Who invented the Global Positioning System?
by Richard Easton
|The Global Positioning System has revolutionized our society. Yet, there is disagreement over who created it.|
On February 13, 2006, my father, Roger Easton, received the 2004 National Medal of Technology from President Bush for “his extensive pioneering achievements in spacecraft tracking, navigation and timing technology that led to the development of the NAVSTAR-Global Positioning System (GPS).” The American Philosophical Society awarded the Magellanic Premium in 1997 to both Roger Easton and Bradford Parkinson. Their awards were worded identically, “for essential contributions to creating the Global Positioning System, thereby making the tools for precision navigation available to everyone.” In 1998, Roger Easton was inducted into the American Philosophical Society for his work on GPS. However, Easton was not mentioned in the American Heritage article nor was he cited by the National Inventors Hall of Fame.
So, which service’s technology is the basis of GPS? The evidence shows that GPS is essentially the Navy’s system, Timation, and does not use in any significant way the Air Force’s system, 621B. The clear evidence makes it astonishing that the opposite has been implied in articles.
Thus, senior editor Philip J Klass wrote on page 46 of the November 26, 1973 issue of Aviation Week and Space Technology:
The program also has been renamed the Global Positioning System to reflect better its principal mission for weapons delivery and the high accuracy potential of the system.
The ability of the USAF and Navy to resolve their long-standing differences over the orbital configuration by adopting basically the Navy-proposed constellation arrangements [emphasis mine] has eliminated one of the major obstacles to Pentagon approval for the program.
As Easton said in his acceptance speech for the Magellanic Premium, “On the Labor Day weekend, 1973, the Air Force accepted the Navy technology for satellite positioning, and here I salute Dr. Parkinson for knowing a good technology when he sees it.”
Parkinson’s assertion that Timation was two dimensional (latitude and longitude only) is wrong. It was three-dimensional. Thus, Klass wrote in the August 1973 Aviation Week article:
As additional Timation satellites are deployed, it becomes possible to make position determination on a three-dimensional basis (including altitude) on a more frequent basis.
Finally, with a total of 27 spacecraft deployed, a full 3-D continuously available position-fixing capability is provided.
|So, which service’s technology is the basis of GPS? The evidence shows that GPS is essentially the Navy’s system, Timation, and does not use in any significant way the Air Force’s system, 621B.|
Chester Kleczek, at the Bureau of Naval Weapons, was a strong supporter of Timation. He faced much opposition, as did Easton, from advocates of existing systems. At one point, an opponent from the Department of Defense commented that 43 navigation systems already existed. Kleczek asked which of them could give a Navy pilot his altitude in the South Pacific. None of these 43 systems could do this and so funding was obtained. Thus, an essential argument for Timation was its ability to give three positions. Parkinson’s comment that the Navy was only interested in two dimensions is silly in light of the importance of aircraft from aircraft carriers.
Further evidence of the Navy’s essential role in GPS comes from the Summer 1998 issue of the Institute of Navigation Newsletter:
Special recognition during the jubilee [75th anniversary of the Naval Research Lab] was given to Easton, an engineer at NRL for 37 years and the holder of basic patents relating to GPS. Easton worked on the design of 25 satellites while at NRL, according to an NRL information kit. In 1964, Easton put together the concept of using atomic clocks in satellites to fix the position of receivers listening passively to satellite transmissions, a one-way ranging technique that included a simplified method for interpreting the information received from the clocks. His 1964 concept was recognized in 1974 with U.S. patent 3789409 entitled “Navigation Systems Using Satellites and Passive Ranging Techniques.” Many persons deserve credit for making essential contributions to the development of GPS, but Easton’s filing is the enabling patent.
The basic configuration of Timation, 621B, and GPS is given in the table below. Clearly, GPS is Timation with a different signal. The interested reader can find many of the details in the August 1973 Aviation Week article by Klass.
|Number of satellites||27||3 or 4 groups of 5||24 satellites and 3 spares|
|Orbits||12,875 km (8 hour orbit, though the 12 hour orbit was also proposed)||Geosynchronous or near geosynchronous or high altitude circa 40,000 km||20,300 km, 12 hour orbits|
|Signal||sidetone range||Pseudo random sequence||Pseudo random sequence|
|Time setting on satellites||Atomic clocks on each satellite - periodic updates from ground stations||No clocks on satellites - time transmitted from seven ground stations||Atomic clocks on each satellite - periodic updates from ground stations|
A pioneer who had a similar idea to GPS should be mentioned. Roy Anderson, from General Electric, proposed to NASA in 1959 a satellite system for navigation using active receivers. It would have worked only when the sun was on the satellites. This probably reflected the primitive state of batteries at the time. However, this scientist deserves mention for being ahead of his time.
