Traditional celestial navigation was accurate to +/- 400 meters, which
was more than adequate for the open ocean, but not for (say) aiming of
ballistic missiles. The PAGEOS project proved accurate to +/- 10 meters.

The doppler satellite program was accurate to about 5 meters, and the
present GPS system has evolved to centimeter accuracy.


The PAGEOS (Passive Geodetic Earth Orbiting Satellite) spacecraft was a
100'-diameter inflatable sphere made of aluminized plastic. As a
"balloon" it carried no instrumentation, and merely served as a
reflective tracking and photographic target. It was in a near-polar
orbit with an altitude of about 2600 miles. It was launched in 1966, and
in 1975 it broke up into many small pieces (some of these are still in
orbit, and useful for observing solar radiation pressure because of 
their extremely light weight).

Beginning in early 1969, the PAGEOS project occupied 40 worldwide sites,
including 4 in Antarctica--McMurdo, Mawson, Casey, and Palmer (the USCG 
icebreaker Southwind was also involved with establishing the site on
Heard Island). The goal was to take precisely timed photographs of the
satellite against the stellar background; comparing the data to
precisely determine the location of the stations. It used Wild BC-4
cameras which had previously been used with the more familiar ECHO 1A
and 2 satellites which had been launched in 1960 and 1964. The ECHO
satellites were about the same size as PAGEOS, but they were more
general-purpose (such as their use for much-publicized transcontinental
 telephone and TV tests) and had orbits only about half as high as
 PAGEOS, which was more specifically intended for geodetic experiments.

The project worked, but...it wasn't accurate enough for what folks
really wanted. Traditional celestial navigation was accurate to +/- 400
meters, which was more than adequate for the open ocean, but not for
(say) aiming of ballistic missiles. The PAGEOS project proved accurate
to +/- 10 meters. The doppler satellite program (which came next) was
accurate to about 5 meters, and the present GPS system has evolved to
centimeter accuracy.
PAGEOS was slow, since the photographic plates had to be sent in to the
headquarters office for processing. In addition, the system (unlike
celestial navigation) was not generally accessible to the common
user...that feature as well would have to wait for GPS.