and organizations. They show the process as
it should be applied by today’s experienced practitioner. One of these processes, long used by
the Defense Acquisition University (DAU), is depicted in Figure 1-1. It should be noted that this
model is not accomplished in a single pass. This iterative and nested process gets repeated to the
lowest level of definition of the design and its interfaces.
Figure 1-1. The Systems Engineering Process, Defense Acquisition University
The DAU model, like all others, has been documented in the last two decades, and has
expanded and developed to reflect a changing environment. Systems are becoming increasingly
complex internally and more interconnected externally. The process used to develop aircraft and
10
systems of the past was effective at the time. It served the needs of the practitioners and resulted
in many successful systems in our inventory. Notwithstanding, the cost and schedule
performance of the past programs are replete with examples of well-managed programs and ones
with less-stellar execution. As the nation entered the 1980s and 1990s, large DoD and
commercial acquisitions experienced overrunning costs and slipping schedules. The aerospace
industry and its organizations were becoming larger and were more geographically and culturally
distributed. Large aerospace companies have worked diligently to establish common systems
engineering practices across their enterprises. However, because of the mega-trend of teaming in
large (and some small) programs, these common practices must be understood and used beyond
the enterprise and to multiple corporations. It is essential that the systems engineering process
govern integration, balance, allocation, and verification, and be useful to the entire program team
down to the design and interface level.
Today, many factors overshadow new acquisition; including system-of-systems (SoS) con-
text, network centric warfare and operations, and rapid growth in information technology. These
factors are driving a more sophisticated systems engineering process with more complex and
capable features, along with new tools and procedures. One area of increased focus of the sys-
tems engineering process is the informational systems architectural definitions used during system
analysis. This process, described in DoD Architectural Framework (DoDAF), emphasizes greater
reliance on reusable architectural views describing the system context and concept of operations,
interoperability, information and data flows, and network service-oriented characteristics.
1.1.2 Case Study
The systems engineering process to be used in today’s complex system and system-of-
systems is a process matured and founded on principles developed in the past. Examination of
systems engineering principles used on programs, both past and present, can provide a wealth of
lessons to be used in applying and understanding today’s process. It was this thinking that led to
the construction of the AFIT CSE case studies.
The purpose of developing detailed case studies is to support the teaching of systems
engineering principles. They facilitate learning by emphasizing to the student the long-term conse-
quences of the systems engineering and programmatic decisions on program success. The systems
engineering case studies assist in discussion of both successful and unsuccessful methodologies,
processes, principles, tools and decision material to assess the outcome of alternatives at the
program/system level. In addition, the importance of using skills from multiple professions and
engineering disciplines, and collecting, assessing, and integrating varied functional data is empha-
sized. When they are taken together, the student is provided real-world detailed examples of
how the process attempts to balance cost, schedule, and performance.
The utilization and mis-utilization of systems engineering principles are highlighted, with
special emphasis on the conditions that foster and impede good systems engineering practice.
Case studies are used to illustrate both good and bad implementation of acquisition management
and learning principles, such as:
• Every system provides a satisfactory balanced and effective product to a customer
• Effective requirements analysis was applied
• Consistent and rigorous applications of systems engineering management was applied
11
• Effective test planning was accomplished
• There were effective major technical program reviews
• Continuous risk assessments and management was implemented
• Cost estimates and policies were reliable
• Disciplined application of configuration management used
• A rigorous system boundary was defined
• Disciplined methodologies for complex systems used
• Problem solving incorporated understanding of the system within the bigger
environment (customer’s customer)
The systems engineering process transforms an operational need into a system or several
system-of-systems elements. Architectural elements of the system are allocated and translated into
detailed design requirements by the systems engineering process. The systems engineering
process, from the identification of the need to the development and utilization of the product,
must continuously integrate and balance the requirements, cost, and schedule to provide an
operationally effective system throughout its life cycle. Systems engineering case studies
highlight the various interfaces and communications to achieve this balance, which include:
• The program manager/systems engineering interface is essential between the operational
user and developer (acquirer) to translate the needs into performance requirements for
the system and subsystems.
• The government/contractor interface is essential for the practice of systems engineering
to translate and allocate the performance requirements into detailed requirements.
• The developer (acquirer)/user interface within the project is essential for the systems
engineering practice of integration and balance.
The systems engineering process must manage risk, both known and unknown, as well as
both internal and external. Risk management will specifically capture and access risk factors and
their impact, for example, uncontrollable influences such as actions of Congress, changes in fund-
ing, new instructions/policies, changing stakeholders, changing user requirements, or changing
contractor and government staffing levels. Case studies can clearly illustrate how risk manage-
ment is executed during actual programs.
Lastly, the systems engineering process must respond to “Mega Trends” in the systems
engineering discipline itself, as the nature of systems engineering and related practices do vary
with time. Case studies can suggest new systems engineering process ideas and, on the other
hand, serve as reminders of the systems engineering essentials needed to ensure program success.
1.1.3 Framework for Analysis
The systems engineering case studies published by AFIT employ the Friedman-Sage
framework and matrix as the baseline assessment tool to evaluate the conduct of the systems
engineering process for the topic program. The framework and the derived matrix can play an
important role in developing case studies in systems engineering and systems management,
especially case studies that involve systems acquisition. The Friedman-Sage framework is a
nine-row by three-column matrix shown in Table 1-1.
12
Table 1-1. A Framework of Key Systems Engineering Concepts and Responsibilities
Concept Domain Responsibility Domain
1. Contractor
Responsibility
2. Shared
Responsibility
3. Government
Responsibility
A. Requirements Definition and Management
B. Systems Architecture and Conceptual Design
C System and Subsystem Detailed Design and
Implementation
D. Systems Integration and Interface
E. Validation and Verification
F. Deployment and Post Deployment
G. Life Cycle Support
H. Risk Assessment and Management
I. System and Program Management
Six of the nine concept domain areas in Table 1-1 represent phases in the systems engineering
lifecycle:
A. Requirements Definition and Management
B. Systems Architecture and Conceptual Design
C. Detailed System and Subsystem Design and Implementation
D. Systems Integration and Interface
E. Validation and Verification
F. Deployment and Post-Deployment
Three of the nine concept areas represent necessary process and systems management support:
G. Life Cycle Support
H. Risk Assessment and Management
I. System and Program Management
While other concepts could have been identified, the Friedman-Sage framework suggests
these nine are the most relevant to systems engineering, in that they cover the essential life cycle
processes in the systems engineering acquisition and the systems management support in the
conduct of the process. Most other areas that are identified during the development of the matrix
appear to be subsets of one of these. The three columns of this two-dimensional framework
represent the responsibilities and perspectives of government and contractor, and the shared
responsibilities between the government and the contractor. In teaching systems engineering in
DoD, there has previously been little distinction between the duties and responsibilities of the
government and industry activities. While the government has the responsibility in all nine
concept domains, its primary objective is establishing mission requirements.
1.2 GPS Friedman-Sage Matrix
The Friedman-Sage matrix is used herein retrospectively, as an assessment tool for the
systems engineering process for the GPS program. The authors selection of learning principles
is reflected in the Part 1 Executive Summary of this case.
13
2. SYSTEM DESCRIPTION
2.1 Mission
The Global Positioning System (GPS) is a satellite-based radio navigation system. It
provides suitably equipped users the capability to precisely determine three-dimensional position
and velocity and time information on a global basis (Ref. 12). The capability was developed to
provide the United States and DoD with worldwide navigation, position, and timing capabilities
to support military operations by enhancing ground, sea, and air warfighting efficiencies. How-
ever, by presidential directive, it was officially made available to the civilian community in
1983.1 GPS also provides the capability to conduct time transfer for synchronization purposes
through the use of precise time standards. GPS supports a secondary mission to provide a highly
survivable military capability to detect, locate, and report nuclear detonations in the Earth’s
atmosphere and in near-Earth space in real time.
2.2 Features
“GPS is a highly accurate, passive, all-weather 24-hour, worldwide navigational system
(Ref. 23).” Each GPS satellite continuously transmits precise ranging signals at two L-band fre-
quencies: L1 and L2, where L1 = 1575.42 MHz and L2 = 1227.6 MHz. Trilateration is the
method of determining the relative positions of the user.
GPS provides Nuclear Detonation Detection System (NDS) capability. With NDS on-
board the satellites, the system can detect nuclear detonation (NUDEC) on or above the surface.
2.3 System Design
GPS consists of three major segments: the Space Vehicle (SV), the User Equipment (UE),
and the Control Station (CS).
2.3.1 Space Vehicle
The space vehicle segment consists of a system of 24 space-based satellites, of which
three are spares (see Figure 2-1 for satellite constellation). The Block II satellites are configured
in a constellation of six equally spaced orbital planes, inclined at
55
degrees and with four
satellites in each plane. The spares are deployed in every other orbital plane. The satellite
orbital radius is 26,561.7 km. Each satellite has a 12-hour orbit. Precise time is provided by a
redundant system of rubidium and/or cesium atomic clocks on-board the SV.
Each satellite is capable of continuously transmitting L1 and L2 signals for navigation
and timing, and L3 signal for nuclear detonation data (see Section 2.3.4 for further details). It is
also capable of receiving commands and data from the master control station, and data from
remote antennas via S-band transmissions.
1 GPS was always available to the civilian community. The GPS JPO worked to make the civilian community a part
of GPS before the directive was issued. User charges were in effect for a very short period. President Reagan’s
directive for free commercial use of GPS after the Korean aircraft was shot down culminated several ongoing efforts
to eliminate the charge and make GPS free to the civilian community [25, Scheerer].
14
Figure 2-1. 24-Spaced-Based Satellite Constellation (Ref. 46)
The satellites transmit timing and navigational data on the two L-band frequencies, L1
and L2. Three pseudo-random noise (PRN) ranging codes are in use:
• The course/acquisition (C/A)-code has a 1.023 MHz chip rate, a period of 1 millisecond
(ms), and is used primarily to acquire the P-code. Each satellite has a unique (C/A)-
code. Literature also uses the term “clear/acquisition” for C/A. Both appear acceptable.
• The precision (P)-code has a 10.23 MHz chipping rate, a period of days, and is the
principal navigation ranging military code.
• The (Y)-code is used in place of the (P)-code whenever the anti-spoofing (A-S) mode
of operation is activated. Contrary to the (C/A)-code, each satellite has the same (P)-
code, which is almost a year long, but each satellite is assigned a unique (P)-code that
is reset every seven days. In this mode, the (P)- and (Y)-code functionality is often
referred to the P(Y)-code. Modulated on the above codes is the 50 bps data stream. P-
and P(Y)-code are for military use only.
The C/A-code is available on the L1 frequency only; however, future satellite constel-
lations will carry added signals, including a (C/A)-code on L2 and the P-code on both L1 and L2.
The various satellites all transmit on the same frequencies, L1 and L2, but with individual (C/A)-
code assignments. The (C/A)-code is available to all civilian users.
Due to the spread spectrum characteristic of the signals, the system provides a large mar-
gin of resistance to interference. Each satellite transmits a navigation message containing its
orbital elements, clock behavior, system time, and status messages. In addition, an almanac is
also provided, which gives the approximate data for each active satellite. This allows the user set
to find all satellites once the first has been acquired.
There are four sets of satellite efforts discussed in this report: The Navigational Tech-
nology Satellites (NTS) launched in Phase I during concept validation phase (Figure 2.2), the
Block I development satellites (Figure 2-3), the Block II/IIA production satellites (Figure 2.4),
and the Block IIR (Figure 2-5). The Block IIF replacement satellites (Figure 2.6) photograph is
provided for additional information.
15
Figure 2-2. Navigational Technology Satellite (Ref. 23)
Pr
ov
id
ed
b
y
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ug
o
Fr
ue
ha
uf
Figure 2-3. Block I GPS Satellite
Pr
ov
id
ed
b
y
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ug
o
Fr
ue
ha
uf
Figure 2-4. Block IIA GPS Satellite
16
Pr
ov
id
ed
b
y
H
ug
o
Fr
ue
ha
uf
Figure 2-5. Block IIR GPS Satellite
P
ro
vi
de
d
by
H
ug
o
Fr
ue
ha
uf
Figure 2-6. Block IIF GPS Satellite
2.3.2 User Equipment
In general, the user equipment (receiver) compares the time a signal was transmitted by a
satellite with the time it was received. The time difference, along with the location of the
satellites, allows the receiver to determine the user location. Signals from a minimum of four
different satellites are required to determine a three-dimensional position. The user equipment
(receiver) generally consists of an antenna assembly, receiver, data processor, control/display unit,
power supply, and interface unit. There are numerous applications represented by user equip-
ment, including those shown in Figures 2.7 and 2.8.
Figure 2-7. Rockwell Collins Precision Lightweight GPS Receiver (PLGR) (left) and Defense
Advanced GPS Receiver (DAGR) (right) a later version of the PLGR (Ref. 48, 45)
17
Figure 2-8. Magellan Marine Receiver (Ref. 46)
2.3.3 Control Segment
The control segment commands, uploads system and control data to, monitors the health
of, and tracks the space vehicle to validate ephemeris data. The control segment consists of a
Master Control Station (MCS) located at Colorado Springs (Schriever AFB); five remote moni-
tor stations which are located in Hawaii, Ascension Island, Diego Garcia, Kwajalein, and Colo-
rado Springs; three ground antennas which are located at Ascension Island, Diego Garcia, and
Kwajalein; and a Pre-Launch Compatibility Station, which can also function as a ground antenna,
located at Cape Canaveral AFS. Figure 3-9 illustrates the elements of the control segment (CS).
The remote monitor stations track each GPS satellite in orbit, monitor the SV’s naviga-
tional signals and health information, and simultaneously relay this information to the MCS.
Each monitor station has the ability to track up to 11 satellites at once on L1 and L2 signals.
The ground antennas have the capability to upload time corrections and navigation data
to the satellites (one at a time per ground antenna) via S-band transmissions. The ground anten-
nas also command the satellites and receive satellite telemetry data.
The ground equipment for receipt of precise time data from a satellite for the US Naval
Observatory (USNO) is located in the Washington DC area. There is a backup precise time moni-
toring facility at Schriever AFB [31, Winkler]. USNO monitors the time transfer performance
and provides data to the MCS on GPS time relative to USNO Coordinated Universal Time
(UTC). The MCS is responsible for providing offset information to ensure that the GPS time can
be maintained within a specified accuracy to UTC when the offset corrections are applied. Note
that the SV atomic clocks require periodic updates, as the clocks are only relatively stable.
The ground equipment for receipt of the nuclear detection data via L3 was not the re-
sponsibility of the GPS Joint Program Office. The GPS control segment was responsible for
maintaining the required environment for the Integrated Operational Nuclear Detonation
(NUDET) Detection Systems (IONDS) and the Nuclear Detection System (NDS) sensor.
18
Figure 2-9. Control Segment (Ref. 42)
2.3.4 Nuclear Detection System (NDS)
A satellite detecting a NUDET processes the data and crosslinks it to other satellites via
Ultra-High Frequency (UHF). All SVs with NUDET data transmit to the NDS User Segment via
a specific L3 frequency. The satellites also transmit NUDET data over the Space-Ground Link
Subsystem (SGLS) operating on S-band. Figure 2-10 depicts the NDS system segments.
Figure 2-10. NDS System Segments (Ref. 49)
2.3.5 “NAVSTAR/GPS”
Dr. Brad Parkinson (Col., ret.) relates the title Global Positioning System “…originated
with Major General Hank Stelling, who was the Director of Space for the U.S. Air Force DCS
Research and Development (RDS) in the early 1970s” (Ref. 6). The title NAVSTAR was suggested
by Mr. John Walsh, an Associate Director of Defense Development, Research and Engineering
(DDR&E) who made decisions with respect to the program budget. Within this report, the term
“Global Positioning System” or “GPS” will commonly be used.
19
3. GPS PROGRAM EXECUTION
The GPS program traces it heritage from the early 1960s when Air Force Systems Com-
mand initiated satellite-based navigation systems analysis, conducted by Aerospace Corporation.
The case study follows the execution of the GPS program from the inception of the idea to the
Full Operational Capability (FOC) release, 27 Apr 1995. The discussion will cover the transition
from concept through development, production, and operational capability release. The concen-
tration of the case study is not limited to any particular period, and the learning principles come
from various times throughout the program’s schedule.
Table 3-1 shows the events and milestones key to the development of the concept, produc-
tion, and the eventual operational capability. This table will be the reference for keeping dates
and events in the proper chronological context. The term “Block” applies to certain phases of
the program. These will be discussed in greater detail later in the report. However, to provide
insight into the table, the following explanation is provided:
• Navigational Technology Satellites (NTS): Concept validation phase (also known as Phase I)
• Block I Satellites, also known as Navigational Development Satellites (NDS): System Veri-
fication phase of GPS Block I in-orbit performance validation (also known as Phase II)
• Block II/IIA Satellites: Production phase (also known as Phase III)
• Block IIR Satellites: Replacement operational satellites
3.1 Early Programs
The GPS program evolved as a result of several navigation studies, technology demon-
strations, and operational capabilities. Some of the key efforts that helped establish potential
needs, and the technological feasibility to initiate the NAVSTAR/GPS, are briefly discussed to
provide an appreciation of those efforts and how they affected the systematic approach used by
the GPS Program.
Sea and air navigation needs during World War II resulted in two systems being devel-
oped: the United Kingdom GEE and the United States Long Range Navigation (LORAN) which
was developed from the GEE technology. These were the first navigational systems to use
multiple radio signals and measure the Doppler Effect (i.e., the difference in the arrival of
signals), as a means of determining position. After the Russian Sputnik I launch in 1957, there were
several efforts looking into space applications. Soon after the Sputnik I launch, Drs. Geier and
Weiffenbach at John Hopkins University Applied Research Laboratory (ARL) conducted a study
of the Sputnik space-generated signals. The study concluded that a complete set of orbit
parameters for a near-earth satellite could be inferred to useful accuracy from a single set of
Doppler shift data (single pass from horizon to horizon). Applying “the inverse problem”
(knowing the orbit), the ground location could be predicted. ARL was aware of the Navy’s need
to precisely determine the location of Polaris submarines as an initial condition for Polaris
launch. After discussions with the Navy, ARL submitted a proposal to the Navy in 1958 for the
TRANSIT Navigational System based upon the technical effort on orbit ephemeredes algorithms
they devolved. Out of this effort, the Polaris program provided initial sponsorship.
