Starshine 3's main task was to study the density of the Earth's upper atmosphere.

In addition, the 94 centimetres (37 in) and 91 kilograms (201 lb) heavy spherical satellite body was covered with 1,500 mirrors, which were manufactured by machine technology students in Utah and polished by almost 40,000 students in 1,000 different schools.

Students measured the difference in the daily shortening orbital period and derived the density of the atmosphere.

They also measured fluctuations in the intensity of UV radiation from the Sun, which they associated with different densities in the atmosphere.

Starshine 3 burned up on January 21, 2003 after 7,434 orbits in the Earth's atmosphere about two years earlier than originally expected.