Raduga-1 8

At the end of the 1960s, the USSR had small Strela satellites in low orbit and Molniya satellites in highly elliptical orbits to ensure its military telecommunications. The USA prefer to use the geostationary orbit. The OKB-10 begins in 1970 the development of a geostationary telecommunication satellite, named Raduga, which would be complementary to Molniya. A model of Raduga satellite is launched in March 1974. In July 1974, a modified Molniya satellite, Molniya-1S, is launched into geostationary orbit to test transmissions. The first Raduga satellite is successfully launched on December 22, 1975, but operates only for three months. The Raduga satellites are accepted in operational service in December 1979, after five test flights. The KBPM begins in 1985 the studies for a modernized version, called Raduga-1. A first unit is launched in June 1989 then, after two additional test flights, the system is considered operational. It is also developed an improved version Raduga-1M, which flown since 2007. Two other units are launched in 2010 and in 2013, then the operation of Raduga is ended. Raduga and Raduga-1 are very similar and are built on the KAUR-3 platform. The Radugas have a length of 5.5m, a diameter of 2.5m. The Raduga-1 have a height of 7,5m. The Raduga have a guaranteed life of one year, and the Raduga-1 of three years. They have an 11D78 motor system. It is made up of two identical blocks including each one a tank containing the two propellants and two 11D444 engines of 0,4N of thrust. The Raduga are the first satellites in the world to be stabilized on a geostationary position. This system also allows them to change position in geostationary orbit. Electrical power is provided by two solar panels from NPO Kvant. The Raduga-1M satellites are not based on the KAUR-3 platform, but are derived from the civil Ekspress AM satellites. They have a mass of 2600kg and a life span of ten years.