COBE
Cosmic Background Explorer

COBE is designed to look back to within one year of the Big Bang and help answer questions of fundamental importance to astronomy. COBE's observations of diffuse cosmic background radiation will help answer basic questions such as whether the matter in the universe is homogenously distributed, whether the universe is uniformly expanding and rotating, and how and when stars and galaxies first formed. COBE will also map interstellar and interplantetary 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 stabilizion (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 instument 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 emmitted from the primordial galaxies as they formed.

Country of Origin	United States
Customer/User	NASA
Manufacturer(s)	NASA Goddard Space Flight Center, Ball Space Systems
Size	5.49 m long, 2.44 m diameter
Orbit	887 x 898 km, incl. = 99.0 degree, sun synchronous
Design Life	1 year

Launch Facts

Name	Int'l Desig.	Date	Site	Vehicle	Orbit	Mass(kg)
Notes
COBE	1989-089A	11/18/89	WSMC	Delta 5920	LEO	2265
Cosmic Background Explorer; measured background galactic infrared radiation