Its scientific mission was to study in detail the sources of extra-terrestrial gamma radiation at energies above about 30 MeV.
The principal objectives were to study the spectrum and distribution of galactic gamma- rays, investigate the flux and distribution of extragalactic gamma-ray emission, investigate some known point sources in the gamma-ray range and search for new point sources.
The major results were the creation of the 2CG Catalogue that contained about 25 gamma-ray sources out of 30 observations made during the first three years. A binary system, Cygnus X-3 containing a pulsar and a gamma-ray emitter was thoroughly studied by COS-B. Two other enhanced objects, for which a lightcurve was compiled were the Crab and Vela sources. Furthermore, a first full gamma-ray map of the Galactic plane was made and the first gamma-ray AGN (active galactic nucleus) 3C 273 was detected. And finally, the spectrum of Geminga, one of the brightest gamma-ray sources in the compiled catalogue was derived to locate it to within 0.25 degrees permitting counterpart searches.
The originally foreseen duration of the mission was two years, but in fact Cos-B was finally switched off on 25 April 1982, having functioned successfully for 6 years and 8 months.During this time an extensive survey of the Galaxy was made in the energy range 50 MeV to 5 GeV.