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Letters: TIMATION Developer's Honor Draws Fire

Brad Parkinson and Richard Easton respond to the Inside GNSS news article on the first satellites to fly atomic clocks, Roger Easton and the origins of GPS

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EDITOR'S NOTE: On March 31, Inside GNSS published an online article," National Inventors Hall of Fame Inductees Include TIMATION Developer." It reported the induction of Roger Easton into the National Inventors Hall of Fame. We subsequently received a letter from Bradford Parkinson.

Roger Easton is a scientist, engineer, and inventor who had a long career at the U.S. Naval Research Laboratory, where he played a major part in a series of satellite programs, including TIMATION. In 2005, he received the National Medal of Technology from President George W. Bush.

Dr. Brad Parkinson was the first manager of the NAVSTAR GPS Joint Program Office. In 2003 he shared the Charles S. Draper Prize with Ivan A. Getting for his contributions to the creation of the Global Positioning System. In 2004 he was inducted into the National Inventors Hall of Fame. Dr. Parkinson is a member of the Inside GNSS editorial advisory council.

Due to the nature and specificity of Dr. Parkinson’s remarks, Inside GNSS offered Roger Easton and his son, Richard, the opportunity to reply to Dr. Parkinson’s letter.

Brad Parkinson's letter appears below. Richard Easton's response follows.

Bradford Parkinson
To the Editor:
I noticed your web site picked up on Roger Easton’s induction into the Inventors Hall of Fame. You may already recognize that the basis, as stated, is very inaccurate.

I know that it is the view of Roger and his son, but neither of them had any hand at all in the synthesis and development of GPS. Roger was not present at the “Lonely Halls” meeting of 1973, when we decided what GPS was to be. On the other hand, I have generally held my tongue on his exaggerated claims for the last 35 years.

In your position as editor of a leading GPS magazine, you should know the following:

A careful read of the patent (#3789409, application in 1970 - important date!) reveals the following:

1. His signal was not GPS (CDMA) and was not resistant to interference and was not amenable to multiple satellites on the same frequency— it would have been self jamming. Most of his patent is devoted to describing Side-Tone Ranging.

2. His method demanded an atomic clock at the user.

3. His method was obviously two dimensional (called for “Lines of Position”). Had he tried for more, his signal would have interfered with itself.

Obviously these are very fundamental distinctions.

Further, the Air Force 621B program had earlier studied and published a secret System Study (performed from 1964 to 1966) that examined all techniques for passive ranging and navigation using satellites. It examined the technique he later patented and pointed out his method was much less capable.

This was completed four years before his patent application (1970) and eight years before his patent was issued (1974). The USAF study was finally declassified in 1979 and is now available. It also highlighted the four-satellite (no user atomic clock) technique we actually used for GPS. In a later Air Force study, Easton’s signal was carefully evaluated and rejected as unsuitable. These studies and updates were available to me and were the real basis for GPS when we made the system design decisions.

Until recently, to avoid further acrimony, I have deliberately kept quietr than re-create the great DOD battles of the early 1970s. The USAF study authors, Woodford and Nakamura (of the Aerospace Corporation), deserve the real credit, rather than Roger Easton in being the first describers of the GPS technique. Unfortunately they were gone from the scene when we began actual system development. Easton never described nor advocated the system design we selected for GPS.

In fact, by the time Easton’s patent was issued, the Air Force had already flown (~ 1971-1972) prototype GPS receivers using the real GPS (CDMA ) signals at the WSMR and demonstrated five-meter, three-dimensional accuracy. These tests confirmed the preferred, four-satellite operation (eliminating the need for a user atomic clock) and were completed before we made the selection of CDMA, and four satellites in view for GPS (1973).

Roger Easton insists on ignoring all of this.

Finally Easton’s clock work wasn’t the prototype for anything. Both the USAF Woodford study of 1964-66 and NRL advocated atomic clocks in space. To their credit, NRL attempted to develop a space-hardened clocks.

NRL clocks and satellites, according to their reports, generally failed early with inconclusive results — they were definitely not space-hardened. Most had failures that prevented any quantitative data. When they briefly worked on-orbit they revealed that none of their devices had the stability that we required (by at least an order of magnitude). Again, this is according to their own published reports.

Rockwell Corporation (Under our JPO [NAVSTAR GPS Joint Program Office] direction) independently developed the first space-qualified clocks with absolutely no heritage from NRL. (Verify with Dick Schwartz and Hugo Freuhof who led the effort at RI) The Rockwell clocks were the only working devices on the first four GPS satellites, and were the essential, last key in gaining approval at DSARC II to proceed with full-scale development.

Thus, none of Easton’s technology (clocks, signals, system design, and satellites) were prototypes nor were they used in developing GPS.

I do not think anyone deserves the title of “inventor” of GPS. Like a typical bridge design, it is the accumulation of many pieces of technology. The earliest description of the GPS technique was by Woodford and Nakamura. I was indeed the chief architect, but I think the real credit should go to the many people who worked for me and made it happen.

View graphs and plans are easy compared to actually developing hardware. There are about 50 engineers and managers who were the real heroes. I have asked every significant engineer and manager who was involved with the building of GPS for their views. Every single one has agreed with the above narrative. Many of these heroes are included in the CC line [of the e-mail to Inside GNSS]

That said, there have been a number of significant, subsequent inventions regarding the use GPS for many things. Sadly, Roger Easton was not, to my knowledge, involved with any of them.

Finally, if there are doubters, they should read the patent and the Woodford Study, look at the dates, and form a judgment on this.

