Letters to the Editor: Another View of GPS Origins

[Ed. Note: Mr. Beard’s letter has been significantly shortened — while trying to preserve its principal points and intent — to fit the space available in this print magazine. Here is a PDF of the full text of the letter and all accompanying footnotes. Scroll down for Brad Parkinson’s reply.]

The articles in the May and June issues of GPS World on the origins of GPS by Drs. Bradford Parkinson and Stephen Powers presented a detailed view of the people involved in the development of the GPS Program. This view on the origin of GPS essentially begins with the so-called “Lonely Halls” meeting where Dr. Parkinson and a group of Air Force officers invented the GPS concept that was subsequently developed by the teams of people discussed in some detail.

Missing from this view of the origin of the GPS concept are the developments and events leading up to the final decision on what was to have been the Defense Navigation Satellite System. The development, we are now expected to believe, originated from an Aerospace Corporation Study of 1964. The major events in the pre-history of the GPS program are not as well known as the events after the formation of the GPS program since, like the Aerospace study, they were classified and not generally available. Many of the documents of that pre-history have become declassified so that a more historical perspective can be made based on the actual documentation of events rather than subjective recollections of events.

Having worked during that era, I began as a naval officer assigned as the TIMATION project officer, Navigation Satellite Branch, Astronautics Division, Naval Air Systems Command, from 1968 to 1971. After separation from active duty I began working at the Naval Research Laboratory (NRL) in June 1971 in the TIMATION program, through the origination of the GPS Program, the Navigation Technology segment of the GPS program and became the head of the NRL Space Applications Branch in 1984 onwards. I believe I have a unique perspective on the origins of GPS, having participated from the Navy side. In the following I have attempted to describe the evolution of the TIMATION project and events leading up to establishing the GPS Program from the official Navy record.

It should be evident in this discussion that at the formation of the GPS Program, the TIMATION project ended, and the efforts following at NRL on NTS and space clock development were funded by the Navy as part of a Joint Program under the managerial direction of the GPS JPO. This relationship has been considerably de-emphasized and confused over the years, to the point where very few remember it.

The TIMATION project originated in FY 1965 as the Rapid NAVSAT Readout project under tasking by the Bureau of Naval Weapons. This Exploratory Development project was to investigate the feasibility of advanced navigation satellite techniques, among which was the concept of using passive ranging. The project included a number of experimental investigations into the concept of utilizing passive ranging based on precise time synchronization between a satellite and user receiver to produce more accurate and rapid positioning. An experimental satellite was developed and launched into low earth orbit for experiments in determining accurate satellite ephemerides and demonstrating a simplified technique for position fixing based on celestial navigation concepts. These techniques were intended to demonstrate, but were not limited to, two-dimensional positioning. Position fixing utilizing the celestial navigation plotting technique also determined the time offset of the clock in the user receiver so that it could be corrected for positioning or applied to time transfer techniques. An atomic clock was not required. A number of navigation and time transfer experiments were performed with this first satellite and data was collected for analysis of the concept. Another satellite was designed to incorporate the lessons learned from the first satellite and to perform other analytical studies. It was ultimately launched in 1969.

However, in 1968 the Joint Chiefs of Staff (JCS) formed a Navigation Requirements Panel to conduct a study, the results of which were approved on 24 September of that year. The new joint service navigation requirements established by this study included the ability of a user to precisely position themselves in three dimensions and precisely determine their velocity, continuously and worldwide. During the year following establishing of these new JCS requirements, the TIMATION project was expanded to address these new joint service navigation requirements.

