The Interball project was an international solar-terrestrial science program conducted by the Russian space agency in the second half of the 1990s. Interball-Tail (Interball-1), with an apogee of 200,000 km, perigee of 500 km, and inclination of ˜63¿ was targeted at studies of the solar wind, the magnetotail, and the outer magnetosphere. Interball-Auroral (Interball-2), with an apogee of 20,000 km and the same inclination, was targeted at studies of the inner magnetosphere and the auroral zone. Interball-Tail was launched on 3 August 1995 and entered the atmosphere in October 2000 in a fully functional state. Interball-Auroral was launched on 29 August 1996 and operated for 2.5 years. The Space Research Institute of the Russian Academy of Sciences was primarily responsible for the program. Sub-satellites provided by the Institute of Atmospheric Physics of the Czech Republic were detached from both Interball spacecraft shortly after the launch and remained within several thousands of km from the mother spacecraft throughout the flight.