PAGEOS was a balloon satellite which was launched by NASA in June 1966. It was the first satellite specifically for use in geodetic surveying, or measuring the shape of the earth, by serving as a reflective and photographic tracking target. At the time, it improved on terrestrial triangulations of the globe by about an order of magnitude. The satellite, which carried no instrumentation, broke up between 1975 and 1976. One of the largest fragments of the satellite finally deorbited in 2016.

A balloon satellite, sometimes referred to as a "satelloon", is a satellite inflated with gas after it has been put into orbit.