Consequently, from 1968 through 1970 the TIMATION concept grew from a category 6.2 exploratory development project into navigation satellite techniques to a 6.3 advanced development system concept employing a constellation of medium altitude satellites containing space qualified atomic clocks to a worldwide distribution of various, surface and airborne, passive ranging user equipment. Technical design studies conducted were designed to analyze or experimentally demonstrate the technical aspects proposed to be selected for the DNSS. The specific technical areas that were investigated were: specific frequencies to be used, single or dual frequencies, and the propagation errors associated with their use; arrangement of the constellation of satellites, total number required for worldwide coverage and quality of coverage; ground stations necessary to operate the satellites and their location (foreign soil or U.S. territory); ranging signals to be used, the accuracy provided, resistance to countermeasures and vulnerability to such things as multipath reflections into a simple user antenna; and capability of being denied to the enemy.

The Navy and the Air Force 621B concepts were the two principal competing DNSS concepts for providing accurate three-dimensional navigational capabilities.

In 1970 the Astronautics Division of NAVAIR, sponsor of the TIMATION project, requested preparation of a system development plan to include a demonstration phase which could directly transition into an operational system. Such a plan was required for the Advanced Development phase (category 6.3 funding) of the project, which began with the establishment of the Advanced Development Objective (ADO) 34-11X, the requirements document for the project. The plan described the project requirements, approach, and objectives in some detail. In their guidance letter to NRL, NAVAIR provided guidance on the content of the development plan. The primary technical requirement for the effort was the “Precision navigation requirements in Phase I of the JCS Navigation Study approved 24 September 1968. — The most stringent requirement (being) user three dimensional position within the stated accuracies continuously on a global basis.”

[Ed: A detailed sequence of events, meetings, and memos excised here are fully viewable in this PDF.]

At NRL a GPS program office (Code 7907) was set up in March 1974 to coordinate GPS activities with the GPS JPO and manage NRL program activities. [ . . . .]

The development of space qualified atomic clocks at NRL, which had recommended and initially focused on cesium standards, began with the experimental rubidium standards on NTS-1. It was originally intended for experimentation with improved quartz crystal standards. The opportunity to include experimental rubidium clocks on NTS-1 presented itself some eight months before the satellite was completed. A new small rubidium frequency standard, model FRK, from Efratom of Munich became available and even though they were not specifically designed for space
their small compact size and design was attractive as a candidate space clock. Several of the FRK models were purchased from Munich, evaluated and modified for a space experiment in NTS-1. Two units were integrated into NTS- 1 and operated alternately with the primary quartz crystal standard. This same Efratom Model FRK was selected and proposed by Rockwell International for use in their Block I satellites. [. . . . ]

The clock development conducted and proposed by NRL was the subject of special program interest during these formative years. In February 1974 DDR&E in a memorandum to ASN (R&D) pointed out that “One of the most vital efforts in the recently approved NAVSTAR Global Positioning System (GPS) is clock development. Funds have been programmed under PE 63401N, NAVSTAR GPS, for programmatic developments defined in the DCP. However, there is a small, but important, effort which should be undertaken … I refer to the development of Space Qualified hydrogen maser clock and its correlative counterpart for the ground control station.” These funds mentioned and subsequent development efforts were Navy funds as part of the GPS joint development effort. The importance and emphasis on space qualified atomic clocks was highlighted in the DDR&E expansion of the GPS Phase I program to support the Submarine Launched Ballistic Missile Improved Accuracy Program. In that memo DDR&E called upon the Navy “to expand their NAVSTAR clock development effort. To reduce risk and provide timely NTS-2 support for the expanded satellite program the Navy should provide a second, parallel, cesium clock development, to be done by an aerospace contractor, for use on NTS-2. If either or both of the cesium clocks perform satisfactorily, cesium clocks should be used in any satellites subsequent to the initial six. The Navy NAVSTAR program should also provide in FY 1976 and beyond for (1) a hydrogen maser development for the NAVSTAR ground stations, and (2) efforts leading to a space qualified maser suitable for NTS-3 and future satellites.”

Considerable documentation and other material describing the extent and contributions to the GPS program resulting from the TIMATION development beginning in early 1974 could be further detailed. But in the interest of keeping this letter relatively brief those aspects will be covered elsewhere.

