Prognoz was a series of Soviet research satellites meant to study processes of solar activity and their influence on the interplanetary environment and Earth's magnetosphere. Each spacecraft consists of a hermetically sealed cylindrical mainframe, 2 meters in diameter, with a spherical base. Inside the 0.925-meter-high mainframe is located the platform with instrumentation and equipment.
Twelve Prognoz satellites were launched between 1972 and 1996. Prognoz 11 and 12 were also known as the Interbol Tail Probe and Auroral Probe, respectively.