A NASA satellite launched in 1989 November to map the cosmic microwave background (CMB). It carried three sets of instruments: a group of three Differential Microwave Radiometers (DMRs) to look for irregularities in the CMB; the Far-Infrared Absolute Spectrometer (FIRAS) to measure the spectrum of the CMB; and the Diffuse Infrared Background Experiment (DIRBE) to search for infrared radiation from forming galaxies. COBE’s most important results were the discovery of irregularities in the CMB on the level of 1 part in 105, and the confirmation that the spectrum of the CMB is a black body with a temperature of 2.73 K. Its observations ceased at the end of 1993.
http://lambda.gsfc.nasa.gov/product/cobe/ Official mission website.