20
Table 3-1. Major Events in Navigation and GPS Events/Milestones
Mar 1942 British GEE System became operational
1941 – 1943 Long Range Navigation (LORAN) developed and operationally implemented
1957 Demonstration of establishing satellite ephemeris through measurement of Doppler shift by Applied Research Laboratory (Ref. 8)
13 April
1960 First navigation satellite TRANSIT launched by the Navy
1963 Air Force Project 621B established
5 Dec 1963 First operational TRANSIT satellite launched
1964 TIMATION begins development under Roger Easton at the Naval Research Laboratory
1967 First TIMATION satellite launched by Navy
1967 TRANSIT fully operational
1968 Navigation Satellite Executive Group (NAVSEG) established among three services within DoD
31 Aug 19
71
DoD Directive listed and confirmed US Naval Observatory for establishing, coordinating, and maintaining time and time interval
19 Jun 1972 Defense Navigation Satellite System Program (DNSSP) Management Directive signed (later evolved into GPS Program)
13 Dec 1973 Defense System Acquisition and Review Board (DSARC) approval to proceed with the GPS program
8 Aug 19
74
Block I Satellite Contract Award to Rockwell International
Sep 1974 Block I User Equipments and Ground Station Contract Award to General Dynamics
14 Jul 1974 Navigational Technology Satellite (NTS) I (a refurbished TIMATION II) satellite with first atomic clock (two Rubidium Clocks) launched
June 19
75
Contract Award to Texas Instruments for Manpack & Aircraft Receivers
22 Feb 1978 First Block I Navigation Development Satellite (NDS) is launched
5 Jun 1979 DSARC II approval to proceed into Full Scale Development (FSD)
Fall 1979 Decision from the Pentagon to cut constellation from 24 to 18 due to DoD funding cutback
26 Apr 19
80
First GPS satellite to carry the Integrated Operational Nuclear Detection System (IONDS) launched
16 Sept 19
83
President Reagan directs GPS become available to civilian community at a no-charge basis
May 1983 Block II satellite contract award to Rockwell International
April 19
85
First GPS user equipment production contract
Oct 1985 Seventh and last Block I satellite launched
28 Jan 19
86
Space Shuttle Challenger accident
Jun 1986 DSARC IIIA approved to proceed into production
14 Feb 19
89
First Block II production satellite launched
21 Jun 1989 Block IIR Satellite contract award to GE Astro Space division
26 Nov 19
90
Selective Availability activated per Federal Radio Navigation Plan
26 Nov 1990 First Block IIA production satellite with Nuclear Detection Systems capability launched
8 Dec 19
93
Secretary of Defense declares NAVSTAR GPS Initial Operation Capability (IOC) with a constellation of Block I/II/IIA satellites
27 Apr 19
95
HQ Air Force Space Command declares GPS fully operational with Block II/IIA satellites
29 Mar 19
96
Presidential Policy on GPS – discontinue Selective Availability within a decade
31 Dec 1996 Navy terminates TRANSIT operations
6 Nov 19
97
Last block IIA satellite launched
23 July 1997 First successful Block IIR satellite launch
1 May 2000 Selective Availability function discontinued
21
The Advanced Research Projects Agency (ARPA) became the formal sponsor of the pro-
gram later in 1958, supported by the Navy’s Strategic System Program Office. Dr. Richard
Kirschner managed the APL program. The operational configuration was six satellites in polar
orbit at approximately 600 nautical miles. Satellite ephemeris was broadcasted, and the provided
navigational solution was two-dimensional. Additionally, the receiver had to know its own
altitude and correct for platform velocity. Consequently, this system was not suited for aircraft
applications. Navigational accuracy was approximately 100-meter Circular Error Probable
(CEP). Even though the system was designed for a two- to three-year life, some of the systems
attained up to 16 years of service. This system became available to the civilian community in
1967. “TRANSIT pioneered many areas of space technology, including stabilization systems,
advancing time and frequency standards, multiple spacecraft launchings, and the first electronic
memory computer in space” (Ref. 10). Near- and real-time orbit prediction, led by Messrs. Hill
and Anderle of the Naval Surface Weapons Center (NSWC), was a key technology that
TRANSIT matured that was valuable to the GPS [17, Parkinson].
Aerospace Corporation was conducting studies looking into military applications, most
being space-based concepts. One of these studies, Project 57, encompassed the use of satellites
for improving navigation for fast-moving vehicles in three dimensions. It was “in this study that
the concept for GPS was born” (Ref. 8). The Air Force encouraged Aerospace Corp. to continue
these studies stipulating that “…it had to be a true navigational system…unlimited number of
users…providing global coverage…sufficiently accurate to meet military needs…” (Ref. 8). This
project eventually became Air Force Project 621B established in 1963, which continued to
evolve the concept. A key systems engineering report, in annotated briefing form, was
constructed in 1963-1964 and is included in Appendix 5. This report summarizes the early GPS
concept for the orbits and the signal structure. The trade studies conducted by Aerospace at the
time showed a concept that provided a high-dynamic capability using two pseudorandom noise
signals would allow use by high-performance aircraft, as well as all the other vehicles requiring
navigation information. The signal could be detected by users at levels less than 1/100th of
ambient noise. This was accomplished using the spread spectrum concept, which was in its
infancy at the time. This technique rejected noise and, thereby, had some inherent anti-jam
capability. The concept relied on continuous measurement from the ground for signal
synchronization and included a system of “…four separate satellite constellations, each served
by an independent ground-control station, at least two of which would have to be located outside
of the United States, (and) was not acceptable from a survivability standpoint” (Ref. 24). Time
was transmitted from the ground to the satellites. The project successfully demonstrated satellite
ranging based upon pseudorandom noise signals. Testing was conducted at Holloman
AFB/White Sands Missile Range (WSMR) in early 1972 using simulated transmitters on the
desert floor and in balloons. Aircraft accuracy was demonstrated to be less than 5 m for position
and less than 0.3 m/sec for velocity. During this time, signal definition studies were being
conducted with Magnavox Research Lab and Philco-Ford Corp. Magnavox Hazeltine and
Aerospace Corporation provided significant efforts that led to the jam-resistant passive ranging
signal (CDMA Spread spectrum–Pseudo-random noise) [17, Parkinson].
22
Roger Easton, Navy Research Laboratory (NRL), “formulated a concept in April 1964
for transmitted ranging signals along with primary CW signal, such that the distance to the target
satellite could be passively measured…” (Ref. 23). This concept led to the initiation of the
Navy’s TIMATION program and “…under the direction of Roger Easton, (the project) concen-
trated on developing an improved quartz frequency standard for satellites and determining the
most effective satellite constellation for providing worldwide coverage” (Ref. 23). The concept
proposed was to advance the development of high-stability clocks, time transfer capability and
three-dimensional navigation, and to determine the most effective satellite configuration for
global coverage. Side-tone range signals were transmitted from the satellite and space-borne
clocks would be updated by a master clock on the ground. TIMATION utilized clocks on-board
the satellite that were derived from stable crystal oscillators (Ref. 23). The baseline signal struc-
ture would require different frequencies when multiple satellites were transmitting. The two
TIMATION satellites launched under this program were at a 500 nautical mile polar orbit. These
initial satellites validated the feasibility of time transfer from the satellite at several worldwide
locations.
In order to minimize updates required to space-borne atomic clocks, NRL pursued a
change to the international time standard. “Since the satellite navigation was going to be an
expected major and critical user of Precise Time, the NRL (Roger Easton)…urged USNO (Dr.
Winkler) to work for a change in the timekeeping adjustment procedures. This was
accomplished due in part to several other initiatives including Dr Winkler’s…with adoption of
the new Coordinated Universal Time (UTC) system by the responsible coordinating international
bodies, the CCIR (Comité Consultatif International des Radio Communications), the ITU
(International Telecommunications Union), the IAU (International Astronomical Union), and the
CIPM (International Conference for Weights and Measures)… effective 1970. The new UTC
system with very infrequent leap seconds and a fixed frequency avoided (important particularly
for space applications) the small frequency adjustments used then to keep the Atomic clock time
(UTC) in close agreement (<0.9s) with earth time (UT1)” (Ref. 34).
Deputy Secretary Packard2issued DoD Directive 5160.51 on 31 August 1971, re-
emphasizing the designation of the USNO as the responsible agency for ensuring “uniformity in
precise time and time interval operations including measurements…” and “…for establishment
of overall DoD requirements for time and time interval” (Ref. 24).
The Army was also interested in satellite navigation systems. “The U.S. Army developed
the SECOR (Sequential Collation of Range) system and the first SECOR transponder was orbited
on ANNA-1B in 1962. The SECOR system continued in use through 1970. The system
operated on the principle that an electromagnetic wave propagated through space undergoes a
phase shift proportional to the distance traveled. A ground station transmitted a phase-modulated
signal, which was received by the satellite-borne transponder and returned to the ground. The
phase shift experienced by the signal during the round trip from ground to satellite and back to
ground was measured electronically at the ground station, which provided as its output a
digitized representation of range” (Ref. 25). Thirteen satellites were launched between 1964 and
1969.
2 Honorable David Packard was Deputy Secretary of Defense from 19
69
to 1971.
23
In 1968, the Joint Chief of Staff (JCS) directed an effort to develop concepts of a three-
dimensional, global, continuous navigational system. This effort resulted in the establishment of
the Navigation Satellite Executive Steering Group (NAVSEG) [1, Beard]. It was “…chartered to
determine the feasibility and the practicality of a space-based navigation system for improving
military navigation and positioning” (Ref. 26). NAVSEG contracted a number of studies to fine
tune the basic navigation concepts. These included choice of frequency (L-band vs. C-band), design
of signal structure, atomic clock development, and selection of satellite concept configuration.
They also managed concept debates in which ARL pushed for expanded TRANSIT, NRL for
expanded TIMATION, and the Air Force pushed for synchronous orbits with pseudorandom
noise signals (Ref. 27). The Naval Weapons Lab-Dahlgren (now the Naval Surface Weapons
Center-Dahlgren) conducted significant studies in tracking and orbit predictions. All the major
navigational studies sponsored by the NAVSEG from 1968 through 1972 were classified. The
original concept plan, which was later modified with the establishment of a joint program office,
was to have a demonstration of each proposed navigational concept being developed by the
services to evaluate their capabilities. [1, Beard].
No defined operational need among the services drove the development of a space-based
navigation system to improve air, land, or sea navigation and position accuracy, other than the
Navy’s requirement. Recall this requirement was for precise location of their nuclear submarines
used for missile launch that was being fulfilled by the TRANSIT system. The TRANSIT,
originally intended for submarines, was beginning to be used by commercial marine navigators.
Each service was individually exploring technology efforts for navigational improvements with
space-based satellite concepts.
In May 1972, the Secretary of the Air Force endorsed a draft Concept Development Paper
to the Director, Defense Research and Engineering (DDR&E). The paper described an “opera-
tional feasibility demonstration program using a constellation of repeater satellites” (Ref. 12).
Decisions had previously been made that a joint test program would be conducted using a
pseudo-random noise generator developed under Air Force funding onboard the TIMATION III
satellite to be launched in late 1973, actually launched in 1974 as Navigation Technology Satel-
lite (NTS) I.
A Program Management Directive (PMD) for a Satellite System for Precise Navigation
was issued by HQ USAF Deputy Director of Space, DCS/Research and Development on 19 July
1972. The purpose of the PMD was for Air Force Systems Command (AFSC) “…to define and
configure a satellite-based positioning system…(to) provide suitably equipped users the capability to
determine three dimensional position and velocity, and time information on a global basis” (Ref. 12).
The PMD also directed an initial demonstration of the operational feasibility of a global posi-
tioning system with the intent to verify the system technical concepts such as accuracy, availability,
signal structure, and satellite tracking. A six-year (FY73-78), $148M projected program was identi-
fied in the PMD. Magnavox Research Laboratories and Philco-Ford Corporation were already
conducting studies on signal structure candidates and TRW was investigating user equipment
receiver configurations, requirements, and costs based upon previous HQ USAF direction.
24
3.2 Establishment of a Joint Program
Deputy Secretary of Defense Packard was concerned about the proliferation of programs
being individually pursued by the services within DoD. He advocated joint efforts where similar or
parallel efforts were being addressed among the services. He took action to combine service
activities with a lead service being designated to reduce development, production, and logistics
costs. There was a proliferation of navigation systems by the individual services and the
individual weapons systems with unique navigation systems. The practically independent effort of
the three services to develop and enhance spaced-based navigation systems became an excellent
candidate for a joint program. DoD directed that the spaced-based navigation efforts by the three
services would become a joint program. The Air Force was directed to be the lead with multi-
service participation. The Joint Program Office (JPO) was to be located at the Space and Missile
System Organization (SAMSO) at Los Angeles Air Station.3
Col. Brad Parkinson was designated the program director. The JPO was manned with a
Deputy Program Managers from the Air Force, the Army, the Navy, Defense Mapping Agency,
the Marine Corps, and the Coast Guard. Col. Parkinson added a strong base of technical experts
in the appropriate functions for space, navigation systems, Kalman Filters, signal structure, signal
generation, electronics, and testing. Aerospace Corporation continued to provide valuable
technical and systems engineering analysis to the JPO as it had during Project 621B. Eventually,
there would be representatives from Strategic Air Command (SAC), NATO, and other
international organizations in the JPO.
Soon after the establishment of the JPO, the first major task was to obtain approval for the
program. The JPO structured a program that closely resembled the Air Force 621B system. This
program was presented to the Defense System Acquisition and Review Council (DSARC) in late
August 1973 to gain approval to proceed into the concept/validation phase. “Dr. Malcolm Currie,
then head of DDR&E4, expressed strong support for the idea of a new satellite-based navigation
system, but requested that the concept be broadened to embrace the views and requirements of
all services” (Ref. 12). DoD viewed the viability of the program based upon two overriding issues:
1. Should a universal, precise positioning and navigation system be initiated? This question
reduces down to two sub-questions: Will a universal system permit a significant reduction in
the total DoD cost for positioning and navigation? Will military effectiveness be
significantly increased by a universal system?
2. What is the best program orientation and pace for achieving the desired capability?
A universal navigation system could replace a significant portion of the current and planned
navigation and positioning equipment such as LORAN, TRANSIT, VOR, OMEGA, DOPPLER,
RADAR, range instrumentation, geodetic equipment, LRPDS, and ILS Approval. The Office of
Secretary of Defense (OSD) estimated that cumulative expenditure of funds from 1973 to the
mid-1980s for operations and maintenance of these facilities ranged from $7.5 B to $12.5 B.
However, approval for the program to proceed was not obtained and the near-term task ahead
was clearly defined to develop a joint technical program.
3 This decision was most likely based upon the Air Force having been identified by DoD in the past as the lead
service in operational space systems.
4 Dr. Malcolm Currie was Director DDR&E from 1973 to 1977.
25
Col. Parkinson assembled approximately 12 JPO members at the Pentagon over the 1973
Labor Day weekend and tasked the team to develop a program that would utilize the best of all
services’ concepts and technologies. The technology up to that time frame had advanced: 1)
space system reliability through the TRANSIT program; 2) the stability of atomic clocks and
quartz crystal oscillator through NRL efforts and the TIMATION program; 3) the precise
ephemeris tracking and algorithms prediction from APL/NRL/TIMATION, Project 621B, and
the Navy Surface Weapons Center; 4) the spread spectrum signal structure primarily from
Project 621B; and 5) the large-scale integrated circuits in a general industry-wide effort.
Reliability of satellites and large-scale integrated circuits had been proven. The resultant pro-
gram was a synthesis of the best from each service’s programs. This culminated in formulating
an integrated program that assessed the viability of mixing these new and emerging technologies.
As Dr. Parkinson said, “Rarely, however, have so many seemingly unrelated technical advances
occurred almost simultaneously that would permit a complex system like GPS to become a
reality” (Ref. 22)? The revised program went through a series of briefings to key decision
makers prior to reconvening the DSARC I. The DSARC I was held on 13 Dec 1973 and
approval was granted to proceed with the program into a concept development phase. The
funding line of $148M for the new program was established, allowing NRL to continue with the
TIMATION work, especially to develop and mature the atomic clock. The 621B funding line
disappeared. It is interesting to note the relative accuracy with which the Aerospace Corporation
study assessed cost for similar types of technology implementation. Chart No.
75
in Appendix 5
shows a $111M prediction in FY64 dollars for the early concept, compared with $148M in 1973
for the integrated service approach.
At this time, there was neither operating command support nor any operational mission
need nor Concept of Operations, and no advocacy for this effort. Additionally, there was some
negative feedback from operational commands that preferred funding to be spent on weapon
systems [17, Parkinson; 11, Green]. DoD began taking on the role of customer/user. They were
also becoming the advocates for the program – especially the Director of DDR&E, Dr. Malcolm
Currie – and were shaping the approach to the effort, including approval and control of
performance requirements, and ensuring that the services were providing support in terms of
funding [5, Currie].
The expected performance of the GPS was delineated in the approved Concept Devel-
opment Plan signed by the Deputy Secretary of Defense, 11 May 1974, as shown in Table 3-2.
Table 3-2. Expected GPS Performance (Ref. 13)
Characteristic Performance
Accuracy (relative and repeatable) 5-20m (1 sigma)
Accuracy (predictable) 15-30m (1 sigma)
Dimensions 3-D + time, 3-D velocity
Time to acquire a fix Real Time (for stated accuracies)
Fix Availability Continuous
Coverage Global
In addition to this performance, the system was to have the following additional charac-
teristics (Ref. 13):
26
1. Passive operations for all users
2. Be deniable to enemy
3. No saturation limit
4. Resistance to countermeasures, nuclear radiation and natural phenomenon
5. Common coordinate reference
6. Available for common use by all services and allies
7. Accuracy not degraded by changes in user altitudes
The program consisted of a three-phase approach:
Phase I – Concept/Validation
Phase II – Full-Scale Engineering Development
Phase III – Production
The program estimated a limited Initial Operational Capability (IOC) could be obtained
in 19
81
and a Full Operational Capability (FOC) in 1984. The program was baselined against
those scheduled events.
The completion of each phase would require DSARC approval before proceeding into the
next phase, which was typical of all major DoD programs. The overall program planned initial
schedule is in shown Figure 3-1. The basic tenet of this schedule, the three-phase approach, re-
mained constant through the program. The specifics would change due to funding issues, tech-
nical issues, and other extraneous events that would impact the program. These specific issues
will be addressed throughout this report.
Figure 3-1. Program Schedule (Ref. 13)5
5 The “2×2”, “3×3”, and “3×8” are the planned constellation configurations where the first number is the number of
planes and the second number is the number of SVs per plane. Only two of the three NTS SVs would be launched
in the first phase of the program.
27
The unique needs of the program efforts and the systems engineering process varied
during the three phases. In all phases, the JPO provided the leadership and focus of the effort
and maintained the overall control and management of the systems requirements. The contractor
teams and government team worked in close collaboration and mutual support to achieve the
initial vision of “five bombs in the same hole” at a reasonable cost.
3.3 Concept/Validation Phase (Phase I)
3.3.1 Objectives
The objectives of the concept/validation phase were to prove the validity of integrating
the selected technologies, define system-level requirements and architecture, initiate user equip-
ment development, and demonstrate operational utility. The tenets of the systems engineering
process would play a key role meeting the specific two objectives.
The first objective was to determine preferred UE designs and validate life cycle cost models in
the design-to-cost process. Six classes of UE were to be considered (Table 3.3). The guidance
on the UE design was to incorporate a high degree of commonality among the classes through
the use of modular designs. Sufficient quantities of UE models were to be procured to support a
comprehensive Developmental Test and Evaluation (DT&E) (Ref. 13).
Table 3-3. Proposed Classes of User Equipment (Ref. 13)
A B C D E F
High Accuracy**
High dynamics of
user
High immunity to
jamming
Medium accuracy*
High dynamic of
user
Medium immunity
to jamming
Medium Accuracy
Medium dynamics
of user
Immunity to
unintentional EMI
Low Cost
High Accuracy
Low dynamics of
user
High immunity to
jamming
High Accuracy
Low dynamics of
user
High immunity to
jamming
Medium accuracy
Low dynamics
of user
Medium immunity
to jamming
CANDIDATE MISSIONS
AIR FORCE
Strategic aircraft
Photo
Reconnaissance
ARMY
Helicopter
USMC
Close air support
Helicopter
NAVY
Close air support
Attack aircraft
AIR FORCE
Interdiction
Close air support
ARMY
Mission support
NAVY
Mission support
Surface vehicles
ASW aircraft
AIR FORCE
Airlift
Search & Rescue
Mission support
ARMY
Wheeled and track
vehicle
NAVY
Mine warfare
ARMY
Man backpack
USMC
Man backpack
NAVY
Submarine
Note: The above classes of User Equipment and Candidate missions will be refined during Phase I
** High accuracy better than 50 ft
* Medium accuracy 50-500 ft
+ Acceptable accuracy as determined by cost tradeoffs
28
The second objective was to conduct limited demonstrations of operational utility. These
demonstrations were to focus on coordinated bombing, terminal navigation, landing
approaches, airborne refueling, Army land operations, special operational techniques for anti-
jamming margins, and system vulnerability. This objective would also investigate satellite
hardening, long-term stability of rubidium frequency standards, and provide navigation signals
compatible between technology and development satellites. Experiments would continue to
space qualify advanced frequency standards. Lastly, a prototype ground station would be
developed and tested.
