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. 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 1 was made up of 84 gores and 2 pole caps of 0.0127-mm aluminised 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. 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.