I am sending you this, not for myself, but for the rightful credit to those 50 people. (I would be glad to furnish you a list.) Easton seems intent on taking that from them. I have stood too long and listened to that and finally realized what he was doing.

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

Richard Easton


In his letter, Dr. Parkinson makes some assertions which are demonstrably incorrect. I encourage readers to study the patent and all other available documents from the years leading up to the building of GPS.

A thorough review of the literature shows that the GPS system, which the JPO designed and built (and for which Dr. Parkinson and all those who worked on the program deserve credit) evolved largely from the Timation program, whose fourth test satellite became the first NAVSTAR GPS satellite.

Dr. Parkinson asserts that Timation was a two-dimensional system. Many documents show that Timation was a three dimensional system. NRL’s Annotated Bibliography is an excellent resource and I will refer to it as AB in this letter.
(It’s available at <>.)

Page 73 of AB quotes a talk by Roger Easton at EASCON ’69 in which he states that Timation is a 3D system. Page 5 of AB quotes from the Timation Development Plan (1971), “Both range only and range-difference navigation provides continuous three-dimensional fixes (latitude, longitude, and altitude) over the entire globe.” Other pertinent quotes are at the bottom of page 50, on page 29, which shows the 3D mathematical formula and on pages 80-1.

Dr. John L. McLucas, who was Secretary of the Air Force from 1973-5, wrote on page 201 of Reflections of a Technocrat: Managing Defense, Air, and Space Programs during the Cold War: “In the late 1960s, both the Navy and the Air Force began work on improved three-dimensional navigation systems that would indicate altitude as well as latitude and longitude and work fast enough for use by aircraft. The Navy program was called Time Navigation (Timation for short).”

What evidence does Parkinson cite for Timation’s being 2D? His supposed evidence comes from patent 3789409, which has been called the key enabling patent for GPS. This is available on the web.
(For example: <>)

The figure on page one shows a ship with two satellites in sight. This provides a 2D position if the ship has an accurate synchronized clock. Parkinson believes that this is all Timation could do. But a simplification for purposes of illustrating passive ranging hardly demonstrates the maximum capability of the Timation system.

Note the statement on page 5: “Obviously many modifications and variations of the present invention are possible in the light of the above teachings. For example, the navigator’s station could obviously be on a flying airplane rather than on surface ship as described. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.”

Parkinson asserts that the Timation signals would have jammed themselves if an attempt was made to use them for 3D. However, the patent states that the carrier frequencies would be different.

Regardless of the results of the Woodford/Nakamura study cited by Dr. Parkinson, by the critical year of 1973 621B DID NOT use space-borne atomic clocks but was a repeater system in which time was sent from a ground station. This necessitated that the ground station controlling the European constellation be in Europe; this would have made the system far more vulnerable than Timation.

On April 17, 1973, Deputy Secretary of Defense (DEPSEC) William P. Clements issued a memorandum Defense Navigation Satellite Development Plan (DNSDP), stating that the Air Force would design and deploy during 1977 a constellation of four synchronous, repeater Navigation Experimental Satellites (NES). The DEPSEC further directed the Navy to launch Timation 3 in 1974 to be renamed Navigation Technology Satellite #1 (NTS-1).

After the Labor Day Conference in 1973, NTS-1 was launched but the NES satellites were canceled since the Timation mid-altitude constellation was selected.

Dr. Parkinson attacks the usefulness of the NTS-1 and 2 clocks. Again, the facts don’t support him. “A Historical Review of Atomic Frequency Standards Used in Space Systems” by Bhaskar, N.D.; White, J.; Mallette, L.A.; McClelland, T.A.; Hardy, J. [from Proceedings of the 1996 IEEE International Frequency Control Symposium] states:

“The NTS-1 & 2 clearly established the excellent improvement in frequency stability of AFSs [atomic frequency standards] over the XOs [quartz crystal oscillators] and also demonstrated the feasibility of producing AFSs for space applications. Each AFS in NTS-2 performed well in space for about eighteen months.”
< /xpl/freeabs_all.jsp?arnumber=559816> Note that Bob Kern and Art McCoubrey built the AFS in NTS-2.

The article then states: “The performance of the AFS in the first 3 Block 1 satellites was inferior to this. “The mean life of most of these AFSs was low (typically less than a year). The numerous early failures of these Rb AFSs raised a lot of concern regarding the reliability of these AFSs.”

Thus, the NTS-2 AFSs had good performance compared to the ones in the next three satellites. And the Navy has a long tradition of developing atomic clocks (see the timeline beginning on page 7 of AB). NTS-3 was scheduled to carry the first hydrogen maser, developed by NRL, into orbit, but it was canceled by the JPO in 1979.

There may have been valid cost reasons for this, but the fact remains that the NRL could have had a hydrogen maser in space more than two decades before Galileo did this. It’s not as if the NRL was negligent about clock development.

Memo 112, 9 June 1964, by Roger Easton already reflects many of the characteristics of GPS. It is printed in my Quest article, referenced below. Much work was done by the NRL prior to the patent being filed in 1970.

Space constraints prevent my answering at more length. I am working on a more detailed response to Dr. Parkinson’s statements and am already looking for a venue to publish it.

Additional resources are available at:

The Space Review <>

Quest: The History of Spaceflight Quarterly, Vol. 14 #3 <>

Spaceflight, February 2010, <>

Physics World, October 2007 <>

ION Newsletter, Winter 2007-8, p. 23 <>

High Frontier, Vol. 4 #3 < p 53-6>

GPS Inventor <>

Some good may come out of this dispute if Aerospace releases all its 621B documents to the general public.

Richard Easton
Chicago, Illinois

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