3.3.2 Requirements
Some basic requirements were identified in the Concept Development Paper (Ref 13).
There was no Concept of Operations (CONOPS) or defined military need for this space-based
navigation system. Col. Parkinson believed that the JPO would be responsible for developing
initial CONOPS and military utilization through the technology and operational demonstration
and development effort. He established a vision of two “key performance requirements” for this
phase. The first was the capability to demonstrate “drop five bombs in the same hole.” This
“key parameter” embodied the integration of receivers on platforms and the capability to
transmit precise space-based navigation and timing data. A demonstration would provide hard
data to gain support for the military utility of the system. Accordingly, he needed to have the
appropriate operational people observe the demonstration and review the data in order to gain
their acknowledgement of the improved capability [17, Parkinson].
The second “key parameter” in his vision was the ability to build a receiver for less than
$10,000. This complemented the first key parameter in demonstrating the affordability of this
navigational improvement.
The Government foresaw the need to have the civilian community participate in the pro-
gram. The civilian community had resources to insert new technology and drive down the costs
in their competitive environment to the benefit of DoD and the JPO [25, Scheerer]. At this time,
no one foresaw how far the civilian community usage of the “in-the-clear” GPS capability would
drive down the military cost of the user equipment – down to the $1000-$1500 range for some
units. Some commercial GPS receivers can now be purchased for less than $
100
[8, Fruehauf].
One additional benefit of civilian community involvement was the political support provided to
keep the program going [25, Scheerer].
In the early phases of GPS, the program is better viewed as a monolithic system with the
JPO controlling all parts: space, ground, and user. As the program progresses, control
dissipates. Commercial providers of the user equipment interject a strong influence. This
diffusion of control becomes more evident as the Federal Aviation Administration (FAA), Coast
Guard, and eventually the Galileo European Global Navigation System started providing
independent signaling elements. The JPO’s ability and means to effectively conduct systems
engineering dramatically changed as their control diffused. As is typical in a SoS environment,
the JPO’s role becomes more as an integrator/collaborator than a developer.
An important feature of systems engineering was the JPO view of top-level requirements.
Requirements were “negotiable”, i.e. tradable, which was a significant benefit that allowed the
29
evolution and development of the program as knowledge and technology advanced with time.
The philosophy was to understand the risk to change versus the risk to stay on the same course.
The corollary to this premise was to maximize the number of negotiable requirements. Finally, it
was important to communicate requirements to customers (operational users and DoD). This
program’s systems engineering philosophy would allow appropriate trades to be conducted to
optimize the military utility/operational concept, cost, schedule, risk, and performance/design, as
well as gain necessary support of the user.
The Phase I System Specification defined the system error budget, the system-level
functional flow diagram and interfaces, constellation support in terms of control segment, upload
station performance characteristics, the classes of user equipment, the signal structure to be used,
and the required software standard. Since the GPS was “a system of systems”6 not connected by
hardware, other system-level physical characteristic requirements – such as reliability and
maintainability, design and construction, human factors, logistics, as well as personnel and
training, were deferred to the system segment specifications. There was no system verification
section. For this phase, a fourth segment or element of the system was defined as the navigation
technology segment to address the NTS, the NRL telemetry, tracking and control segment, and
the PRN navigation assembly. Figure 3-2 defines the Phase I system interfaces.
Figure 3-2. System Interfaces (Ref. 28)
The development of the SV performance requirements was a rigorous joint development
effort with the JPO and the bidders prior to the Request for Proposal (RFP) being released. “The
Air Force…clearly spelled out the requirements for the satellite. The requirements did not change
during the Phase I program which allowed the team to build and test hardware and not constantly
change it,” said Dick Schwartz, Rockwell Block I Program Manager. Rockwell took the detailed
6 There are various definitions of “System of Systems”. In this report, the authors determined that the GPS was a Sys-
tem of Systems for the following reason: There were three major system segments (SV, CS, UE) that were developed
by separate contracts and physically independent with only the interface of signals as the “string” that tied them to-
gether. Each segment was considered a system composed of various subsystems that were being developed to meet
the segment system performance. Each of the three “Systems’ combined to provide a system navigational capability.
30
requirements for each SV subsystem and wrote detailed subcontractor specifications for fixed-
price subcontractor bids. The JPO added no additional requirements to this phase of the program.
From contract award to launch in 3½ years, there were only two small configuration changes to
the satellite. The main focus was on building the configuration that was developed in the year
before the contract award [26, Schwartz].
3.3.3 Acquisition Strategy
The JPO was organizationally set up with three major branches/groups with respect to the
segments of the system: space vehicle (SV), control segment (CS), and user equipment (UE).
The systems engineering group owned the system-level configuration and interface control
processes. Col. Parkinson determined that the JPO would be responsible for system integration
to the initial concern of Aerospace Corporation and contractors. Managing the interfaces and
retaining control of the system specification was an essential and critically important strategy for
Col. Parkinson and the JPO. He believed that, “Unless I was at the center of the systems
engineering involved here, I didn’t think I could pull it off either, because the contractors quickly
close you out of the essential decisions here. Making the trades would be left to them on what-
ever motivation they had” (Ref. 21). He had difficulty convincing his own management, Gen.
Schultz at Space and Missile Systems Office (SAMSO), which eventually became
Space
Division. Finally, he convinced him that the system was defined by signal structure in space and
not by physical interfaces [17, Parkinson].
The acquisition strategy was to issue separate contracts for each segment. The Develop-
ment Concept Paper scoped the approach to contracting: “Since the vast majority of the technol-
ogy for GPS is well in hand, fixed price multiple incentive contracts will be used where possible”
(Ref. 13). However, the initial UE development would be cost-plus-incentive fee contracts due
to the risk in the development of a low-cost, lightweight receiver.
The basic costing tenet from the services was that the Army and Navy funded unique UE
and service-peculiar testing, the Navy funded NTS and testing, and the Air Force funded NDS,
testing, and Air Force UE. The Air Force funded the CS and SV segments efforts.
There were six principal contractors for this phase which are shown in Table 3-4:
Table 3-4. Phase I Major Contractors (Ref. 4)
Contractor Responsibility
Rockwell International (RI) Development satellites
General Dynamics Control segment and direction to Magnavox
Magnavox User Equipment
Texas Instrument (TI) User Equipment (alternate source)
Stanford Telecommunications Inc. Signal Structure
Rockwell Collins (actually under contract
to Air Force Avionics Laboratory)
User Equipment (General Development Model (GDM)
sponsored by the Air Force Avionics Lab. GDM also
used to evaluate anti-jam system techniques)
Rockwell International, Seal Beach CA, was awarded a fixed-price incentive fee with an
Award Fee contract in Jun 1974 for four Block I satellites, one of which was the refurbished quali-
31
fication model. The contract (F04701-C-74-0527) was modified and additional satellites were
purchased for a total of eight satellites (see paragraph 3.3.7 for additional insight as to the need
for the additional satellites). In 1979, four replenishment satellites would be purchased under a
separate contract (F04701-C-79-0153). The last Block I satellite (SV) was converted to a Block
II qualification test vehicle under an engineering change proposal [21, Reaser].
In September 1974, the JPO awarded General Dynamics a contract to supply UE
receivers and develop the prototype ground control system. Additionally, this cost-plus-incentive
fee (CPIF) contract was to supply 40 models of seven different classes of receivers: bombers,
helicopters/fighters, transport aircraft, tanks/ships, manpack, submarines, and missiles.
Magnavox was the major subcontractor for the user equipment. Litton Industries Mellonics, and
Litton G&C Systems Division were major subcontractors providing supporting software for the
ground control segment and instrument test equipment. Texas Instruments was awarded a fixed-
price contract for development of a manpack receiver, computer equipment, and a pair of high-
performance aircraft receivers. Rockwell Collins was on contract to the Air Force Avionics
Laboratory to evaluate space-based navigational signals and the concept of high anti-jam
receivers via a General Development Model (GDM), shown in Figure 3-3.
Figure 3-3. Rockwell Collins GDM (Ref. 47)
The DoD, realizing the strong potential for commercial application and foreseeing the
benefits of more competition, announced that those who developed receivers with their own funds
could have their system evaluated and certified by the JPO.
The contractors accomplished some unique systems engineering approaches. “As a
contractor (Rockwell International) we took those requirements and during the pre-proposal and
proposal phase…built hardware to demonstrate the critical spacecraft technologies. We were
able to include test data on real hardware in the proposal.” Rockwell built and tested hardware,
such as atomic clocks, navigation band high-power amplifiers, and antennas during the proposal
phase. “We had a complete design for the satellite backed up by test data that was submitted as
part of the proposal” [26, Schwartz].
The SV contract type was a fixed-price incentive with a 125% ceiling and an 80%/ 20%
share between the target and ceiling. The contract also included a $100K threshold change
clause (no changes under $100K) with a manpower provision for studies [11, Green]. The 125%
32
ceiling provided a margin for problem resolution and the share line provided the motivation to
minimize cost. The Award Fee program evaluated management performance. “My view was
that the AF had excellent people and suggestions because they viewed the program from an
overall perspective, and the comments were constructive” [26, Schwartz].
There were also on-orbit incentives in the SV contract. These were daily incentives for
satellite performance in orbit where the navigation signal was measured at the CS Signal struc-
ture, and strength was measured from when the satellite rose 5 degrees above the horizon until it
set 5 degrees above the horizon [26, Schwartz].
Rockwell established a dedicated project organization with personnel co-located next to
the spacecraft assembly and test area. These technical personnel were handpicked by the GPS
program manager. An engineer managed each subsystem and was responsible for the subsystem
design, the interface with other systems, management of subcontractors, overseeing the
fabrication of parts, development of test procedures, and the conduct of testing [26, Schwartz].
Aerospace Corporation provided technical experience from all of the Air Force satellite
programs. Irv Rezpnick, the Senior Aerospace manager, provided support developing the SV test
programs, subcontractor reviews, and high reliability parts program [26, Schwartz].
3.3.4 Trade Studies
General Dynamics conducted a major set of trade early in Phase I (July 1974), to provide
recommendations on several key program decisions required in this phase (Ref. 19). These trade
studies are depicted in Table 3-5.
The trade studies below considered the impact on the next phases of the program. With
respect to the orbit portion of the study, the program baseline of 4-satellite constellations was
assessed. Paragraph 3.3.7 below discusses the need for spare satellites, which drove a change to
the configuration. These studies provided preliminary allocated baselines to the control segment
and the UE during this initial phase of the program. As concept validation testing continued and
the designs matured, final baseline allocation would be established as the program moved into
the next phase. The CS consisted of three main configuration items: the master control station,
the monitoring station, and the upload station.
Table 3-5. General Dynamics Phase I Trade Studies (Ref. 19)
Trade Study Selection
Satellite Memory Loading Resolve the method for uploading user-required data and verifying accuracy after SV has received it. S-band uplink and L-band downlink, verified at SV
Satellite Orbit Resulted in a 2/2/0 configuration
Monitor Station Sites Selection: Hawaii, VAFB, Elmendorf AFB & TBD; VAFB to be MCS and Upload Station
Control Segment Computers Evaluation criteria established
User Segment Computer Interim findings only…did not consider on Phases II/III
User Cost/Performance Low fidelity study, some cost/performance data; no selection
User Ionosphere Model Identified important features: user storage, satellite transmission & technique accuracy
User Ephemeris Model Kepler functional model, functional ephemeris
Ephemeris Determination
33
In conjunction with Aerospace Corporation, the JPO conducted various analyses and trade
studies on operational constellation concepts that resulted in a baseline configuration of eight
satellites, each in three circular rings with 63-degree inclinations. Major considerations were the
global coverage, satellite replacement issues, and the location of the remote sites. Figure 3-4 was
the early planned constellation approach of constellation arrangement as the number of satellites
in orbit increased. The consensus was that a trade study should be conducted to determine a
higher SV orbit, as it would reduce the number of satellites required. However, the Atlas rocket
with stage vehicle that was developed could only support the 1000 lb SV to the 12-hour orbit. It
turned out that this orbit configuration was adequate to support the testing at Yuma Proving
Grounds (YPG) with a limited constellation [11, Green]. As the program progressed, external
events would require the JPO and Aerospace Corporation to conduct a trade analysis of the
constellation configuration and modify the functional baseline.
Figure 3-4. Planned Constellation Development before 1974. Proof of Concept has 6 Block I
satellites in 2 planes. Build up to 24 Block II satellites in 3 planes (Ref. 18)
The PRN signal structure is the key enabling technology of GPS, resulting from extensive sys-
tems engineering analysis and trade studies dating back to the early Aerospace studies sponsored
by AFSC/SMC (Appendix 5). The whole structure of the system revolved around the ability to
communicate accurate navigation and timing data to each of the segments. Extensive signal and
communications message development trade studies that bridged from Project 621B to this phase
were conducted. The Project 621B study system employed signal modulation and used a repeated
digital sequence of random bits. The sequences of bits were simple to generate by using a shift
register, or by simply storing the entire bit sequence if the code was sufficiently short. The
sensing equipment detected the start phase of the repeater sequence and used this information to
determine the range to a satellite. The concept of PRN ranging was led by Aerospace Corpo-
ration and Magnavox. Dr. Charles Cahn was a signal analyst who, with Dr. Robert Gold, was
involved in the development of the signal architecture [28, Stansell]. The first receivers
developed for PRN ranging were Magnavox Hazeltine. The signal structure was defined by Drs.
34
Nataly and Spilker. Maj. Mel Birnbaum and Dr. Van Dierendonk [17, Parkinson] led design of
the message structure and the systems engineering process.
3.3.5 Risk Mitigation
One of the key risks going into this phase was the ability to validate that the Atomic Fre-
quency Standards (AFSs), or clocks, performed in a space environment and provided precise
timing to the user equipment. The GPS concept was based upon a reliable, ultra-stable AFS.
The atomic clocks were one of the key technologies instrumental in making GPS a viable
system. This technology was developed as an offshoot of research on magnetic resonance to
measure natural frequencies of atoms that began in 1938 with Dr. Rabi at Columbia University.
The development of atomic clock technology over the years resulted in more-accurate and
smaller-packaged atomic clocks.
The atomic clocks in the GPS satellites were essential in providing GPS users accurate
position, velocity, and time determinations. They provided a precise standard time – the fourth
parameter. In addition to the three-dimensional coordinates of the SV, this allowed the user to
receive sets of four parameters from four satellites and solve the equations establishing a four-
dimensional location of the receiver (three spatial dimensions plus time). The clocks became
one of the key development items for the program.
As the GPS program was being established, plans were already in place to conduct test-
ing using the Navy TIMATION satellites with atomic clocks onboard and incorporating Project
621B code generators. The objectives of the NTS concept development tests were to validate the
behavior of accurate space-based clocks, the techniques for high-resolution satellite orbit predic-
tion, the dissemination of precise time data worldwide, and the signal propagation characteristics.
NRL led the contracting and supply of the NTS atomic clocks. Two commercial rubidium Rb
clocks purchased from Efratom Munich and a quartz crystal oscillator were flown on NTS-1.
The Rb clocks were modified by NRL for flight experiments to reduce expected thermal problems
in space. The NTS-1 had attitude determination problems that caused wide temperature swings,
which caused frequency swings in the clock and failure after about one year. Necessary
performance validation data were obtained before the failures. The Rb clocks were not space-
qualified.
Rockwell developed a PRN code generator and space-borne GPS computer that were
incorporated into NTS-2. Two more-robust, space-qualified Cesium atomic clocks built by
Frequency and Time System (FTS – now Symmetricom) were launched on NTS-2 [30, White].
The NTS effort was managed through a fourth segment of the GP system – the navigation-
technology segment – and focused on validating various technology concepts, especially the
space-borne atomic clocks. “The navigation-technology segment of the GPS provided initial
space-qualification tests of rubidium and cesium clocks. This segment also provided the original
test of the GPS signals from space, certification of the relativity theory, measurement of radiation
effects, longevity effects on solar cells, and initial orbital calculations…Precise time synchroni-
zation of remote worldwide ground clocks was obtained using both NTS-1 and NTS-2 satellites.
(During) May through September 1978 with a six-nation cooperative experiment,… (tests were)
performed to inter-compare time standards of major laboratories” (Ref. 1). The NTS SVs per-
35
formed adequately for the prototype objectives intended and provided sufficient data to proceed
with the further development of improved atomic clocks. NTS command and telemetry links for
these tests came from many of the Navy ground systems during the TIMATION program.
NTS/TIMATION SV tracking and control was accomplished at NRL’s Blossom Point, MD
satellite control facility. NRL operated several NTS/TIMATION monitor sites to collect and
characterize the navigational signal. Elements and functions of the NTS-2 system, including
ground stations, are shown in Figure 3-5. An NTS SV is shown in Figure 3-6.
Figure 3-5. NTS-2 Command and Telemetry Links (Ref. 1)
Figure 3-6. NTS-2 Satellite (Ref. 23)
36
The other key risk addressed in this phase was the ability to validate the prototype
receivers being developed could precisely predict location using the navigational and time
signals being generated. The primary objective of this phase was to establish performance limits
of the UE under dynamic conditions in a severe environment. As Col. Parkinson stated, it was
“…a classical bureaucratic ‘Catch 22’: How could user equipment development be approved
when it wasn’t clear it would work with the satellites? How could the satellites be launched
without ensuring they would work with the user equipment?” (Ref. 18). Relying on experience
from the Project 621WSMR test program, the JPO devised a plan to use an array of four
surveyed ground-based transmitters (called pseudolites, derived from pseudo-satellites), which
would generate and transmit the satellite signal. The test program would be conducted with the
prototype and initial developmental UE to validate the signal compatibility with the receivers.
Azimuth and angular errors were a challenge that had to be considered in the test planning and
execution. The fidelity of the ground-based system would be enhanced as the Block I satellites
began to be launched. Pseudolites were used in conjunction with launched satellites until a
minimum of four satellites were available in orbit. The (YPG) was selected as the test site in lieu
of WSMR as a result of a trade study. This approach had the benefit of enhancing the Army
involvement as a stakeholder in the program. Magnavox Advanced Product Division was re-
sponsible for the development and fabrication of the pseudolites and a control station at the test site.
During the initial phases of testing, problems were encountered when the receiver display
would indicate an “anti-jam” threat due to the power levels being transmitted by the pseudolites.
A design and procedure change eliminated the deficiency [11, Green]. This test program was the
first to use a triple-triangulated laser to conduct precise measurements of aircraft location to verify
user location (aircraft) [16, Parkinson]. “The laser tracking system provided an accuracy of
about one meter. To simulate the much longer real distance between user equipment and the SV,
an extra code offset was used” (Ref. 16). Testing was conducted at YPG from March 19
77
to
May 1979. Demonstrations began with user equipment installed on a C-141 cargo transport, F-
4J fighter, HH-1 helicopter, and Navy P-3 aircraft. Testing proceeded with manpack and other
user host vehicles. Some of the YPG test results with respect to the blind bombing tests with the
F-4J and X-set receivers, F-4J and C-141 rendezvous test and the manpack tests are shown in
Figure 3-7. As the testing progressed and three satellites were in orbit, on-board ship user
equipment was tested off the California coast. Eventually during this phase, over
77
5 mission tests
were conducted with various classes of test vehicles.
