|Mission type||Weather satellite|
|Mission duration||10 years and 5 months|
|Launch mass||619.6 kilograms (1,366 lb)|
|Dimensions||3.7 m × 1.5 m × 3.0 m (12.1 ft × 4.9 ft × 9.8 ft)|
|Start of mission|
|Launch date||April 8, 1970, 08:17UTC|
|Launch site||Vandenberg SLC-2E|
|End of mission|
|Last contact||September 30, 1980|
|Decay date||September 30, 1980|
|Perigee altitude||1,092 kilometers (679 mi)|
|Apogee altitude||1,108 kilometers (688 mi)|
|Epoch||April 8, 1970|
Nimbus 4 was launched on April 8, 1970, by a Thor-Agena rocket from Vandenberg Air Force Base, Lompoc, CA. The spacecraft functioned nominally until 30 Sep 1980. The satellite orbited the Earth once every 1 hour and 47 minutes, at an inclination of 80°. Its perigee was 1,092 kilometers (679 mi) and apogee was 1,108 kilometers (688 mi).
Nimbus 4, the fourth in a series of second-generation meteorological research and development satellites, was designed to serve as a stabilized, earth-oriented platform for the testing of advanced meteorological sensor systems, and for collecting meteorological data. The polar-orbiting spacecraft consisted of three major structures: a ring-shaped sensor mount, solar paddles, and the control system housing.
The solar paddles and the control system were connected to the sensor mount by a truss structure, giving the satellite the appearance of an ocean buoy. Nimbus 4 was nearly 3.7 metres (12 ft) tall, 1.45 metres (4.8 ft) in diameter at the base, and about 3 metres (9.8 ft) across with solar paddles extended. The torus-shaped sensor mount, which formed the satellite base, housed the electronics equipment and battery modules. The lower surface of the torus ring provided mounting space for sensors and telemetry antennas. An H-frame structure mounted within the center of the torus provided support for the larger experiments and tape recorders. Mounted on the control system housing, which was on top of the spacecraft, were Sun sensors, horizon scanners, gas nozzles for attitude control, and a command antenna. Use of an advanced attitude-control subsystem permitted the spacecraft's orientation to be controlled to within plus or minus 1 deg for all three axes (pitch, roll, and yaw). Primary experiments consisted of:
The spacecraft performed well until 14 April 1971, when attitude problems started. The experiments operated on a limited time basis after that time until 30 September 1980.