The Cosmic Background Explorer was designed to answer questions of fundamental importance to astronomy. COBE's observations of diffuse cosmic background radiation helped answer basic questions such as whether the matter in the universe is homogeneously distributed, whether the universe is uniformly expanding and rotating, and how and when stars and galaxies first formed. COBE also mapped interstellar and interplanetary dust clouds. Originally planned for launch on the Shuttle, COBE was redesigned for launch aboard a Delta 2 following the Challenger disaster. COBE's supply of liquid helium was exhausted in September 1990, causing loss of the FIRAS instrument. Spacecraft: Spin stabilisation (0.8 rpm about sunline) using 3 reaction wheels, torque rods. Attitude control knowledge (4 arcmin) provided by magnetometers, earth sensors, sun sensors, gyros. Hexagonal spacecraft bus. Cryostat containing 95.7 kg of liquid helium for cooling sensors, protected against solar and terrestrial radiation provided by conical shield. Deployable solar panels provide 1050W BOL. Downlink through TDRSS. Payload: The instrument payload consists of the Differential Microwave Radiometer (DMR) to check the thermal and structural uniformity of the early Universe, the Far Infrared Absolute Spectrometer (FIRAS) and the Diffuse IR Background Experiment (DIRBE), to search for the remnant radiation emitted from the primordial galaxies as they formed.
Design Life: 1 year. Total Length: 5.5 m. Maximum Diameter: 2.4 m. Total Mass: 2,265 kg.
Cosmic Background Explorer; measured background galactic infrared radiation. Spacecraft engaged in research and exploration of the upper atmosphere or outer space (US Cat B).
The Cosmic Background Explorer's supply of liquid helium was exhausted, causing loss of the FIRAS (Far Infrared Absolute Spectrometer) instrument.