37
Figure 3-7. Phase 1 YPG Test Results (Ref. 51)
Air Force Test and Evaluation Command (AFTEC, later to become AFOTEC) conducted
an independent evaluation and found no significant operational issues with the operational demon-
stration tests [17, Parkinson].
3.3.6 System Integration
The JPO decided to retain core systems engineering/system integration responsibility.
Col. Parkinson had a concern with the potential for proliferation of systems engineering groups
within an organization. He viewed systems engineering as a common-sense approach to creating
an atmosphere to synthesize solutions based upon a requirements process, and to ensure good
validation/verification of the design to meet those requirements7. He advocated using good
systems engineering principles to work issues as they arose [17, Parkinson].
The “major cornerstone of the program” from a program execution and system integra-
tion perspective were the interface controls. It was vital not only to this phase, but to the entire
program, that a strong systems engineering process be established. This ensured that technical
inputs and requirements, verification, conditions, and CONOPS of all the government, contractor
agencies, and international communities were considered in a timely manner, and a means of
communication among those agencies was established.
7 Col. Parkinson did not mention though implied within reasonable cost and schedule.
38
The integration role required contact with many government and industry entities. A
plethora of technical expertise organizations, test organizations, users, etc. required working
interfaces and integration. Figure 3-8 provides a view of the program interfaces required with
other agencies/contractors and indicates the complexity of the interfaces required.
Figure 3-8. GPS JPO Agency/Contractor Interfaces
In this phase, a significant amount of fluidity among the design concept and agencies
involved further underscored the need for unimpeded communications. The program set up an
acquisition strategy that created separate contractual efforts for the three major segments: Space
Vehicle (SV), Control Segment (CS), and User Equipment (UE). A unique fall-out of this
delineation was no physical connection between the segments. All the segment interfaces within
the system were related to the transmitted signals. The system specification and the Type I
Interface Control Documents (ICDs) were written and controlled by the JPO. The system
specification was not contractually binding on any of the segment contracts. The segment
specifications and their companion ICDs written by the contractors were assessed by the JPO
System Group for compliance with the system specification. These specifications and the ICD
were generally written in cooperation with the JPO. Interfaces in the CS segment specifications
were sometimes “soft” with respect to interfaces with other GPS segments and systems. The
segment specifications were placed on contract for each of the segment contractors. This
situation emphasized the need for a robust interface control process.
39
Figure 3-9 is the top-level specification tree for Block I, which includes the unique Block
I navigational technology system segment. Figure 3-10 is a Block II/IIA flow chart, but provides
a good indication of the interfaces for the major system segments. The JPO Systems
Engineering Directorate was responsible for configuration management and accomplished the
administrative duties and coordination for the Configuration Control Board chaired by the
Program Director.
Figure 3-9. Phase I Specification Tree (Ref. 28)
Figure 3-10. Phase II Specification Tree (Ref. 41)
In 1975, the JPO developed and approved the Interface Control Working Group (ICWG)
Charter that outlined the program interface process. This document was signed by the service
representative and the major segment contractors. The JPO had approval control over ICDs and
would chair/co-chair all ICWG meetings. A contractor was identified as the Interface Control
Coordinator (ICC) with administrative responsibilities in addition to the technical responsibilities
for their area. This approach was consistent with the JPO being the system integrator. Again,
this was an initial concern to Aerospace Corporation, who expected to have more of a system
integration role in the program and with the contractors [17, Parkinson].
40
The charter described three levels of ICDs:
Type I – Interface with agencies outside the JPO; i.e. system-to-system
Type II – Interfaces between the major segments of the system; e.g. SV -UE
Type III – Interfaces within the system segments; e.g. CS CI “A” to CS CI “B”
The Charter also established a hierarchy to the interface decision process with the Interface
Control Steering Group overseeing the Interface Management Group, who oversaw the ICWG to
ensure a structured means of program issue resolution.
The JPO Systems Engineering Directorate was responsible for configuration management
of specifications, Level I ICDs, and system design configurations. The directorate accomplished
the administrative duties and coordination for the Configuration Control Board, chaired by the
Program Director.
Maj. Mel Birnbaum from the Systems Engineering Directorate was the focal point within
the JPO for the ICWG process during the early phases of the program. He was credited by his
peers at the JPO and on the contractor side as the key individual to making the system integration
work during Phases I and II [25, Scheerer; 21, Reaser ; 8, Fruehauf; 16, Nakamura; 14,
Krishnamurti; 23, Robertson]. The technical support from Aerospace Corporation to the ICWG
process also contributed to the success. Their support in a system integration support role was
methodic and added technical value, complementing the JPO effort [25, Scheerer].
The ICWG process would not have worked with the JPO and Aerospace Corporation
alone – the contractors were an integral part of the process. Although initially reluctant to being
controlled by the ICWG, each contractor became very proactive in the process. Both the JPO
and the contractor program management provided an atmosphere of mission success that fed this
support. Host vehicles (user systems) and other pertinent agencies were always well represented
and active. Typically, ICWG meetings lasted two to three days and were very grueling according
to some participants. A typical ICWG agenda would consist of a review of the contractor’s latest
design, identifying interface issues/changes, and establishing action items that were logged and
tracked. The status of the segment designs defined the next phase meeting agenda. There were
examples of the contractors recognizing an evolving issue and, without direction, working
overnight to develop a solution by the beginning of the next day’s meeting [17, Parkinson].
Though the ICWGs were well structured, there was flexibility in the process. During this phase,
Rockwell Collins had a concern about the 50 Hz data message definitions in ICD-GPS-200
between the space segment and the user equipment. They called Maj. Birnbaum, identified the
issues, and presented the logical rationale for the need for the change. Four weeks later, the ICD
had been changed without further coordination. The JPO – as the integrator – made the change
unilaterally [14, Krishnamurti].
41
The number of ICDs grew during the program. By 1979, per the ICWG Charter (YEN-
75-134), there were 19 major ICDs identified. These did not include all the Type III ICDs.
Eventually, the program managed over 200 Type I-Type III ICDs [21, Reaser]. Figure 3-11
illustrates the breadth of some of the ICDs. The ICWG process was instrumental in making the
system work as an integrated whole.
Figure 3-11. Interface Control Documents (chart from 2005 JPO SE briefing
that captures the breadth of some 200 ICDs) (Ref. 29)
Figure 3-12, GPS Functional Flow Diagram, illustrates the interfaces with other elements
of the system besides the three major segments defined in the system specification. The other
interfaces identified included the rocket, launch, range support, and data processing
(computational support).
3.3.7 Systems Engineering
Although the systems engineering process in Phase I has been discussed
previously, this section will expand on the concepts. For example, one of the user equipment
contractors was technically competent, but lacked effective management. The JPO strongly
suggested that a systems engineering firm be hired to assist the contractor in managing program
and they agreed [17, Parkinson].
In order to conduct the later phase of testing at YPG with Block I SV being in the loop, a
prototype system had to be developed. This would consist of a ground control system with up-
load and satellite control, and an optimized SVs test constellation. The General Dynamics Control/
User Segment trade study (Ref. 19) had established a preferred approach, which the JPO followed.
An interim control system (ICS) was established at Vandenberg AFB (VAFB). The four remote
sites were selected based upon three recommended by the General Dynamics study: Hawaii,
Alaska, and VAFB – Guam was selected for the fourth site. The contract with General
Dynamics and Magnavox was a fixed-price contract per direction from HQ AFSC/CC, Gen.
Alton Slay. The program at this stage was still too fluid. Hardware was state-of-the-art and did
42
not present issues. The major effort was in software for the modeling of ephemeris equations and
the atomic clocks, as well as maintaining reasonable program error margins/accuracy. Contractor-
government working relationships were strained as a result of the efforts required once on contract.
Eventually, communications improved and mutual trust was established [16, Nakamura]. There
were no typical user/operational input requirements to this phase of the control station
development. In this concept development phase, the JPO became the “user” for developing the
requirements for the support systems structure, the CS. The JPO utilized experience from the
Navy TIMATION launch and SV control systems, the WSMR ground testing, other Air Force
rocket programs, and the unique requirements of this program to develop the CS concept of
operations and the performance requirements.
Figure 3-12. GPS Functional Flow Diagram (Ref. 28)
In conjunction with this support structure effort, the Systems and Space Segment groups had
to define a constellation that would maximize the test window over YPG. The General Dynamics
study had recommended a constellation of four satellites. The baseline program had contracted
with Rockwell for four Block I satellites, one of which was to be a refurbished qualification unit.
However, the analysis did not consider the failure mode of any one satellite in orbit, which would
create coverage and accuracy issues with respect to the YPG test plan. This had not been
considered as an issue when the initial program plan was developed. It soon became apparent,
after further analysis, that the minimum satellite requirement for testing was six in order to assure
acquisition of data to meet the objectives of this phase. The program needed spare satellites to
complement the four that Rockwell was on task to supply. This situation presented a cost and
schedule risk to the demonstration testing. The requirement for four SVs was reflected in the
budget established for the program during and soon after DSARC I. It would be quite difficult to
request additional funding so soon after the baseline program was established. In the upfront
program formation, the systems engineering process had not adequately addressed the
43
reliability/availability and logistics/support requirements in conjunction with the test mission,
concept of operations, and schedule for this concept development phase.
While the JPO was trying to solve the critical dilemma of insufficient number of satellites
to conduct a reasonable test program, the Navy TRANSIT program was submitting a request for
funding to provide an upgrade to track the Trident booster. The TRANSIT plan included use of a
PRN code similar to the GPS baseline signal. The JPO saw this as an opportunity to solve their
satellite dilemma. The Systems Engineering group investigated options to provide the TRANSIT
program their enhanced capability and the JPO funding for the needed additional satellites. The
JPO proposed an approach to have the JPO be responsible for providing TRANSIT capability.
The technical solution that the GPS program developed was to accomplish the mission using a
signal translator on a missile bus relay. “Dr. Bob Cooper of DDR&E requested a series of
reviews addressing whether GPS could fulfill the (TRANSIT) mission” (Ref. 15). After a series
of reviews, Dr. Cooper concurred with the JPO proposal and transferred $60M of Navy funds to
GPS, which would allow two additional satellites to be acquired and provide TRANSIT with
their enhanced capability.
The JPO, with assistance of Aerospace Corporation, conducted analyses and trade
studies. They determined that a constellation with satellites in two circular planes would allow the
six satellites to cluster over the western CONUS once per day. This would provide three-
dimensional coverage for one to three hours at the YPG. Each satellite was uploaded daily from
the ground stations just prior to being viewed over YPG.
The two major system accuracy requirements, time and position, were allocated to vari-
ous segments via error budgets. In the Precise Positioning Service (PPS) system, range error – a
measure of the error in range to each satellite as seen by the receiver – was allocated to the three
major segments. These allocations are depicted in Table 3-6.
Table 3-6. GPS PPS System Error Range Budget (Ref. 42)*
Segment Error Source
UERE Contribution
(meters, 95%)
P-Code C/A Code
Space
Frequency standard stability 6.5 6.5
D-band delay variation 1.0 1.0
Space vehicle acceleration uncertainty 2.0 2.0
Other 1.0 1.0
Control
Ephemeris prediction and model implementation 8.2 8.2
Other 1.8 1.8
User
Ionospheric delay compensation 4.5 9.8-19.6
Tropospheric delay compensation 3.9 3.9
Receiver noise and reduction 2.9 2.9
Multipath 2.4 2.4
Other 1.0 1.0
Total (RSS) System UERE (meters, 95%) 13.0 15.7-23.1
*User Range Equivalent Error (UERE) is a measure of the error in range measurement to each satellite as
seen by the receiver. The portion allocated to the Space and Control Segments is called the User Range
Error (URE) and the portion allocated to the UE is called the UE Error (UEE). UERE is the root-sum-square
of the URE and UEE.
44
The system time transfer error budget (in nanoseconds based upon 95% probability)
allocations are depicted in Table 3-7. Each of the major system segments was responsible for
meeting their allocated error budget requirements. These time and position allocations were not
only tracked by the Segment Group, but also by the Systems Group within the JPO.
Table 3-7. GPS Time Error Budget (Ref. 42)
Error Component Error (ns, 95%)
US Naval Observatory Measurement Component 137
Control Segment Measurement Component 59
GPS Time Predictability
92
Navigation Message Quantization 6
Satellite Orbit 22
Satellite Clock 63
Satellite Group Delay 12
Downlink and User Equipment 65
Total (RSS) Time Transfer Error Budget 1
99
3.3.8 DSARC II
The programmatic culmination of Phase I was to provide evidence of meeting the objec-
tives of the phase and obtain approval from DSARC II to proceed to the next phase. Included were
full-scale engineering development, validated navigation signal compatibility, prototype ground
station, and preferred UE designs. AFTEC determined that there were no major operational
deficiencies that would prohibit continued development and testing. This phase had
demonstrated the capability of the atomic clocks to be a stable system in the space environment
and established cost estimates for the program. DSARC II was held on 5 Jun 1979. The “DSARC
has expressed concern about system cost, notwithstanding the demonstrated performance and the
significant operational benefits which will accrue by its deployment…places the DSARC
approved program alternative at the Basic level and a delayed program of reduced
scope.…thorough review to identify potential cost reductions (i.e. analysis of all requirements,
system specifications, testing contracting, etc.) but also restraint during the engineering
development phase to insure future development efforts are focused on essential modifications”
(Ref. 30). As a result of the DSCARC, the baseline IOC was revised to 1986.
3.4 System Development (Phase II, Block I)
3.4.1 Objectives
The objectives of Phase II were to develop the SVs, complete Initial operational Test and
Evaluation (IOT&E) of user equipment, initiate production of low-cost mission-support UE, and
establish a two-dimensional limited operational capability. Rockwell International had been
placed on contract for the SV development and General Dynamics was on contract for the ICS.
Block I would not require implementation of selective availability or anti-spoofing
45
requirements8. The requirement for a nuclear detection system as a secondary payload was to be
implemented. The launch vehicle for these SVs was the Atlas E/F.
3.4.2 Systems Engineering (JPO)
During this time frame, Col. Reynolds (JPO Director 1980 to 1983) determined that the
Systems Engineering Directorate should take on more of an integration role. He believed that too
many unresolved issues between the segments and/or systems were being raised to his level for
conflict resolution. He wanted the Systems Engineering Directorate to be mainly responsible for
the integration between the system segments. Their mission was changed to receive, debate, and
allocate requirements; arbitrate issues among the segments; maintain the system architecture,
which was fairly stable at this time; and continue to be responsible for the ICDs and system
specification [22, Reynolds]. They would also monitor systems engineering processes being
used by the segments. This Directorate was “…like an anti-body forcing Segments to make sure
they were doing good systems engineering. Otherwise, the Segment group feared that the Systems
Engineering Directorate would get involved in your program and possibly take over [21, Reaser].”
Col. Reynolds’ philosophy during this phase was “…don’t be elegant and don’t make everything
new, go with proven technology” [22, Reynolds].
Col. Reynolds also wanted to assure support from other communities (e.g. DMA, FAA,
USCG, and Cambridge Research Laboratory). This was a critical time in the program from a
budget standpoint, and to proactively advocate the program utility to potential customers within
DoD, international allies, and the commercial side. The Systems Engineering Directorate was
responsible for providing domain knowledge of interfaces to the potential customer’s
requirements. This was often accomplished on-site with demonstrations (with the manpack).
Col. Reynolds formed alliances with the communities that were neutral, or even
antagonistic, toward the program. The FAA was developing the microwave landing system and
GPS could be considered a threat to that program. The JPO worked with the FAA to provide
better insight into the capabilities and limitations of GPS. Cambridge Research Laboratory
favored the Inertial Navigational System (INS) and appeared antagonistic toward GPS. Col.
Reynolds hired Cambridge Research Laboratory to conduct a study of INS and GPS, resulting in
a more favorable attitude toward the program, in addition to the technical benefit of the study.
3.4.3 Interface Requirements
During the development of the Interim Control Segment (ICS), an interface issue arose
with respect to telephone communications with the remote sites. The timeframe of this issue was
soon after the split-up of Bell Systems (AT&T) in 1984, due to the court ruling with respect to
monopoly interests. The contractors and government did not foresee the problems with the small
telephone companies on the West Coast establishing unique requirements/procedures that impacted
the effort to try and establish communications links among the remote stations, master control,
and the test facility. Communications routes along the West Coast and over to YPG required
extensive workarounds and time-consuming solutions [20, Prouty].
8 Selective availability is the intentional degradation of the transmitted signal by a time-varying bias on the C/A code.
Anti-spoofing guards against fake transmissions by encrypting the P-code to form the Y-code.
46
3.4.4 Budgetary Impacts to Functional Baseline
Funding became a major issue for the program in the late 1970s and early 1980s. The Air
Force, in general, was not supportive of the budget requests from the JPO. The DSARC II had
recommended the continuance of the program at a reduced scope, as mentioned in Paragraph
3.3.8. Systems engineering would play a key role in reassessing the functional baseline. There
had been a 10% reduction ($500M) in program funding. The program was restructured, resulting
in a reduction in the number of Block II SVs and a change in some performance requirements,
such as weight and power.
Senior Air Force staff questioned the ability of the system to survive threats and re-
quested that a study be conducted to identify those threats, threat countermeasures, and the cost of
those countermeasures. The Defense Intelligence Agency had no defined threat against the GPS.
The task was passed down to the Air Force and AFSC intelligence agencies before the JPO was
finally tasked and accepted to identify and assess potential threats. Systems engineering had been
continuously assessing threats to the system during the development effort. There was a
classified appendix to the system specification that detailed a threat environment that the JPO
had postulated, as there had not been any “official” defined threat. The UE contractors had to
meet this requirement, which was a tough set of requirements with respect to ground and
airborne jammers [25, Scheerer]. There was no consensus within the Air Force as to the threat
requirement and there was a genuine concern about the ability to jam the receiver. Eventually, an
“exaggerated” baseline threat scenario was established for the user equipment by which the foe
had a powerful jammer (100 KW) on 80-foot-high towers near the Forward Edge of the Battle
Area (FEBA) [25, Scheerer; 22, Reynolds]. The JPO set up and conducted testing to simulate
this condition based upon many assumptions and the scenario was successfully demonstrated.
However, there still was reluctance to fund the program. There was also a request to estimate the
cost of nuclear hardening the SV. The JPO estimated $850M for the development and production
costs [22, Reynolds].
From 1980 through 1982, funding for the program was essentially zeroed out by the Air
Force, which recommended cancellation of the program. The AF budget proposed sufficient
funds to maintain operation of six Block I satellites to enable the Navy to continue data gathering
and characterization of the Fleet Ballistic Missile (FBM) Improved Accuracy Program (IAP).
There were indicators within the JPO at the Control Segment Critical Design Review (CDR) and
at a major navigational symposium that the program was to be cancelled. Senate staffers asked
the JPO for cost estimates to shut down the program , even though they had not thought about
the cost to go to other alternatives. It appeared Air Staff would not support the program. The JPO
fostered dependencies such as embedding GPS navigation into the platforms mission – such as
the F-16 aircraft program and the Joint Tactical Information Distribution System (JTIDS) – that
would stimulate funding. After a briefing by Col. Reynolds, Secretary of Defense Harold Brown9
observed the global military need, the vested alliances established by the JPO, and future
potential users. He reinstated the funding, including the estimated funding for nuclear hardening.
