New Moons Rising - GPS Declassified: From Smart Bombs to Smartphones - page 22

sand miles, and it is the oldest system for tracking the multitude of space
debris now in orbit. 123
The Space Surveillance system's continuous wave radar uses transmitters
and receivers placed hundreds of miles apart. To measure the wave accurately,
the receiver and transmitter must be precisely synchronized. Easton and his
associates first tried transmitting the time code over the horizon, but extrane-
ous noise introduced errors. Next, they carried an atomic clock by vehicle
between the stations. That worked better but created a time-consuming task
that had to be done continuously. In mid-1964 it occurred to Easton to put the
atomic clock in a satellite, where it could transfer precise time to the transmit-
ter and receiver simultaneously. 124 From there, using satellites with atomic
clocks to transmit time precisely enough for navigational purposes, especially
for the speeds associated with aircraft—something Transit could not do—
seemed to Easton a logical next step. But the idea was not immediately
embraced. “We were subjected to criticism because it was an idea looking for
an application and not the other way around,” Easton recalled in a November
2000 speech accepting a Distinguished Service Award at the Thirty-Second
Annual Precise Time and Time Interval Meeting. 125
If military leaders were not ready to launch atomic clocks into space, the
clocks themselves were not quite ready for the mission either. Much work
went into improving the accuracy of atomic clocks and “hardening” them to
withstand cosmic radiation. Technological advances were needed in other
fields, such as integrated circuits, which boosted the speed and shrank to a
portable size the receivers used to process satellite signals. Complex computer
simulations searched for the ideal altitude and arrangement of satellites to
keep at least four in view at all times everywhere, while using the fewest pos-
sible to reduce cost. Engineers differed over the types of signals that would
best transfer information from the satellites without being jammed. Funding
was a perennial issue.
Gradually, advocates of advanced satellite navigation became more numer-
ous, particularly in the Navy and the Air Force, and eventually at the Pentagon,
which in 1968 decided the military could afford only one such system. A com-
petition ensued, not unlike the one to launch the satellite for the International
Geophysical Year, but this contest remained mostly unnoticed by the public,
shrouded behind a cloak of military secrecy. That original competition persists
today in differing narratives about the origin of gps.
Subsequent chapters examine the competing claims, drawing on contem-