Success Has Many Fathers - GPS Declassified: From Smart Bombs to Smartphones - page 43

Fig. 3.4. Capt. David C. Holmes at the
U.S. Naval Academy in 1943. (Cour-
tesy U.S. Naval Academy)
Peter Wilhelm, currently director of the Naval Center for Space Technology
at nrl, worked in the Satellite Techniques Branch under Martin Votaw when he
joined nrl in 1959. Wilhelm helped build the first electronic intelligence satel-
lite, named grab. His first project for Roger Easton was building satellites to
calibrate Space Surveillance. They were given the name surcal. Wilhelm asked
if there should be an off switch for the signal, but Easton did not think it was nec-
essary. The launch of surcal 1 was unsuccessful, but surcal 2 was launched
in December 1962, and it jammed the system for about ten seconds on each
orbit as its powerful transmitter overwhelmed the Space Surveillance system.
Wilhelm said that it was a big irritant until it burned up three years later. 15
The Timation (short for time navigation) program began in 1964. There is
some uncertainty about the sequence of events that year. Synchronizing Space
Surveillance's clocks in transmitter and receiver stations was critical for pre-
cisely obtaining the distance to a satellite being tracked. The tracking process
relies on measuring the time it takes radio signals to travel from the transmit-
ter to a satellite and be reflected back to receiving stations. If the clocks are
not synchronized, an error is introduced. Since radio signals travel at the speed
of light—299,792,458 meters per second—an error of one millionth of a second
(1 x 10 - 6 ) translates to an error of almost 300 meters. Easton recalled that in
September 1964 he conceived using a clock in a satellite to synchronize the