Again, DoD acted in the user capacity and was influential in saving the program. Even with the
change in Presidential administrations, Secretary of Defense Casper Weinberger10 would
eventually continue to support the program [22, Reynolds].
9 Honorable Harold Brown was Secretary of Defense from 21 Jan 1977 to 20 Jan 1981
10 Honorable Casper Weinberger was Secretary of Defense from 21 Jan 1981 to 23 Nov 8
47
As a result of these budgetary exercises and funding cuts, one of the major program
impacts was to the system architecture. The number of Block II satellites had to be reduced from
21 to 18. The JPO needed to determine the impact on global coverage, and what would be the
optimal SV configuration. Through the systems engineering process, SV constellation trade studies
to determine the minimum number of satellites were conducted primarily by the JPO and
Aerospace Corporation with inputs from Rockwell. The conclusion was an 18-satellite
constellation to provide continuous global coverage to primary areas of interest. After extensive
analysis, a 6-plane constellation with equal spacing within the plane and a 55-degree inclination
(limited by launch vehicle constraints) was selected. Note that the breakpoint between a 3-plane
and 6-plane constellation was 21 SVs. Below 21 SVs, the 6-plane was more advantageous. The
implementation of the presidential directive to launch all Air Force satellites from the space
shuttle (see Paragraph 3.5.4 for more detail) was an influencing factor in the selection of the
inclination. Since the SVs had to be man-rated with respect to the Space Shuttle, the launch site
was moved from VAFB to Cape Canaveral. Launching from Cape Canaveral could not support a
63-degree inclination and had to be reduced to a 55-degree inclination [25, Scheerer]. The three
spares would be inserted into every other plane, for a total of 21 satellites. The outage of any SV
could disrupt the service over one or more critical areas of the globe with this configuration, until
the replacement satellite was deployed [22, Reynolds; 25, Scheerer; 11, Green; 21, Reaser].
The Air Force decided in the late 1970s to remove the IONDs requirement from the GPS
program and transfer it to the Defense Satellite Program (DSP). The GPS program was seeking
strategic alliances to help with funding problems in this timeframe and saw an opportunity to “re-
claim” this capability. They proposed to Gen. Jacobson at the Pentagon that, if the nuclear detection
system requirement was returned to the GPS JPO, the nuclear detection capability could have a
worldwide edge with the GPS satellites. The request was approved with the transfer of NDS inte-
gration funding and the requirement was inserted into Block II [20, Prouty]. The NDS requirement
had been changed from the initial IONDS, in that an electromagnetic pulse (EMP) sensor would
be required. The functional baseline was again adjusted to accommodate this new requirement.
3.4.5 Rockwell International Systems Engineering
The Rockwell International GPS Satellite Program Manager organized his workforce to
parallel the JPO organization so that there would be a counterpart in Rockwell for each JPO
responsibility. He believed that communications were extremely important and that there was a
need to know who to contact (both government and contractor) when there was an issue. Rockwell
organized their engineering staff into a classic project organization with a systems engineering
office, subsystems engineers, and Work Breakdown Structure (WBS) task team leaders reporting
directly to the chief program engineer. The Rockwell International Block I GPS Program
Organization chart is in Appendix 6. The two major ICDs were with the Control Segment and
User Equipment Segment. Internal ICDS (Type IIIs) were established, as required within the
subsystems. Requirements levied on Rockwell were top-level performance requirements such as
SV life, signal generation, error budget, and interface requirements [21, Reaser]. Design and
interface requirements drove system-level requirements in many cases, as there was no single
Using Command to establish them. Contractors conducted design studies to determine the best
way to implement decisions. Rockwell was focused on technical solutions that minimized cost
and schedule impact [8, Fruehauf].
48
When the IONDS requirements were levied on Rockwell, a separate chief engineer
became responsible for the interface of IONDS and the SV; the development of the L3 signal
peculiar to IONDS data transmission; and the establishment of the ICD and MOA with the
Department of Energy (DOE), specifically Sandia National Laboratories and Los Alamos
Laboratory.
The Rockwell GPS Block I design and development team (Appendix 6) focused on sim-
plicity of design for easy manufacturing and addressing the functionality of the high-risk compo-
nents. These high-risk items were: (a) the atomic clocks; (b) the navigation payload; (c) the RF chain/
High Power Amplifier (HPA); and (d) the antenna. These components were designed, fabricated,
and tested prior to contract award to reduce risk and to demonstrate feasibility. Throughout the de-
sign and development process, the theme for the GPS team was “build what is designed during the
proposal phase.” This enhanced the subsequent success during the relatively short factory-to-
launch-pad schedule. The successful GPS satellite design was the result of several engineering
concepts:
1. Focus on designing the satellite around the most important and environmentally sensitive
component – the clocks, with all other considerations virtually secondary.
2. Simplicity of design that made the satellite highly reliable, more producible, cost effective,
and compatible (without constraints) for launch initially from Atlas-F ICBMs. This reduc-
tion in complexity extended to launch and on-orbit operations.
3. Trade studies and subsequent sub-system designs that contributed to the GPS satellite sim-
plicity and reliability included:
a. Utilized single degree of freedom solar array drives and yawing the spacecraft for the
needed second degree of solar array freedom.
b. Selected solid-state HPAs – versus less-expensive Travel Wave Tubes (TWT) – for long
life, reduced power consumption, and elimination of high-voltage power supplies.
c. No on-board computer running the navigation-operations functions.
d. Utilized passive thermal control system especially designed to accommodate the temperature-
sensitive clocks, again reducing power consumption.
e. Optimized spread spectrum ranging and data-stream signal structure to meet link require-
ments, while at the same time adhering to the constraints of the national and international
regulations concerning electromagnetic radiation (Note: The GPS receiving signal power
was approximately 1×10-16 watts – practically undetectable – and, therefore, would not
require licensing in foreign countries).
f. In response to a joint JPO and Rockwell concern about how to maximize coverage of a
single SV broadcast, developed the 12-helix phased array antenna (Al Love of Rockwell
International invented the unique antenna), shifting the usual excess radiated signal power
at the bore site to the 5-degree elevation angle. This reduced power consumption and
provided a more homogeneous radiation pattern to the earth’s surface from the SVs’ line of
sight.
g. Incorporated magnetic momentum dumping11 of the active control system (ACS) reaction
wheels for longer spacecraft orbital life.
11 Magnetic Momentum Dumping (MMD) was developed for the program by the Astronautic Department at the US
Air Force Academy and first tried on Block I as an experiment. After the technology was proven, it was baselined
into the Block I Replenishment SVs and the Block II SVs [21 Reaser]. MMD is the capability to generate sufficient
49
The above efforts contributed to the reduction of solar panel surface area and to control the
weight allocated requirement.
For the GPS Block I build phase, among the many systems engineering management
concepts that contributed to cost and schedule efficiencies, was the purposeful violation of the
common taboo: “a prime contractor is advised not to be in series with the contract performance
of the subcontractors.” On the contrary, Rockwell placed itself in series in two areas: radiation
hardening design and the high-reliability space parts program.
The radiation-hardening requirement was a new technical challenge for most subcontractors.
Rockwell offered the subcontractors “zero-risk” radiation hardening design and technical expertise
via a 40-hour subcontractor bid of interface time with Dr. Norman Rudy from Rockwell’s Ballistic
Missile Division. Dr. Rudy reviewed designs in-progress, often on-site, and necessary changes
were accomplished up-front, thus reducing risk of meeting the radiation requirements. Often this
was accomplished in unique innovative system approaches. Beside minor box redesigns and use
of parts, they included needed circuit changes/additions, local parts or box shielding, and shadow
shielding from other hardware at the spacecraft level. One or more of these techniques was
applied, with Rockwell accepting the subcontractor’s product as compliant.
The high-reliability, space-qualified, S-Level (or S-equivalent) parts program was another
risk-free venture for the subcontractors on a voluntary basis. All but one of almost a dozen sub-
contractors participated in the parts pool. A qualified space parts list (QPL) was generated, with
subcontractors adding unique parts that required qualification. Total-requirement part lots were
purchased by Rockwell and S-equivalent screened when needed, qualified, and made available
for subcontractor draw-down. Using a NASA-qualified central screening house became a source
of huge cost and schedule savings. Beyond the programmatic advantages, spacecraft reliability
was achieved through large and common (non-fragmented) lot date codes: traceable, predictable
performance, and consistent test and screening procedures [8, Fruehauf].
Rockwell, as the SV segment developer, was the lead on the system development of the
signal with coordination with the UE segment. The only systems engineering decision driven by
the UE was the number of SVs that would be above the horizon (three or four) in order to keep
the cost of the UE low (Section 3.4.8 provides additional information).
SV weight was an identified upfront concern – only a 50 pound margin was allowed.
Tracking was by Technical Performance Measures (TPMs) and status was reviewed weekly by
the RI Chief Engineer.
RI tailored the general military specifications imposed on the GPS contract before pass-
ing requirements onto the subcontractors. These tailored requirements were then incorporated into
a specific boilerplate section of all the subcontractor specifications. RI engineering managers were
in daily or weekly contact with their subcontractors with frequent visits. The JPO and Aerospace
had people assigned to each subsystem who, as part of this mini-team with RI, evaluated all
torque through magnets to dump excess momentum from on-board reaction wheels without disturbing the precise
ephemeris of the SV.
50
aspects of the subcontractor. Formal subcontractor management reviews were conducted by RI
every 3-4 months with Capt. Green (JPO SV Manager), Irv Rezpnick (Senior Aerospace Manager),
and other supporting personnel accompanying Mr. Schwartz. Review out-briefs were made to the
subcontractor head at the facility on the results of the visit [26, Schwartz].
Box-level qualification and acceptance testing were accomplished according with MIL-
STD-1540. The program was one of the first to use this specification to detail requirements for
functional, shock, vibration, and thermal testing [26, Schwartz]. See paragraph 3.3.7 for further
insight on this subject.
The parts control program (mentioned above with respect to the RI systems engineering
effort) was controlled by the JPO and was a significant systems engineering effort. The program
was maintained under the Systems Engineering Directorate. The Configuration Control Board
(CCB), administrated under this directorate, maintained configuration management of the parts
program process [25, Scheerer]. There were small sets of S-level and JAN X parts approved by
the government at this time. The cost and schedule associated with developing new S-level parts
unique for GPS was prohibitive. Rockwell, with JPO concurrence, pursued the S-equivalent
approach that took existing non-S-level approved parts and established stringent screening
processes to attain a space-reliable part that met its allocated availability/reliability requirement.
The GPS Block I parts program and unique requirements/verification processes established
for S-equivalent and JAN X-equivalent parts was the basis for most of the thinking, require-
ments, and processes that went into MIL-STD-1546 (USAF): Parts, Materials and Processes
Standardization Control and Management Program for Spacecraft and Launch Vehicles (12 Feb
1981 original release), and MIL-STD-1547: Electronic Parts, Material and Processes for Space
and Launch Vehicles (31 Oct 1981 original release) [21 Reaser].
RI’s approach to system requirements and design also included consideration of Factory-
to-Pad logistic operations. Mr. Dick Schwartz, RI GPS program manger, stated, “I think this
(Factory-to-Pad) was an Aerospace (Corporation) idea and a good one. After thermal vacuum we
configured the space craft for shipment, performed a final factory functional (FFF), placed the
satellite on a truck, and delivered to the pad. The truck backed up to the booster at VAFB and the
satellite was placed on the booster. We then had a short test to assure that no damage occurred in
transportation and were ready to launch” (Ref. 37).
3.4.6 Atomic Clocks
One of the major challenges for Block I was to develop a space-qualified clock based upon
the data and lessons learned from TIMATION and the NTS program. The original baseline for
the Block I was that each satellite would contain two Rubidium (Rb) and one Cesium (Cs)
atomic clocks after SVN #3. As it turned out, however, three Rb clocks were flown on SVN 1, 2,
and 3, and 2 Rb and one second-generation preproduction model Cs clock was incorporated after
SVN#3. The Cs clock was referred to as a Pre-Production Model (PPM) and was derived from
the NTS-2 Cs clock [30, White]. The top-level requirements were clock stability and a service
design life requirement of five years. Embedded in the service life requirement was the ability to
withstand the space environment, especially thermal and radiation effects. NRL had adequately
addressed the radiation effects on the clocks in the early phase of this program [21, Reaser]. Ten
51
Block I SVs were successfully inserted into orbit. The SVs generally operated between 8-14
years with, “…a majority of the clocks performing well beyond their expected life expectancy”
(Ref. 31).
In this phase of the program, Rockwell was responsible for the development of the Rb
atomic clocks. Radiation environment data was available and there were documented lessons
learned from the TIMATION and NTS effort. The challenge for Rockwell was the Rb lamp,
which was a high-risk effort. RI utilized technical expertise from Aerospace Corporation to
resolve issues with the lamp. A rigorous ground test with actual hardware was conducted to
verify thermal, radiation, and life cycle requirements [8, Fruehauf].
Beginning with Block I, Rockwell’s baseline clock consisted of Rockwell-Efratom pro-
duced Rb clocks. The initial Block I satellites flew three Rb clocks and no Cs units. Toward the
final Block I program, Cs was introduced. For Block II/IIA, two Rb clocks and two Cs FTS
clocks were established as the baseline configuration per satellite. Originally, the Cs clocks were
to be provided by three different companies, with Frequency and Time Systems (FTS) supplying
the majority of the Cs clocks. NRL, funded by the Navy, conducted a second source develop-
ment effort for Cs clocks with FEI and Kernco. However, none of the alternate clocks ever
became operational on a GPS satellite. Several second-source Cs clocks flew on Block IIA SVs.
A Block II Cs atomic clock is shown in Figure 3-13.
Figure 3-13. Block II Cesium Atomic Clock (Ref. 50)
In Block IIR, a second source effort was directed by the JPO to control cost and schedule.
Under RI contract, EE&G was selected to build the Rb clocks and qualified the clock for the
space environment [21, Reaser].
One of the major program issues is the manufacturing base for space-qualified atomic
clocks. The program purchases clocks in small lots, e.g. approximately 30-40 per lot, with a lull
in lot orders for many years. There is no other commercial or military need for this space-
qualified product. As a result, the clock vendors are not stable, and companies either lose their
expertise and corporate knowledge or go out of business. For Phase IIR, the plan was to have
(Cs) and (Rb) clocks on board the SV. The Cs clocks were to be built by SCI using technology
transferred from Kernco. The technology transfer was not successful and the SCI clocks were
never suitably qualified for space environment. Hence, the SV segment baselined three (Rb)
52
Perkin Elmer clocks and no Cs clocks for Phase IIR. A summary of the atomic clocks used in the
SVs for the various phases is listed in Table 3-8.
The problem of atomic clock supply worsened as GPS became successful and more
widely used. GPS became the global standard for accurate time, thereby further shrinking the
market for atomic clocks. As this market shrinks, it becomes even more difficult for the GPS
program to buy the clocks it needs to maintain the global time standard. Ironically, the
program’s success is killing the market for its own critical component.
Table 3-8. GPS Atomic Clocks [8, Fruehauf, 21 Reaser, 30 White]
Rb Clocks Cs Clocks
NTS-1
Two modified commercial Efratom
clocks (also, 1 high-quality quartz
oscillator) under contract to NRL
NTS-2 Two space-qualified FTS under contract to NRL
Block I
Three Rockwell-Efratom clocks
(SVN #1, 2 & 3); two Rockwell-
Efratom clocks for SVN #4+
No clocks for SVN #1, 2 & 3; one
FTS for SVN #4+ (NRL contract)
Block II/IIA Two Rockwell-Efratom clocks Two FTS under contract to RI
Block IIR Three EG&G (Perkin Elmer) under contract to RI
3.4.7 Control Segment
The ground support system located at VAFB and the remote sites (referred to as the ICS)
were established for the concept validation phase and upgraded as required to support the Block I
SVs. This was primarily a software upgrade. The ICS had to address navigation critical systems,
ephemeris algorithms, L-band signals, clock state, time transfer, processing uploads, and control
of SV. The concept of selective availability during this Block I effort was unclassified, which
eliminated any requirement for classified crypto equipment. ICDs between Maser Control Station
(MCS) and remote sites were updated. Interfaces with USNO through ICDs were also established
with respect to time transfer and updates from USNO.
This phase of the program became the first real instance of operational commands
supporting the program. Around 1980, HQ SAC took on the responsibility of being the operator
of ICS. Training was accomplished primarily through on-the-job training from the JPO and the
contractor, IBM. HQ SAC handpicked their operators, and they were all engineers [16,
Nakamura]. This approach had the additional benefit of having the operators perform some
limited troubleshooting. SAC also established a liaison officer at JPO and provided guidance in
developing operating concepts for the control segment. Established ICDs between MCS and
remote sites were updated.
In the early 1980s, a major Air Force trade study investigated whether Fortuna AFS or
Colorado Springs, CO would be best suited to house the AF Consolidated Space Operations Center
(CSOC). Colorado Springs was selected. Falcon AFB, which eventually became Schriever AFB,
was established as the location for CSOC and the GPS Master Control Station that would be part
53
of this complex. This selection would impact requirements relating to the development of the
Operational Control System (OCS) in the next phase.
USNO had the responsibility for precise time. One of the requirements for GPS is that it
provides a worldwide time reference system for UTC (USNO) to every GPS user. To ensure the
accuracy of the SV signal transmission, the USNO needs to receive GPS time and UTC (USNO)
from the SVs and compare it with the USNO master clock. Corrections in terms of time bias and
drift offset were transmitted to the GPS MCS for upload to the SVs. An ICD was established
with the GPS CS. In 1978, USNO in coordination with the JPO contracted with Stanford
Telecommunications to build the time transfer unit receiver in the Washington, DC area. The
system became operational in 1979. Only one satellite is required to receive the precise time,
assuming that the user already knows their precise position [19, Powers]. It should be noted that
there were several users, especially in the commercial world, that value the GPS precise time
over the GPS position data, as they already know their precise position. Early in the program
with only a few satellites, some users bought GPS sets just for precise time. Today, virtually all
bank transactions are date stamped with GPS time and most communication networks are
synchronized with GPS time [25, Scheerer].
The SV design had an impact on the CS procedures. Orientation of the thruster rocket
plume had an adverse affect on the solar panel in certain orientations (low beta angle with respect
to the sun) that created a momentum reaction, making the vehicle unstable. One of the initial
Navigational Development Satellites became unstable during a maneuver and had to be
recovered over a two-week time span. No design changes were made to the SVs in this phase.
Procedure precautions were used to ensure that thrusters were not used when beta was low [16,
Nakamura].
3.4.8 User Equipment
One of the more important decisions made early in the program with respect to UE was
based upon a system trade study. It established in the system architecture that there would be a
minimum of four SVs above the horizon at all times. This allowed the development of receivers
with inexpensive crystal oscillators in lieu of precision atomic clocks. The UE measures the dif-
ference between the time of transmission of the signal by the SV and the time of reception of the
signal by the UE to determine the three-dimensional position of the UE. With three satellites, a
very precise time source would be required. However, with a fourth satellite, the fourth dimen-
sion of precise time can be determined and a quartz oscillator can be used by the UE to provide
the required accuracy. This decision avoided cost and potential weight/size impacts and opera-
tional utility impacts to the UE.
The decision to avoid precise clocks in the UE by keeping four satellites in view
was a distinguishing factor in selecting TIMATION versus 621B. TIMATION used the fourth
satellite for precise time, and 621B incorporated clocks in the UE. This key long term decision
makes UE cheap at the cost of more expensive constellations. For the commercial users, this is a
major benefit.
