The Cosmic Background Explorer (COBE) satellite, under study by NASA since 1976, will map the spectrum and the angular distribution of diffuse radiation from the universe over the entire wavelength range from 1 micron to 1.3 cm. It carries three instruments: a set of differential microwave radiometers (DMR) at 23.5, 31.4, 53, and 90 GHz, a far infrared absolute spectrophotometer (FIRAS) covering 1 to 100 cm-1, and a diffuse infrared background experiment (DIRBE) covering 1 to 300 microns. They will use the ideal space environment, a one year lifetime, and standard instrument techniques to achieve orders of magnitude improvements in sensitivity and accuracy, providing a fundamental data base for cosmology. The instruments are united by common purpose as well as similar environmental and orbital requirements. The data from all three experiments will be analyzed together, to distinguish nearby sources of radiation from the cosmologically interesting diffuse background radiations. Con-struction is planned to begin in 1982 for a launch in 1988.