Parkinson has mentioned that a problem with Timation was that its signal, called side tone ranging (STR), was vulnerable to jamming. GPS uses pseudo random noise (PRN). It’s true that STR is slightly more vulnerable to jamming than PRN. However, it has the significant advantage that it produces a stronger signal. This would have mitigated the persisting problem that GPS does not work well in the woods or in houses with metal roofs. Parkinson agreed with Easton that they would use both systems; however, GPS only uses PRN.
One might ask why a group led by an Air Force colonel was given the responsibility to run a program using Navy technology. The Air Force was given the lead in space programs by the Department of Defense. Frank Ault, who was in charge of Transit and Timation, would have run GPS if the Air Force had not been given it. He very successfully ran Top Gun and doubtless would have done a good job on GPS.
Chester Kleczek, the Timation advocate mentioned earlier, deliberately did not ask about certain technical details of the system since he feared that others would claim credit for it. However, Mr. Kleczek says that the Russians became aware of it after the 1967 launch of the first test satellite and based their system, Glonass, on it. It would be interesting if experts on the Russian space program could confirm this.
|However, Project 621B played a major role in the development of GPS: not because of its technology, but because the Air Force was willing to fund GPS to an extent that the Navy and civilian agencies were not.|
Any large program like GPS depends on the work of many talented people. Two of Easton’s co-workers at the Naval Research Lab, James Buisson and Thomas McCaskill, ran a program on a mainframe to review different orbits and find the one which optimized the precision of the system. They arrived at a very precise answer that is still used today. Another co-worker, Don Lynch, calculated the relativistic shift that was important to synchronizing the time on the 24 satellites. Other important contributors at NRL included Charles A. Bartholomew and Randolph Zirn. An important outsider was Robert Kern; his firm manufactured the atomic clocks used by GPS satellites.
So what were the contributions of Parkinson and Getting to GPS? Parkinson deserves much credit for doing a good job of developing the program. Getting may have contributed to other important programs, but being a supporter of GPS does not make him an inventor of it. However, Project 621B played a major role in the development of GPS. Not because its technology was important for GPS; as I’ve proven, it wasn’t. In a telephone interview, Harry Sonneman, chairman of the Navigation Steering Committee at the Pentagon, commented that 621B pointed out to the Air Force the potential of a precision satellite-based navigation system. At the time, the projections were that the Air Force would lose many bombers in an attack on the Soviet Union. A precise navigation system could reduce these losses. In addition, the many failed attempts to knock out North Vietnamese bridges highlighted the need for more precise weapons systems. Thus, the Air Force was willing to fund GPS to an extent that the Navy and civilian agencies were not. However, GPS used primarily Timation’s technology as pointed out above.
Another advantage of Timation that both Klass and Sonneman mention is that it would provide useful information with as few as three satellites. 621B required at least four or five satellites for functionality, and no additional utility arises from 621B until the second cluster of satellites is complete, whereas Timation’s utility increases with each satellite from the third one onwards. In addition, the Navy tested some of the 621B orbits to obtain polar coverage and found them to be unstable. Considerable fuel would have been needed to maintain these orbits. Sonneman commented that one of the 621B satellite clusters would have been over the Soviet Union. This would have been a political nightmare as the Soviets doubtless would have claimed that they were spy satellites. Timation’s satellites, and GPS’s, orbit over the entire Earth and thus are not subject to this objection. In addition, Sonneman states that the ground stations, up to seven, needed for 621B would have been protested as were the ground stations for another contemporary system, Omega. Another disadvantage Sonneman mentions is that the close proximity of the 621B satellite clusters would have made them vulnerable to a single nuclear bomb or even conventional weapon attack.
Besides the signal, the sole potential advantage I found in the literature for 621B was that air surveillance of friendly forces and data communications could be added easily to the system.
The evidence shows that Roger Easton invented GPS and is finally getting credit for it as shown by his receiving the National Medal of Technology. Parkinson deserves much credit for his successful development of the system, but neither Parkinson nor Getting invented it. Further study about GPS has reinforced my prior understanding that the Navy had the technology and the Air Force had the money to fund it.