[1] It was the first satellite specifically launched for use in geodetic surveying,[3] or measuring the shape of the earth, by serving as a reflective and photographic tracking target.

Then, the balloon was inflated through a combination of residual internal air and a mixture of benzoic acid and anthraquinone placed inside, which turned to gas when the satellite was exposed to the heat of the sun.

[10] PAGEOS was placed into a polar orbit, about 200 nautical miles above the earth, so that the U.S. Coastal and Geodetic Survey could practically apply triangulation techniques developed from experiments with Echo 1.

[12] The PAGEOS spacecraft was launched by a Thor-SLV2A Agena-D (Thor 473) on 24 June 1966,[13][better source needed] and placed into a polar orbit (inclination 85–86°) with an initial height of 4200km,[14] which had gradually lowered during its 9 years of operation.

[citation needed] The satellite first partly disintegrated in July 1975,[10] which was followed by a second break-up that occurred in January 1976 resulting in the release of a large number of fragments.

[10] Thanks to its high orbit and its polar inclination, it did not pass through the Earth's shadow and was visible any time of night, unlike lower-orbit satellites which had to be viewed exclusively just before sunrise and after sunset.