The program continually used a risk reduction philosophy of funding studies or designs to a
multitude of sources, and then conducting a down-select. The competition among the contractors
54
provided investigation of new and innovative ideas, and also tailored costs. The program further
reduced risk in that the multi-contracts usually were completed at a System Design Review (SDR)-
or Preliminary Design Review (PDR)-type design. This approach allowed a better understanding
of the events, schedule, cost, and risk in the next phase, and therefore could be better scoped in
the RFP, proposal, and contract. However, this approach required both good planning knowledge
as to when to implement this philosophy, and up-front funding to contract with multiple sources.
This phase of the program for UE was divided into a Phase IIA and Phase IIB. In July 1979,
the JPO awarded Phase IIA fixed-price contracts to Magnavox, Texas Instruments, Rockwell
Collins, and Teledyne for pre-design/performance analysis.
In 1982, a down-select occurred (Ref. 3). Magnavox and Rockwell Collins were both
awarded Phase IIB contracts to continue development by refining requirements, fabricating proto-
types, completing design, conducting qualification testing, and accomplishing extensive field
testing. Most of the field testing was conducted at YPG and the Naval Ocean Systems Center at
San Diego, CA.
The Rockwell Collins process stressed a firm architecture supported by analysis. Their
intent was to ensure that manufacturing/quality assurance were involved in the design process
and strove for simplicity/commonality in the design. During this phase, Rockwell Collins used a
modular approach that included a flexible module interface concept, by which modules were
bolted to a common GPS receiver. This approach allowed commonality for various aircraft and
reduced schedule and technical risk. Human factors played an important role in the man-machine
interface, especially with the soldier variant [14, Krishnamurti].
As the number of users was increasing, both amongst the services and internationally, a
new trend emerged: some of these users were providing requirements directly to the contractor.
The systems engineering process was reemphasized with the need to utilize services and
international representatives within the JPO. This required the JPO to perform a systematic
assessment to both validate and track the requirements. [24, Saad].
A major issue arose in the security classification requirements of the UE during the devel-
opment of Selective Availability (SA) and Anti-Spoofing (AS) (SAAS) software12.13 National
Security Agency (NSA) staff concluded that the UE should be considered a crypto device. This
“new” requirement was assessed by the JPO. The systems engineering analysis identified major
consequences to the GPS design and operations if this requirement was implemented. The
CONOPS would be adversely affected due to the additional security needed in the field. The
analysis also concluded that there would be potential impacts by adding another required Line
Replaceable Unit (LRU) to the design to accommodate the new security requirement. An
example of these impacts was that the manpack would have had a 15 pound additional LRU
added to a device that already had a weight concern of ~10-15 pounds for manned portability.
Several JPO discussions with NSA about the new requirement resulted in no mutual resolution,
and NSA officials suggested alternative designs. The JPO systems engineering process assessed
the alternative designs and found them inappropriate with respect to meeting other GPS
requirements. The JPO continued their systems engineering process addressing CONOPS,
12 SA was solely software and AS was both hardware and software.
55
mission analysis, requirements and design analysis including security, and developed their own
approach to the cryptology methodology. The issue finally worked its way up to the NSA Senior
Manager. He considered aspects of the issue including the JPO approach, and resolved the matter
by approving the JPO approach. After this, the JPO and NSA had a very constructive working
relationship [25, Scheerer].
3.4.9 Design Reviews
Classic Preliminary Design Reviews (PDRs) and Critical Design Reviews (CDRs) were
conducted in each of the GPS segments. MIL-STD-1521, “Technical Reviews and Audits for
Systems, Equipments, and Computer Software,” was used as the basis of the design reviews. The
standard was cancelled by the DoD later in the program; however, its use set up a valuable
process for conducting the reviews and audits [16, Nakamura].
There was no overall GPS Systems PDR and CDR conducted. The JPO, as the system
integrator, with technical assistance of Aerospace Corporation, verified compliance of segment
designs to the system specification and the system architecture controlled by the JPO. This veri-
fication was an ongoing effort. In some cases, the ICWG process resulted in meetings that were
more like a technical interchange meeting or mini-design review, to which the meeting would
define the next phase of effort based upon the segments design status [21, Reaser]. This defi-
nitely was the case with the UE segment for both PDRs and CDRs. The host platform UE design
reviews were informally conducted at the ICWG meetings for that UE receiver class. Types of
classes for receivers included portable (soldier/land vehicles), aircraft medium dynamics
(helicopters), aircraft high dynamics, and ships. The UE system segment specification design
reviews, both PDR and CDR, covered all class receivers together [14, Krishnamurti]. In general,
any requirement that had a “to-be-determined” status at PDR was deferred to the next upgrade
program [24, Saad].
From one perspective, the ICWGs could have been considered more important as a
design risk mitigation process than the typical design reviews. Issues were worked in real time
and incrementally with a very structured process that tracked actions and was well-supported by
the government and contractors.
3.4.10 System Integration
The JPO actually became involved in the aircraft integration to the dismay of several air-
craft program offices. However, the JPO in-depth knowledge base and lessons learned from the
concept validation and early system development phases were important to ensure that
integration requirements were clearly defined and that there was a clear means of requirement
verification. In the late 1970s and early 1980s, the program was also trying to survive among bud-
get cuts and perception of cancellation. The JPO motivation was to ensure successful integration
of the UE on the host platform to establish another alliance to justify proceeding with the
program [21, Reaser].
3.4.11 ICWG
The ICDs were maturing as the requirements analysis was concluding and new require-
ments were being added to the program in this phase. Additional interfaces and ICDs were also
required as a result of requirements development and new requirements.
56
NRL: Atomic clocks
USNO: Precise time
NSA: S/A & AS
DOE (Sandia and Los Alamos): IONDS
The ICWGs were an excellent means to communicate, coordinate interfaces, assess design
changes, and resolve problems [8, Fruehauf].
3.5 Production and Deployment (Phase III, Block II/IIA)
3.5.1 Objective
The objectives of Block II were to “fine-tune loose ends” of the development and issue
production contracts for 28 SVs [22, Reynolds]. An initial operational capability would be obtained
with a mix of Block I and Block II satellites and a full operational capability with all Block II
satellites. The SVs would be launched from the Space Shuttle.
Block II would include improved NDS and SV operating autonomy (ability to operate
without contact from CS up to 180 days), Anti-Spoofing and Selective Availability capabilities,
and radiation-hardened electronics to improve reliability and survivability.
3.5.2 Acquisition Strategy
The strategy developed by the JPO was to procure the SVs like an aircraft system, a new
approach for the space community. There would be a “lot buy,” basically a block buy of the SVs.
This not only was a cost benefit, but also minimized the approval cycles through the Air Force
by conducting a concurrent effort in developing the enhancements and incorporating them into a
production contract [22, Reynolds]. The JPO had developed a Technical Requirement Document
for this phase. The requirement for the W-Sensor of the NDS was added at a later time and the
decision was originally made to allow for production incorporation at the 13th satellite.
Since the directed baseline launch vehicle was the Space Shuttle, the Air Force awarded a
fixed-price contract to McDonnell Douglas to purchase 28 upper stage boosters called Payload
Assist Modules (PAM-DII). Also, a separate cost-plus-support service contract was negotiated.
The SV segment contract required concurrence by RI, who was reluctant to sign up to a
firm-fixed-price contract based upon their perceived risk. A team of Rockwell, subcontractors,
vendors, manufacturing community, JPO, and Aerospace Corporation formulated the development
plan/program. This included an extensive study of the assembly line at the Rockwell Facility at
Seal Beach, CA. The team established an acceptable final program [22, Reynolds].
3.5.3 Nuclear Detection System
Early in Block I, the GPS program was tasked to include an IONDS as a secondary pay-
load on the SV. The NDS provided a worldwide capability to detect, locate, and report nuclear
detonations in the earth’s atmosphere or in near-earth space in near-real-time. The GPS was an
ideal system to implement this capability, as the GPS functional baseline also required world-
wide coverage for navigation that was implemented by the constellation configuration. The JPO
did not have a requirement for the other elements of NDS: the NDS control segment and the
NDS user equipment. The NDS sensors were developed by Sandia National Laboratories/Los
57
Alamos National Laboratory and provided GFE to Rockwell. The Air Force and the Department
of Energy established a Memorandum of Understanding resulting in new development ICDs and
some existing ICDs being modified for the interface with the system. Integration of the sensors
into the SV created no significant issues.
For Block II, the Air force established a requirement to upgrade to the IONDS system. The
Nuclear Detonation (NUDET) Detection System (NDS) consisted of an optical sensor (Y-
sensor), an X-ray sensor, a dosimeter, and an Electro-Magnetic Pulse (EMP) sensor (W-sensor).
The W-sensor was a new function on the NDS. Sandia National Laboratories/Los Alamos
National Laboratories developed he NDS sensors with the exception of the W-sensor. The JPO
made a decision, based upon the projected schedule for the integration development effort driven
by the W-sensor, to incorporate the NDS change later in Block II. The tenth Block II SV
incorporated the NDS capability, and the NDS GPS satellites received the designation Block IIA.
The functional baseline was adjusted for this new capability. Follow-on Block IIR SVs also
included this capability.
The systems engineering process identified a technical risk of integrating the W-sensor at
the beginning of the program. As the integration effort continued, the task became more
technically challenging than anticipated. The levels of EMI/EMC were far more sensitive than
anticipated; i.e. in the 50-150 MHZ range. The basic concept was to make the SV a very good
Faraday cage. Sandia National Laboratories would not sign up to develop the W-sensor, so
Rockwell International was given the contractual responsibility for the development and
contracted with E-Systems to provide the sensor. Sandia National Laboratories continued to
provide technical support sensors [21, Reaser].
Gold foil wrap was added to the SV for electro-magnetic protection for the sensitivity of
the W-sensor. However, the SV solar panel motors emitted sufficient energy through the motor
shafts that extended beyond the wrap. The W-sensor was detecting this energy. The simplest
design fix for the already-designed and validated solar panel system was to add “fingers” to ground
array shaft pads. This design approach presented an issue of meeting the lifetime requirement.
The material of the “fingers”, which were in contact with the motor shaft, had to withstand suffi-
cient life cycles without the material wearing away.
Significant studies and testing were required to define the appropriate materials for the
“fingers”. Ball Aerospace, in Boulder, was contacted to determine the material required for
fingers. RI and JPO were deeply involved in the assessment. Many combinations of alloys were
manufactured and tested until an Au/Ni alloy was successfully verified to meet all requirements.
As Block II was a production contract with concurrent development in specific areas, the
additional effort on the W-sensor was added via an H-clause in the contract. The schedule was
not impacted as a result of intense effort, due to the proactive role of the team members [23,
Robertson].
Integration of the X- and Y-sensors and dosimeter did not create any significant issues, as they
had been integrated on other satellites. The verification of the W-sensor required RI to
build a high-fidelity anechoic chamber. This effort resulted in a 12-14 month schedule impact.
The cost to the W-sensor integration was $162M [23, Robertson].
58
The gold foil wrap around most of the SV resulted in a buildup of electro-magnetic energy
within the volume contained by the foil. The solar panel drive motor control system utilized a
1960s-type technology design with fusible links. There were redundant circuits (A & B strings).
The combination of the noise energy and the command signal resulted in activation of a fusible
link on SV-23. The consequence was that there were dual, but opposite, commands sent to the
drive system. The interim operational fix was a procedural approach by which the control station
would manually slew the arrays, which was a burden to the operators. The corrective action was
to incorporate a static trap with a diode and capacitor added to the circuit. This design change
was incorporated at a later time. The overall issue was a lack of a complete assessment of the
internal satellite interface requirements and assessing the impact of the gold foil wrap design
change on existing systems [18, Paul]. A Block IIA satellite is shown in Figure 3-14.
Pr
ov
id
ed
b
y
H
ug
o
Fr
ue
ha
uf
Figure 3-14. Block IIA Satellite
3.5.4 Shuttle Impact to Functional Baseline
The original Phase I plan for launching the Block II SVs was to use an expendable launch
vehicle. The projected increased weight of the Block II SVs over the Block I SVs exceeded the
Atlas series rocket payload capability by approximately 800 pounds. Delta rockets were the pre-
ferred approach for the Block II SVs. However, Dr. Hans Mark, Secretary of the Air Force,
issued a directive around 1979 to exclusively use the shuttle as a launch platform for all Air
Force space vehicles. This implemented President Carter’s directive in the revised National Space
Policy for all DoD to launch platforms from the space shuttle to “…take advantage of the
flexibility of the space shuttle to reduce operating costs over the next two decades” (Ref. 34). This
program requirement had a significant impact on the SV performance requirements.
The systems engineering process addressed the requirements and risk associated with
launching from the shuttle. The shuttle was man-rated, which required triple inhibits to cata-
strophic risks and safe arm controls. It also required a shuttle mission specialist interface for
launching from the Shuttle. In addition, analysis of the shuttle environment showed it to be more
severe than normal expendable launch vehicles. An analysis of the shuttle bay capacity
concluded that four GPS SVs with their required Transfer Orbit Stage and common airborne
support equipment could be accommodated on one shuttle mission. Performance and interface
requirements were incorporated into the Block II/Phase III Technical Requirements Document
(TRD) (Ref. 44). The necessary MOUs and ICDs were established with NASA. A detailed Payload
Integration Plan was developed for the SVs that complied with all NASA policies, regulations
and requirements, and was updated on a periodic basis. The JPO conducted a cost-benefit
59
analysis and determined that a lot procurement of Payload Assist Modules (PAM-DII) tailored in
design for the GPS shuttle launches was cost effective [27, Sponable]. Figure 3-15 shows the
interface and elements/subsystems of the SV and the Shuttle (DoD Space Transportation
System).
Figure 3-15. Space Segment System Relationship (Ref. 44)
As the development of the Block II SV continued, weight growth became an issue. Early
assessments identified the weight risk to the requirement of four SVs per shuttle mission and that
the capacity may be only three per mission [27, Sponable]. The JPO was reviewing the actual
operational launching of four satellites with respect to the risk of putting four satellites on one
launch vehicle. An additional concern was the potentially lower priority GPS would receive in
the shuttle manifest.
When the Space Shuttle Challenger disaster occurred in January 1986, the JPO had to de-
velop a risk mitigation plan. There was no backup or funding for alternative launch vehicles. It soon
became apparent that the shuttle would not be available for operations for some unknown time. Ini-
tial estimates of a six-month slippage kept growing. Further implications were that the shuttle
facilities at VAFB ended after design changes in the shuttle diminished its capability for polar
launches. These were key issues for all DoD launches. Eventually, the Air Force decided to contract
for expendable launch vehicles on a high priority. To maximize launch flexibility, the JPO
pursued a dual-access capability by establishing a baseline interface requirement for the Block II
SV design. The interface could support either launch on the shuttle or a number of alternative
expendable launch vehicles (ELVs). After a while, the shuttle launch requirement was
60
completely withdrawn, and no DoD satellites were allowed to use the shuttle. The severe
environmental requirements driven by the shuttle compatibility required minimal changes for
flight on ELVs, which helped expedite the transition to future ELV boosters [27, Sponable]. The
functional baseline was again updated.
The acquisition approach for the ELV development followed the typical JPO risk mitiga-
tion approach by awarding the three $6M fixed-price contracts to develop preliminary designs and
then down-selecting and awarding to the winning contractor. The Titan 3 rocket (Martin Marietta)
had the ability to launch two SVs at once, but presented a problem in getting the SV to separate and
transfer into a potentially different orbital plane. The Atlas Centaur rocket (General Dynamics)
included a liquid-fueled third stage and the system had a significant cost impact. The Delta II
(McDonnell Douglas) was ultimately selected, due to its lower cost and historical reliability. This
design selection was a modification of the previous Delta rocket, stretching it about 20 feet and
adding the bulbous fairing. The design of the fairing had a benefit that some of the SVs antennas
did not have to be stowed during launch, which would aid reliability requirements [23,
Robertson]. The Delta II was developed in two consecutive configurations: the first (Delta 6000)
with an approximate payload capacity of 3670 lbs and the second (Delta 7000). The rationale for
the two configurations was driven by the need to achieve a first launch date in 1989. A lighter
payload version of the Delta II could meet the objective launch date (Ref. 33). The larger 4470 lb
payload configuration for the heavier Block IIA SV with the NDS payload required more
development time (Ref. 10).
The JPO developed a plan to use the shuttle as a launch vehicle in parallel with the ELVs
when the shuttle became operational again. The number of SV launches in the revised plan was
originally 16 and then reduced to eight as the shuttle return-to-launch schedule slipped. Compli-
cating this plan was the backlog of higher-priority satellites/payloads from other programs that
could impact the GPS schedule (Ref. 33). Eventually, the decision was made not to use the
shuttle.
A very structured process was established for the new ELVs and SVs. Lessons learned
from launches were reviewed prior to each new launch. An Independent Readiness Review Team
(IRRT) conducted a review of all qualification/verification items prior to the first launch of a new
system/subsystem [23, Robertson]. Considering the commitment to develop a launch vehicle quickly,
a reliable ELV source was developed in about two years. This would culminate in 28
consecutive successful launches of the Block II/IIA SVs. Key systems engineering processes that
helped the program were: risk identification/mitigation, good requirements development, and good
interface definition. Figure 3.16 shows a launch of a GPS SV on a Delta II rocket.
U
S
A
ir
F
or
ce
p
ho
to
61
Figure 3-16. Delta II Launch of Block II Satellites
The systems engineering process was used to account for the change in the functional base-
line requirement, time lines, and concept of operations with respect to logistics of the SV coming
off the production line. The GPS program was the first satellite program to have such a large
production run. The lengthy delay until first launch presented another dilemma for the JPO, namely,
what to do with the satellites that were scheduled to come off the production line while they were
waiting for flight. The SV design did not account for extreme lengthy delays before launch. The
JPO tasked Rockwell to initiate a three-month systems engineering study of three options: stop
production, slow the production rate, or continue the production rate and develop a storage plan
and facility. The conclusion of the study was to slow down the rate of production based upon the
assessment that the ELV would be available in approximately two years. This recommendation
was implemented [23, Robertson].
The lot buy of PAM-DII units for use on the shuttle was now obsolete. The cost avoid-
ance approach with a multi-year contract unfortunately became a burden, as there was no need
for these 28 unique PAM-DIIs for shuttle use. The JPO cancelled contracts for these boosters,
which resulted in not buying the last 12 units (Ref. 33). In this particular case, the risk of the lot
buy was accepted based upon a firm requirement from the Secretary of the Air Force committing
to the shuttle and a good cost-benefit analysis [21, Reaser].
The Challenger disaster had one benefit to the GPS program, in that it provided
schedule relief. The CS had software problems and there was a moderate-to-high risk of not
meeting the original launch date of late 1986. There was an extensive ongoing effort by the
contractor, Aerospace Corporation, and the JPO to resolve the issues. One of the key issues
included verification of selective availability. CS software releases were not complete and
probably would not have supported the Block II SVs on the initial program schedule [20, Prouty].
The final operational release of the software occurred just a few months before the first Block II
launch in February 1989. The delay in launching SVs into orbit adversely affected the UE
developmental testing, which had planned on using early Block II SVs.
3.5.5 User Equipment (UE) Development Testing Effects
In April 1985, the JPO awarded the first Low Rate Initial Production Contract (LRIP) to
Rockwell Collins. The contract included research and development, as well as production options
for 1-, 2-, and 5-channel GPS airborne, shipboard, and manpack (portable) receivers. This allowed
the UE to be cut into the F-16 production line. Initial JPO developments and procurements were
exclusively Line Replaceable Units (LRUs), or “boxes”, which included the 3A receiver for high-
dynamic aircraft applications, the 3S receiver for shipboard applications, and the manpack (Figure
3-17 shows the Rockwell Collins version of the manpack). These were followed by the smaller
and lighter Miniaturized Airborne GPS Receivers (MAGR) for high- and medium-dynamic aircraft.
