The PAGEOS (Passive Geodetic Earth Orbiting Satellite) spacecraft was a 30.48 m inflatable sphere, and had no instrumentation on board. It was the second (following GEOS 1) NASA satellite in the National Geodetic Satellites Program.
PAGEOS 1 was made up of 84 gores and 2 pole caps of 0.0127-mm aluminized mylar film. The gores were 48 m long with maximum width of 1.24 m and the pole caps were 1.02 m in diameter. It was more or less a copy of the Echo 1 passive comsat. The primary purpose of the satellite was to provide a tracking target for geodetic purposes. It had a specular reflectance of 0.862, and a diffuse reflectance of 0.029, providing a reflecting light source whose brightness was relatively independent of observer-satellite-sun phase angle. The surface was also 97% reflectant for microwave energy in the range from 17 to 4E5 kHz.
The launch, orbit, separation, inflation and initial operation were nominal, with more than 40 ground stations participating in the observation program. The orbit was generally considered too high for drag-density study, although some work was done in this area by the Smithsonian Astrophysical Observatory.
PAGEOS operated for 9 years. It partly disintegrated in July 1975, which was followed by a second break-up that occurred in January 1976 resulting in the release of a large number of fragments. Most of these re-entered during the following decade. The last major fragment reentered on 2 September 2016.
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