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COS-B was the first European Space Research Organisation mission to study cosmic gamma ray sources. COS-B was first put forward by the European scientific community in the mid-1960s and approved by the ESRO council in 1969. The mission consisted of a satellite containing gamma-ray detectors, which was launched by NASA on behalf of the ESRO on August 9, 1975. The mission was completed on April 25, 1982, after the satellite had been operational for more than 6.5 years, four years longer than planned and had increased the amount of data on gamma rays by a factor of 25. Scientific results included the 2CG Catalogue listing around 25 gamma ray sources and a map of the Milky Way. The satellite also observed the X-ray binary Cygnus X-3.

Cos-B, a satellite to study cosmic gamma-rays
Mission typeAstronomy
COSPAR ID1975-072A
SATCAT no.08062
Start of mission
Launch date9 August 1975, 01:48:00 (1975-08-09UTC01:48Z) UTC
RocketDelta 2913
Launch siteSpace Launch Complex 2W, Vandenberg AFB, California
End of mission
Decay date18 January 1986 (1986-01-19)
Orbital parameters
Reference systemGeocentric
RegimeLow Earth


COS-B was launched from Vandenberg Air Force Base on August 9, 1975 on a Delta 2913 rocket.

The launch of COS-B from Vandenberg Air Force Base

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