62
Figure 3-17. Rockwell Collins Manpack (Ref. 47)
Aerospace Corp. conducted a threat assessment study for UE receivers. The JPO Systems
Engineering Directorate followed up with an assessment of the Fixed Reception Pattern Antenna
(FRPA) and Controlled Reception Pattern Antenna (CRPA) and how a common antenna could
satisfy all user requirements and save cost through common support and larger procurement of
units. Due to the orthogonal capability of the CRPA, it was more effective in countering the threats.
However, at that time, the CRPA was more complex and approximately three times more costly
than the FRPA. The Navy originally selected the FRPA for its aircraft and then, years later,
replaced it with the CRPA [18, Paul].
There were delays in completing the UE: “…operational testing as a result of lingering
receiver reliability problems and reevaluation of program requirements (that) …caused DoD to
postpone the GPS receiver set full rate production decision until Sept. 1991, a decision originally
scheduled for March 1989” (Ref. 38). The UE reliability requirements are included with other Test
and Evaluation Management Plan (TEMP) operational system performance requirements pro-
vided in Appendix 8 (Ref. 39). Delays in accomplishing operational testing of various receiver
sets caused DoD to initially postpone operational testing until June 1990. The delays were caused
by problems in integrating receiver sets with host aircraft and ships, late deliveries of receivers,
availability of military personnel to conduct Army one- and two- channel tests, and the space
shuttle accident which delayed launches of SVs needed for testing. On 21 Sep 1990, the Under
Secretary of Defense for Acquisition postponed a full-rate production for all receiver sets until
Sept. 1991. But, he approved continuing LRIP for one-, two-, and five-channel receivers
through FY 1991, and recommended additional testing of the five-channel receiver sets. Five
LRIP contracts were awarded to four contractors including Rockwell Collins, the initial LRIP
contractor. The DSARC IIIB was further slipped to March 1992 (Ref. 40).
3.5.6 Control Segment
The program needed to develop an operational control segment to replace the ICS as the
Block II SV came on line. There was also a need to upgrade the ICS to ensure continued support
to the UE segment for their testing while the OCS was being developed. These two tasks were to
be combined under one contractor effort. In the typical risk mitigation approach, five bidders
were awarded contracts for concept design studies based upon the CS functional requirements.
Upon completion of the studies, there was a down-select to three contractors: IBM Gaithersburg,
Martin Marietta, and General Dynamics. This contractual effort continued to further develop the
concepts and refine functional requirements, resulting in a pre-SDR functional baseline stage. IBM
63
and Martin Marietta worked to develop prototype labs and modeled receivers. General Dynamics
had been the contractor during the previous phase. Again, a down-select occurred – this time,
based upon the functional baseline established, IBM was selected for the continuing
development. The JPO had difficulty getting IBM’s agreement to requirements because of the
fluidity of the program. The JPO incentivized the contractual effort and IBM agreed to the effort
[16, Nakamura]. The contract was awarded in September 1980. The Block II schedule also was
aggressive and left no margin for issue resolution. Figure 3-18 illustrates the OCS top-level
system diagram with functional and support groups identified.
IBM had a core of seven to eight personnel with support from other groups. They had no
previous space background in this division of IBM, but had solid systems engineering processes,
a good system architecture, and documented system testing and tools [2, Berg]. The JPO
augmented their lack of domain knowledge with experienced systems engineering people.
Aerospace Corporation also provided key technical support. The IBM program approach was to
have parallel paths for both program management and the technical group directly to the program
director. This approach ensured that the technical side of the program would have opportunity to
present their position to upper management when there was disagreement with program
management [3, Conley]. The control segment process established system requirements and a
specification tree; established functional block diagrams, physical block diagrams, and internal
ICDs; and allocated requirements within the organization and to subcontractors and vendors.
The NDS requirements for the CS were minor. The roles and mission of the CS had to be
defined in order to allocate the appropriate NDS functional requirements to the CS. CS was
neither responsible for the receipt of the L3 signal nor the functioning of the NDS system. Their
responsibilities encompassed performing the NDS command and control of the SV as required
by the user, identifying the health of the NDS system, and controlling the ambient environment
(e.g. temperature) in the vicinity of the NDS.
The program offices, both at the JPO and the contractors, knew that the software and error
budget were high risk. The mitigation plan was to develop simulation and modeling to validate
the software designs. Also, a national team of experts from government and industry, including
the National Bureau of Standards, assisted in trying to resolve the modeling of the atomic clock.
Ephemeris models were also creating problems. The TPMs used to track the software were pri-
marily software lines of code (SLOC) and defect testing. The selective availability requirement
was not well defined and was open to several different interpretations. Validation of selective avail-
ability created issues in terms of requirement verification interpretation. Also, there was no tool
to analyze the validity of the crypto data. An original estimate of the size of the CS software was
300K-400K software lines of code [20, Prouty]. The final size was 1.1 million lines of code [24,
Saad]. Testing of the software was in the traditional method of unit, subsystem, and system tests,
with FCA and PCA being accomplished at the appropriate levels [16, Nakamura]. Some of these
issues were a result of the lack of tools to estimate design detail, the lack of clear definition on
requirements, and an upfront understanding of verification approach/method required. However,
the systems engineering process was used in successful resolution of the issues.
64
Figure 3-18. Operational Control System Top Level System Diagram (Ref. 43)
Initial CS software releases were in support of the Block I SV capability only. This allowed the
OCS at VAFB to become operational in 1985. The accomplishment was made easier by the lack
of Selective Availability encryption requirements for these releases that created challenges in
Block II. (Note: Encryption was still required for satellite command uplink and data to/from the
ground antennas to the MCS).
65
There was an extensive effort in the 1986 to 1989 period to resolve the Block II software
problems. Validation and verification became a major issue with the software effort. One of the
first problems was getting configuration designs and simulations from Rockwell. It was difficult to
test the interface with the SV in the lab and a field effort was required. After JPO and Aerospace
Corporation initiatives with Rockwell, a plan was devised and implemented to take Block II quali-
fication boxes and rack, and upgrade the Block I simulator to a Block II configuration. The simu-
lators were taken to Cape Canaveral in 1987-19
88
for an extensive, almost full-time, 15-month effort
allowing IBM to validate the upload and receive capability and interfaces of the CS [3, Conley].
Aerospace Corporation provided additional support to IBM in the transition of the OCS from
Vandenberg AFB to Falcon AFB (now Schriever AFB) with permanent on-site support. This
effort was the key to success of a final software release. IBM also developed operator and field
manuals. The final software release (version 3) occurred in 1989, just in time for Block II initial
launch with Delta rockets.
Training requirements for the CS were addressed by forming working groups consisting
of the JPO, Aerospace Corporation, contractors, and operational personnel. Space Command had
been recently formed and had taken over operations responsibility from SAC. There were no
Space Command requirements. Interface meetings were established with Space Command.
However, lack of continuity of key personnel within this new command resulted in different
perceptions and needs, creating additional issues to address. A clear and concise MOA was
established between JPO and AFSPC on responsibilities related to the control of Block II SVs
when in orbit, especially when the JPO wanted to conduct system tests: e.g., deficiency report
resolution verification, CS upgrade verification, the Y-sensor system level test, etc.
The SV constellation baseline had been 18 satellites, based upon funding issues early in
the program that had reduced the constellation from the original 24-constellation configuration.
In 1987, detailed systems engineering analysis was conducted to determine the limitations of the
18-satellite constellation configuration. The JPO then briefed the limitations of the 18-satellite
constellation to the operating commanders, on-site, at various locations around the world.
Messages were soon received from these commands stating that the limitations of the 18-satellite
constellation were not acceptable and that a larger constellation configuration should be pursued.
During this timeframe, the Air Force initiated a trade study of cost-versus-performance and was
interested in reducing the constellation to a two-dimensional 12-satellite configuration and
queried the JPO about approach. The JPO already had the answer in terms of current 18-
constellation limitations and what the real warfighter needed. The requirement driven by
operational commands became a 24-satellite constellation and the Air Force would provide
funding to support this requirement [11, Green]. This appears to be one of the first times that the
operational commands became advocates of the program.
Trade studies and additional system assessments of the 24-constellation configuration
were conducted by the JPO with technical assistance from Aerospace Corporation. Drs. Rhodus
and Massatt of Aerospace Corporation, in coordination with the JPO, conducted an analysis of
the constellation configuration. They considered configurations that were less sensitive to satellite
drift and would be more robust during multiple satellite failures, resulting in an asymmetrical
design of the SVs location – see Figure 3-19 (Ref. 18). The functional baseline was updated for
the latest satellite constellation configuration (Ref. 18).
66
Figure 3-19. 24-Satellite Constellation (Ref. 49)
3.5.7 Requirements Validation & Verification
The JPO and Rockwell jointly established a Satellite Test Criteria Review Board
(TCRB), which conducted a rigorous review of all SV qualification and acceptance testing
during Block I [23, Robertson]. The TCRB was a contractual solution due to the JPO last-minute
substitution of MIL-STD-1540A for MIL-STD-1540 (Test Requirements for Launch, Upper-
Stage and Space Vehicles) in the Block I contract. Rockwell apparently did not realize the change,
and the satellite and vendor programs were not in compliance [21, Reaser]. Weekly well-structured
meetings were conducted with extensive efforts to validate qualification requirements and
determine the root cause before concurrence or approval to proceed to the next event. The board
consisted of the JPO, prime contractors, vendors, and Aerospace Corporation personnel, with the
JPO contracting office chairing the meetings [21 Reaser; 23 Robertson].
OT&E could not be conducted on the SV. There was a need to conduct joint DT&E and
OT&E. This joint test and evaluation were somewhat unique in this timeframe for the rocket
community and required close coordination with AFOTEC. The key to making and executing the
plan was AFOTEC. They helped ensure early identification of acceptance criteria [18, Paul].
3.6. Replenishment Program Block IIR
3.6.1 Objective
The Block IIR objective was to provide 21 replacement satellites for the Block II/IIA.
Also included were enhancements such as enhanced autonomy, 180-day degradation, increased
radiation hardening, cross-link ranging, hot-backup of clocks, and modernization of parts.
3.6.2 Acquisition Strategy
In accordance with the DSARC II direction to compete the SV contract when the design
stabilized, the JPO developed a competitive acquisition strategy. In typical JPO contractual
fashion, risk mitigation was factored into the strategy. The existing satellites were basically
designed with late 1960s, 1970s, and some early 1980s technologies. Part of the modernization
was to optimize the navigation payload/bus system. For the modernization of the SV navigation
67
payload/satellite bus, three fixed-price contracts were issued: ITT, Rockwell Autonetics, and
Garmin to develop breadboard designs.
The JPO issued two fixed-price contracts for the SV segment design, one each to Rock-
well International and General Electric Aerospace. The contractors were to design up to a PDR
and then there would be a down-select. A caveat was added to this effort: The SV segment con-
tractors were allowed to team with the three vendors developing the breadboard designs for the
navigation payload/bus system. RI teamed with Autonetics and Garmin, and GE with ITT. The
down-select occurred, and General Electric Aerospace was awarded the SV contract on 21 Jun
1989. (Note: Lockheed Martin acquired General Electric Aerospace in 1992). The JPO strategy
of competing initial phases of the program had a significant benefit with respect to produceability
of the Block IIR satellites. Piece parts were reduced by approximately half and touch labor by
approximately two thirds [23, Robertson]. This approach utilized classic systems engineering
principles of conducting detailed trade studies and prototyping prior to PDR to validate the
design concept capability to meet the functional baseline in the most cost-effective manner. The
competition among vendors/contractors was the forcing function to this process.
3.6.3 Requirements
HQ AFSPC acted as the centralized user for the GPS program in terms of coordinating
and integrating user requirements. They established the survivability requirement that was a tech-
nology challenge for the program. The increased requirements for hardening in case of nuclear
detonation in space were beyond the effects of the Van Allen belt radiation requirement. This
hardening requirement was identified as a risk from the initiation of the effort, and a technology
development program was initiated to create hardened processor chips to the levels identified in the
requirement. Once the technology solution of silicon-on-sapphire was identified, a further problem
of yield rate for growing the crystals was addressed and successfully resolved [23, Robertson].
3.6.4 Critical Design Reviews
In Block 2R, the typical JPO philosophy of risk mitigation was applied in that the SV
segment was competed between Rockwell International and General Electric Aerospace. Two
fixed-fee contracts were issued for development up through PDR. A down-select was
accomplished and General Electric won the contract. The governing requirements document for
the initial contract was the Block 2R TRD developed by the JPO. The TRD was a carryover as
the governing system segment document through the initial portion of the effort because of an
issue with the requirement for the NDS W-sensor to operate through a nuclear event in space.
General Electric wanted the system segment specification to be written to allow the NDS to “blink”,
or shutdown and restart, as an interpretation of the requirement. As a result of this non-resolution
of the issue, the TRD remained the functional baseline document until after CDR [23, Robertson].
An unintended error in the contract tied the production option to both the CDR and its
scheduled date and not to the CDR event itself. This presented a dilemma to the JPO. The JPO
assessed that General Electric was not ready for the CDR. Yet, slippage had a major impact on the
production price option, and the JPO did not want to reopen negotiations. The decision made was
to conduct the CDR and exercise the option. The CDR was officially closed with numerous action
items. The risk mitigation plan was to conduct monthly technical interchange meetings to further
assess the design to the allocated baselines and to address outstanding action items [23, Robertson].
Certain programmatic decisions made during the course of a development program may be beyond
68
the classic systems engineering process. The systems engineering process must be flexible enough to
adapt to these conditions and continue to ensure compliance with requirements and risk
avoidance/mitigation. In this case, the design risk was mitigated by the continuance of a structured
process to track the major CDR action items and ensure that the intent of a MIL-STD-1521-type
CDR was closed at a later time. Additionally, the risk of design fabrication was identified and
monitored during this period.
3.6.5 User Equipment
In the late 80s and early 90s, some of the users began to investigate the applicability of
commercial GPS receiver designs to be adapted to the requirements. The Army had purchased
the commercial Small Lightweight GPS Receiver (SLGR) in 1989 for demonstration and
training, and it was not intended to be used in a non-tactical scenario. The manpack was approxi-
mately 8 inches by 12 inches by 18 inches and battery operated, which increased the weight. It
was not very user friendly to the soldier from the field standpoint, although it met the Army’s
performance requirements [14, Krishnamurti]. “To reach a general agreement that an NDI (Non-
Development Item) strategy was feasible, the Army had to make tradeoffs in its requirements.
The commercial products were not expected to match the performance of the AN/PSN-8
manpack, even if the selective availability and anti-spoof modifications were incorporated.
Accordingly, the Army amended its 1979 requirement for the manpack to take advantage of
commercial GPS technology. The intent of the changes was to get a system, as an off-the-shelf
item, that would meet minimum essential requirements, be affordable, be available in the near
term, and be easy to operate. The challenge was to avoid letting ‘better’ be the enemy of ‘good
enough’ by curbing the desires of the design engineers to optimize performance” (Ref. 32). The
JPO and Army still required the selective availability and the anti-spoofing capability, which was
not a capability in the commercial industry. Some minor modification of the design would be
required to meet this performance [14, Krishnamurti]. “During the period November 1990
through June 1991, a government performance specification was coordinated with industry and
the government. Several industry responses indicated that a product that would meet the PLGR
requirement could be available by September 1991” (Ref. 32). Contract award was made to
Rockwell International, Collins Avionics and Communications Division, in March 1993. Table
3-9 describes the requirements of the PLGR compared to the Army requirements. Figure 3-20
provides a clear indication of the trend toward non-developmental items (NDI) in some areas of
GPS receivers.
Table 3-9. Army and PLGR Requirements (Ref. 32) System Description
Characteristic Winning Receiver Requirement
Size Less than 90 in3 Less than 125 in3
Weight Less than 4 pounds Less than 4 pounds
Power Less than 3 watts 3 Watts
Mean time between failure 18,500 hours 18,500 hours
69
http://dsp.dla.mil/documents/sd-2/appendix-c.htm
Battery life 10 hours 10 hours
Military-unique features Full selective availability Full anti-spoofing
Full selective availability
Full anti-spoofing
Type of operation Hand operated Hand operated
Position, velocity and time @
100 meters/sec, 2G acceleration 18 meters 18 meters
Time to first fix Less than 3 min. Less than 5 min.
Time to subsequent fix Less than 1 min. Less than 1 min.
Operating temperature -20o to +60oC -20o to +70oC
Service life 6 year performance/ reliability warranty 5 year performance and reliability
Unit cost $1,300 in base and first option years; $772 in last option year N/A
Figure 3-20. DoD of UE Family Tree Collins Manpack (Ref. 35)
3.7 Full Operational Capability
After starting out as a vague new idea to utilize the new space frontier for navigation after
the launch of Sputnik I, separate technology efforts and studies resulted in a functional baseline
being established in 1973 for a more accurate and reliable means of worldwide navigation. Nearly
20 years later on 17 April 1995, Air Force Space Command declared GPS fully operational. The
system would eventually accomplish one of the DoD’s major goals of consolidating suites of
military navigation systems.
The system was successfully “battle-tested” in the Persian Gulf War years before the
Initial Operational Capability (IOC) and proved the operational capability worthy of the program
visionaries from the late 1960s .
70
The JPO was able to successfully establish themselves as system integrators and
controller of the functional baseline. With the assistance of Aerospace Corporation, they were
able to conduct the necessary system trade studies to optimize the functional baseline as
enhanced requirements were identified and budgets changed. Using the baselined structured
signal as the key interface, a specification tree was established based upon the interface of those
signals with the three major segments. Through the well-honed interface control process, the JPO
was able to manage all the segment specifications and system integration. On the contractors’
side and many other supporting government agencies, domain expertise existed at all levels
which enabled personnel to see the system vision and perform their systems engineering process
with success. Communications was a key ingredient that was fostered throughout GPS
development.
71
4. SUMMARY
The GPS program presented challenges in various areas such as technology, customers,
organization, cost, and schedule for a very complex navigation system. This system has become
a beacon to military and civilian navigation and other unique applications. As best put by
Gedding, GPS provides “a constellation of lighthouses in the sky …” (Ref. 8).
Several precepts or foundations of the Global Positioning Satellite program are the rea-
sons for its success. These foundations are instructional for today’s programs because they are
thought-provoking to those who always seek insight into the program’s progress under scrutiny.
These foundations of past programs are, of course, not a complete set of necessary and sufficient
conditions. For the practitioner, the successful application of different systems engineering
processes is required throughout the continuum of a program, from the concept idea to the usage
and eventual disposal of the system. Experienced people applying sound systems engineering
principles, practices, processes, and tools are necessary every step of the way. Mr. Conley,
formerly of the GPS JPO, provided these words: “Systems engineering is hard work. It requires
knowledgeable people who have a vision of the program combined with an eye for detail.”
Systems engineering played a major role in the success of this program. The challenges
of integrating new technologies, identifying system requirements, incorporating a system of
systems approach, interfacing with a plethora of government and industry agencies, and dealing
with the lack of an operational user early in the program formation required a strong, efficient
systems engineering process. The GPS program imbedded systems engineering in their
knowledge-base, vision, and day-to-day practice to ensure proper identification of system
requirements. It also ensured the allocation of those requirements to the almost-autonomous
segment developments and beyond to the subcontractor/vendor level, the assessments of new
requirements, innovative test methods to verify design performance to the requirements, a solid
concept of operations/mission analysis, a cost-benefit analysis to defend the need for the
program, and a strong system integration process to identify and control the “hydra” of interfaces
that the program encountered. The program was able to avoid major risks by their acquisition
strategy, the use of trade studies, early testing of concept designs, a detailed knowledge of the
subject matter, and the vision of the program on both the government and contractor side.