It should be evident in this discussion that the TIMATION project ended at the formation of the GPS Program. The subsequent NRL efforts on NTS and space clock development were funded by the Navy as part of a Joint Program under the managerial direction of the GPS JPO, however, many of the fundamental concepts and approaches began during the TIMATION program.

It is worthy to note as well, that over the years in addition to the recognition afforded Dr. Parkinson as the first program director of the GPS program, the contributions by Roger Easton and NRL have also been recognized. This recognition includes NRL being included as a major contributor to GPS in the Collier Award of 1992.

— Ronald L. Beard
Head, Space Applications Branch,
Space Systems Development Department,
U.S. Naval Research Laboratory,
Washington, D.C

Brad Parkinson replies:

I have great respect for Ron Beard and the many other fine engineers and spacecraft developers at NRL.

That said, I respectfully submit that the letter completely misses the point. There was a substantial amount of Pentagon infighting up to the time I took over the Program in late 1972. Ron has done a great job in documenting this cumbersome history. It accurately shows the paper trail from the NRL point of view. Dr. Currie reset the direction when he designated me to lead the Joint Program in 1973. The past assignments were essentially overtaken by that decision. There is another set of paper, that could be dredged out of the USAF files, but to little point.

The central issue is not paperwork. It is who conceived the concept, demonstrated the technique on the ground, and built the prototype system.

With a wave of the hands, NRL declares their system was also three-dimensional, yet the Easton patent clearly was not and the patent was clearly burdened with a militarily-
vulnerable signal structure. Apparently they disown their own preferred design. Yet, the patent is the clearest public record of NRL thinking.

The letter ignores:

• 
The first clear explanation of the tradeoffs between the various space navigation alternatives was the 621B “Woodford and Nakamura” study of 1964/66. It included the three-dimensional technique we selected in the final GPS design.
• The essential keys were: A. Single frequency transmission (CDMA) and B. Simultaneous ranging to four satellites. Both keys were conceived by 621B and demonstrated by the White Sands testing of real hardware (1970/1973). This became the basis for the GPS design in 1973. It is also the basis selected for all of the “copycat” systems by other countries (Russia has now announced a CDMA signal). NRL cannot point to any advocacy of such a system.
• 
NRL was indeed (as Ron points out) charged with clock development (but their spacecraft CDMA transmitter was provided by the JPO, not by NRL). Note that the early 621B study advocated atomic clocks in space for the system. NRL was not able to provide a useful space-borne clock until the fifth GPS prototype satellite. This was after the Rockwell/Efratom clock had become the only operational satellite clock used in the first four prototype satellites and after the GPS system testing had gained approval to proceed to full-scale development in 1980. Problems with the NRL test satellite precluded its inclusion in the test constellation.

It is correct that NRL advocated a MEO system, similar to the one we adopted for GPS. The Air Force’s 621B had wanted to demonstrate the four-dimensional technique using spacecraft, and launching the system a world-sector at a time. There are pros and cons both ways, but the controversy was both political and technical. The key to our selecting the GPS MEO constellation design was that it enabled the 4-6 satellite sub-constellation that was star (not solar) synchronized and that technique can be attributed to Major Gaylord Green of the Air Force. This allowed the extended testing on our well-instrumented range at Yuma Proving Ground.

In 1973/74, my problem was to find a way to advocate the right system without re-igniting the NRL/621B warfare. At that time, I chose to ignore most of the true 621B heritage of the JPO proposal and, in public, talk up the NRL contribution. A number of my colleagues in Aerospace and the old 621B were very perplexed with my behavior. I felt it was the right path to allow us to proceed with actually building the system.

I genuinely supported the NRL clock technology efforts, and was very disappointed when they were not able to meet our schedule. The space-qualified cesium clock, developed under NRL/Bob Kern, was a phenomenal accomplishment in spite of being late.

— Bradford W. Parkinson,
Edward C. Wells Professor of Aeronautics and Astronautics (Emeritus)
and Hansen Experimental Physics Laboratory
Stanford University, Stanford, California