Seeking and investigating sources of gamma rays, the most energetic form of radiation, was the objective of COS-B, launched in 1975 by the European Space Agency. The mission ran until 1982. In April 1991, the Compton Gamma Ray Observatory set out to explore further, particularly to identify sources of mysterious gamma-ray bursts.
The Infrared Astronomical Satellite (IRAS), a joint mission of the United States, Britain, and the Netherlands, discovered more than 200,000 infrared sources during an all-sky survey of IR objects in 1983. It also found a class of galaxies ultraluminous at far-infrared wavelengths that may be dust-embedded quasars.