72
5. QUESTIONS FOR THE STUDENT
The following questions are meant to challenge the reader and prepare for a case discussion.
Is this program start typical of an ARPA/ DARPA funded effort? Why or why not?
Have you experiences similar or wildly different aspects of a Joint Program?
What were some characteristics that should be modeled from the JPO?
Think about the staffing for the GPS JPO. How can this be described? Should it be
duplicated in today’s programs? Can it?
Was there anything extraordinary about the support for this program?
What risks were present throughout the GPS program. How were these handled?
Requirement management and stability is often cited as a central problem in DoD
acquisition. How was this program like, or dislike, most others?
Could the commercial aspects of the User Equipment be predicted or planned? Should the
COTS aspect be a strategy in other DoD programs, where appropriate? Why or why not?
73
6. REFERENCES
1. The Contribution of Navigation Technology Satellites to the Global Positioning System,
Naval Research Lab Washington DC, 28 Dec 1979, DTIC ADA080548, pages 5, 15
2. Application of the NAVSTAR to the Network Synchronization of the DCS (Defense
Communications System) Defense Communications Engineering Center Reston VA, 1
Mar 1987, DTIC ADA181457
3. Cost Analysis of Navy Acquisition Alternatives for the NAVSTAR Global positioning
System, Naval Postgraduate School, Monterey CA, Dec 19
82
ADA 125017
4. Command and Control Functions and organizational Structure Required to Support the
NAVSTAR/Global Positioning System, Naval Postgraduate School, Monterey CA, Jun
1980, ADB051422
5. Impact of NAVSTAR Global positioning System on military Plans for Navigation and
Positioning Fixing Systems, Institute for Defense Analyses Alexandria VA, Oct 1975,
ADB011137
6. Global Positioning System: Theory and Applications Vol I & Vol II, Edited by Bradford
W Parkinson and James J. Spilker, Volume 163 and 164, Progress in Astronautics and
Aeronautics.
7. FAA Acceptance Tests on the Navigation System Using Time and Ranging Global
positioning System Z-set Receiver, Federal Aviation Administration Technical Center,
Atlantic City, Airport, NJ 08405, Jul 1982, ADA119306
8. All in a Lifetime, Science in the Defense of Democracy, Ivan A. Getting, Vantage Press,
Copyright 1969.
9. Genesis of Satellite Navigation, William H Geier and George C. Weiffenbach, John
Hopkins APL Technical Digest, Vol 19 No1, 19
98
10. FAS Space Policy Project, Military, Space Programs, Transit
http://www.fas.org/spp/military/program/nav/transit.htm
11. An Overview of TRANSIT Development, Robert J. Danchik, John Hopkins APL
Technical Digest, Vol 19 No1, 1998
12. HQ USAF Program Management Directive for Satellite System for Precise Navigation,
19 Jul 72.
74
http://www.fas.org/spp/military/program/nav/transit.htm
13. Development Concept Paper, Number 133, NAVSTAR Global Positioning System 15
Apr 1974, Approved by Deputy Secretary of Defense 11 May 74.
14. Global Positioning System Control/User Segment System/Design Trade Study Report,
General Dynamics Corp, San Diego CA, 28 Feb 1974, AD921522
15. GPS Eyewitness: The Early Years, Bradford Parkinson, GPS World September 19
94
16. Report from the Guidance and Control Panel Working Group 04 on the Impact of Global
Positioning System on Guidance and Controls Systems Design for Military Aircraft Vol
I, Advisory Group for Aerospace Research and Development Sep 1979
17. Defense Standardization Program, SD-2 Buying Commercial & Non-developmental
Items: A Handbook, 1 April 1996, Appendix C – Case Study 1: The Precision
Lightweight GPS Receiver, http://dsp.dla.mil/documents/sd-2/appendix-c.htm
18. Retuning the GPS Constellation, 1999, Performance Analysis Working Group, Capt
Michael Violet, 2SOP/DOAS,
http://www.fas.org/spp/military/program/nav/gps.ppt#266,9,GPS Constellation History
19. Global Positioning System Control/User Segment System Design Trade Study Report
General Dynamics Corp, San Diego CA, 28 Feb 74, AD9211522 & AD9211523
20. Brad Parkinson, An Interview Conducted by Michael Geselowitz, Nov 2 1999, Interview
379, for the History of Electrical Engineering the Institute of Electrical and Electronics
Engineers, Inc. and the Rutgers, State University of New Jersey
(http://www.ieee.org/portal/cms_docs_iportals/iportals/aboutus/history_center/oral_histor
y/pdfs/Parkinson379 )
21. NAVSTAR, http://www.astronaux.com/Project/NAVSTAR.htm
22. NAVSTAR: Global Positioning System-10 Years Later, 10 Oct. 1983, Proceedings of the
IEEE Vol. 71, No. 10
23. TIMATION and GPS History, http://NCST-
www.NRL.Navy.mil/NCSTOrigin/TIMATION.html
24. DoD Directive 5160.51, 31 August 1971
25. Satellite Geodesy, http://www. NGS.NOAA.gov/PUBS-LIB/Geodesy 4
Layman/TR80003D.htm
26. Modernization of GPS: Plans, New Capabilities and Future Relationship to Galileo, Keith
McDonald, Journal of GPS, Vol. 1, No. 1, 1-17;
http://www.gmat.unsw.edu.au/wang/jgps/vlnl/vlnlpA
75
http://dsp.dla.mil/documents/sd-2/appendix-c.htm
http://www.ieee.org/portal/cms_docs_iportals/iportals/aboutus/history_center/oral_history/pdfs/Parkinson379
http://www.ieee.org/portal/cms_docs_iportals/iportals/aboutus/history_center/oral_history/pdfs/Parkinson379
http://www.astronaux.com/Project/NAVSTAR.htm
27. Central Pacific International Technology, http://www.cpit.com/en/history.html
28. SS-GPS-101B, System Specification for the NAVSTAR , Global Positioning System,
Phase I, 15 Apr 1974
29. Briefing Engineering and Integration Approach, No Date (~2001-2002), Col. Rick
Reaser, Deputy System Program Director (GPS)
30. Office of Secretary of Defense (OSD) Memo, The NAVSTAR GPS, 24 August 1979
31. Satellite Acquisition, Global Positioning System, GAO/NSIAD-8-209 BR, September
19
87
32. Defense Standardization Program, SD-2-Buying + Non-developmental Items: A
Handbook, 1 April 1996, Appendix C – Case Study 1: The Precision Lightweight GPS
Receiver; http://dsp.dla.mil/documents/sd-2/appendix-c.htm
33. NAVSTAR, Global Positioning System (GPS), User Equipment, Novella on DoD User
Equipment, 30 June 1996;
http://www.FAS.ORG/SPP/Military/Program/NAV/UEOVPR.htm
34. Presidential Directive/PD/NSC-42, Civil and Further National Space Policy, October 10
1978, http://www.globalsecurity.org/space/library/policy/national/nsc-42.htm
35. Dr. Gernot Winkler’s comments on the review of this draft report, 27 April 2007
36. NAVSTAR Global Positioning System (GPS) Navigation Technology System Segment
Management Plan, July 1975
37. Dick Schwartz’ comments on the review of this draft report, 22 April 2007
38. GOA/NSIAD-91-74, Should Be limited Until Receiver Reliability Problems Are
Resolved, Mar 19
91
Global Positioning System
39. Integrated Multiservice Test and Evaluation Management Plan for NAVSTAR GPS, Oct
1991, Change 2, 1 Jul 1993,
40. GPS Acquisition Program Baseline, NAVSTAR GPS, 8 Aug 2000
41. YEE-83-001, YEE Configuration Management Plan for NAVSTAR Global Positioning
System, 3 Feb 1983
42. NAVSTAR User Equipment Introduction, Sep 1996
http://www.navcen.uscg.gov/pubs/gps/gpsuser/gpsuser ,
76
http://www.cpit.com/en/history.html
http://www.fas.org/SPP/Military/Program/NAV/UEOVPR.htm
http://www.globalsecurity.org/space/library/policy/national/nsc-42.htm
43. ICD-GPS 209, 1 December 1983, Interface Control Document for the Control Station/Air
Force Satellite Control Facility Interfaces of the NAVSTAR GPS Operational Control
System Segment, Co tract F04701-80-0011, CII 793911, 8 May
84
44. YEN 78-312A, Technical Requirements Document for Phase III Space Segment of the
NAVSTAR Global Positioning System, 21 Nov 1979
45. https://gps.army.mil/gps/CustomContent/gps/ue/dagr.html
46. Wikipedia, http://en.wikipedia.org/wiki/Global Positioning System
47. The Institute of Navigation, Navigation Museum
http://www.ion.org/museum/item_view.cfm
48. http://www.fas.org/spp/military/program/nav/uenovpr.htm
49. Nuclear Detonation (NUDET) Detection System (NDS) Characterization Test Plan, Air
Force Material Command, Space and Missile System Center/CZ, NAVSTAR Program
Office, 1 December 1993
50. Kernco Inc website, http://www.kernco.com/index.php?page=cesium
51. Los Angeles Air Force Base website
http://www.losangeles.af.mil/smc/smc%20homepage/gpswing
77
https://gps.army.mil/gps/CustomContent/gps/ue/dagr.html
http://en.wikipedia.org/wiki/Global
http://www.ion.org/museum/item_view.cfm
http://www.fas.org/spp/military/program/nav/uenovpr.htm
http://www.kernco.com/index.php?page=cesium
78
7. LIST OF APPENDICES
Appendix 1 – Complete Friedman-Sage Matrix for GPS
Appendix 2 – Author Biographies
Appendix 3 – Interviews
Appendix 4 – Navigation Satellite Study
Appendix 5 – Rockwell’s GPS Block I design and development team org chart
Appendix 6 – GPS JPO Organization Chart
Appendix 7 – Operational Performance Requirements
p p y
1. Contractor Responsibility 2. Shared Responsibility 3. Government Responsib
A. A. Requirements
Definition and
Management
Contactors were responsible for the allocated
baseline.
Industry conducted trade studies in response
to JPO taskings.
The JPO defined the overall top
level. They controlled the satell
structure, overall error budget, a
reviewed and approved by the JP
B. B. Systems
Architecture and
Conceptual Design
For each segment, the contractor controlled the
system architecture within the segment.
The Air Force and contractor team jointly
developed the mechanization of the signal
structure and its implementation
The JPO established the basic ar
1960s Air Force studies accomp
validated by TRANSIT and TIM
architecture with a comprehensiv
controlled interfaces, designs an
C C. System and
Subsystem Detailed
Design and
Implementation
Each segment contractor developed their own
part II specs, the allocation to their vendors
(e.g. EE&G for atomic clocks) and
implementation of their own Systems
engineering process.
System level trade sponsored by the JPO
affected the segment designs and required
close coordination between the two parties
to reach closure. e.g. constellation change
from 21 to 18
Government intermittently invol
the ICWG process. Highlighted
requirements could cause increa
detailed designs/products were r
D. D. Systems
Integration and
Interface
The contractors were responsible for the ICDs
within there segment. Supported the ICWGs
for segment to segment ICDs.
Industry/government jointly developed the
interface physical and functional definition.
Incompatibilities were jointly resolved; risk
was balanced against the functional baseline
by the JPO
The JPO was Prime Systems Int
for the Interface Working Group
Configuration Control Board (C
and made final decisions on app
E. Validation and
Verification
Extensive laboratories and simulations were
employed for testing to verify integration of
components, subassemblies, and subsystems.
IBM with Rockwell simulator validated
upload, transmit and receive of signals at Cape
Canaveral.
Contractors developed test plans/procedures to
verify final product met the specified
requirements and conducted the testing in
accordance with these plans/procedures.
Joint board established with participation of
JPO, Aerospace Corporation, contractor,
and vendor to track and resolve issues
during qualification and acceptance testing.
The JPO was responsible for app
final testing to meet specificatio
validation using pseudolites on a
signal concept. JPO was respon
testing at Yuma Proving Ground
F. Deployment and Post
Deployment
Life and accuracy performance of the
constellation far exceeded the estimated design
life.
Constellation updates and enhancements
continue through the current program office
and industry team. Acquisition strategy for
replacement SVs using Block upgrades,
e.g. IIR, IIF and III
The Air Force established Falco
Control Center. GPS now unive
baseline. Commercial drove pot
G. Life Cycle Support Minimal contractor support after launch.
Software upgrades, orbit changes and response
to on-orbit failures. Maintenance and operator
TOs developed for CS
On going joint management of the
constellation
Satellite life and software upload
H. Risk Assessment and
Management
Risk planning and management was
disciplined and managed at the appropriate
responsibility level
The contractor government team decided
jointly on both types of risk solutions.
The program office was respons
trades
I. System and Program
Management
Fully cooperative to the program office
strategy. Although they were segment
contractors, they approach the design form a
system point of view. Contractors aligned
organization to parallel JPO organization for
improved communications.
Domain experts on the combined
government and industry team were present
in all the key positions
JPO provided the functional bas
and the mandate “to put 5 bomb
69
Appendix 2 – Author Biographies
PATRICK J. O’BRIEN
Mr. O’Brien is a retired Civil Servant and Systems Engineer employed by the University of
Dayton Research Institute (UDRI) as a Senior Research Engineer. He provides technical
expertise in the areas of cargo aircraft aerial delivery systems and systems engineering.
Experience/Employment Highlights:
• Senior Project Engineer to the Air Force Flight Research Laboratory, Wright-
Patterson Air Force Base, Ohio
o Aerial Delivery expertise on the C-17 aircraft airdrop and air-launch of
the DARPA Quick Reach FALCON Rocket program
• C-17 System Program Office Flight Systems Engineer (Acting), Technical
Lead Wright-Patterson Air Force Base, Ohio
• C-17 System Program Office Mission System Technical Lead, Wright-
Patterson Air Force Base, Ohio
• Lead Systems Integration Engineer the B-1B Conventional Mission Upgrade
Program (CMUP), Wright-Patterson Air Force Base, Ohio
• Chief Support Systems Engineer (CSSE) for the B-1B CMUP, Wright-Patterson
Air Force Base, Ohio
• CSSE for the National Aero-Space Plane (NASP) program, Wright-Patterson
Air Force Base, Ohio
• Technical Management Specialist for the Directorate of Support Systems
Engineering, Wright-Patterson Air Force Base, Ohio
• Senior Cargo Aerial Delivery Engineer and Group Leader, Air Transport Test
Loading Agency, Wright-Patterson Air Force Base, Ohio
• Chairman of the Joint Logistics Commander’s Joint Technical Airdrop Group,
Wright-Patterson Air Force Base, Ohio
• Principal Air Force System Command member to NATO Air Transport
Working Party
Honors/Awards:
• Outstanding Civilian Career Service Award, 2004
• Exemplary Civilian Service Award, 2004
• US Army Superior Civilian Service Award, 2003
• ASC/EN Outstanding Career Achievement Award, 2003
Education:
• B.S. Aero-Space Engineering, University of Notre Dame, 1971
JOHN M. GRIFFIN
John Griffin is President, Griffin Consulting, providing systems engineering and program
management services to large and mid sized aerospace firms. He provides corporate strategy
planning initiatives for company CEOs, reviews ongoing programs to assess progress and
recommend corrective actions, and participates as an integral member of problem solving teams.
He is active in numerous leading-edge technologies and advanced system development
programs.
Experience/Employment Highlights:
• Director of Engineering, Kelly Space and Technology, Inc, San Bernardino, CA
o Conceptual design process of a space launch platform
• Director, Development Planning, Aeronautical Systems Center, Wright-Patterson
Air Force Base, OH
• Chief Systems Engineer, Engineering Directorate
• Director of Engineering, B-2 Spirit Stealth Bomber, B-2 System Program Office
• Engineering leadership land management from inception through 1st flight
• Source Selection Authority for two source selections
• Chief engineer, F-15 Eagle Fighter
• Chief Airframe Engineer, F-16 Fighting Falcon
• Chief Airframe Engineer, Air Launched Cruise Missile
Honors/Awards:
• Two Meritorious Service Medals
• Distinguished Career Service Medal for his 37 years of achievement, 1997
• Pioneer of Stealth, 1998
• University of Detroit Mercy; Engineering Alumnus of the Year, 2002
. Education:
• University of Detroit, Detroit MI, 1964: Bachelor of Aeronautical Engineering
• Air Force Institute of Technology, WPAFB OH, 1968: MS of EE
• Massachusetts Institute of Technology, Cambridge MA, 1986: Senior Executive
Sloan Program
Affiliations:
• Founder (1993) and President (1993-1997), Western Ohio Chapter Senior
Executive Association.
• Co-founder (1995) & President (1996-1997), Defense Planning and Analysis
Society.
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Appendix 3 – Interviews
The company affiliation and positions are those held on the GPS during the timeframe of
the case study. Alphabetical list of interviews include:
1. Ron Beard, TIMATION Program Manager, NRL
2. John Berg, Aerospace Corporation, Control Segment Engineer
3. Rob Conley, Air Force, Test, Control Segment and Systems Engineering
4. Tom Donahue, Air Force, System Test Director Systems Engineering Division
5. Dr. Malcolm Currie, Office of Secretary of Defense, Director of DDR&E,
6. Don Duckro, Air Force, Space Vehicle Engineer
7. Sherman Francisco, IBM,
8. Hugo Frueholf, Rockwell, Chief Engineer, Block I
9. Stevie Gilbert, Air Force, Deputy System Program Director
10. John Gravitt, Air Force, Control Segment & Systems Engineering
11. Gaylord Green, Air Force, Air Force Chief of Space Vehicle & System Program Director
12. Jerry Holmes, Texas Instruments, User Equipment Engineering
13. Bill Kaneshiro, Air Force, Systems engineering
14. Geddi Krishnamurti, Rockwell Collins, Project Engineer thru Director of Navigation &
Mission Management Systems
15. Don Latterman, Air Force, Upper Stage Engineering & Chief Engineer
16. Russ Nakamura, Air Force, Control Segment Chief, Program Element Manager
17. Dr. Brad Parkinson, Air Force, System Program Director
18. Mike Paul, Air Force, Test Director and User Equipment Integrator
19. Ed Powers, Naval Research Laboratory & Naval Observatory
20. Preston Prouty, Aerospace Corporation, Control Segment Engineer
21. Rick Reaser, Air Force, Satellite Vehicle and Deputy Program Director
22. Jim Reynolds, Air Force, Systems Program Director
23. Doug Robertson, Air Force, Launch Program & Space Vehicle Manager
24. Joe Saad, Air Force, Division Chief User Equipment, Director System Effectiveness,
Manager Ground Systems
25. John Scheerer, Air Force, Director Systems engineering & previous Deputy of Space
Segment
26. Dick Schwartz, Rockwell, Program Director
27. Jess Sponable, Air Force, Space Vehicle, Launch Vehicle Interface
28. Tom Stansell, Magnavox, User Equipment Engineering
29. Phil Ward, Texas Instruments, User Equipment Engineering
30. Joe White, Naval Research Laboratory, Atomic Clocks
31. Dr. Gernot Winkler, Naval Observatory, Senior Executive Service
Appendix 4 – Navigation Satellite Study
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Appendix 5 – Rockwell’s GPS Block 1 Organization Chart
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Appendix 6 – GPS JPO Organization Chart
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Appendix 7 – Operational Performance Requirements
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