| Nimbus 4 | |
| Mission Type: | Weather satellite |
| Operator: | NASA |
| Cospar Id: | 1970-025A |
| Satcat: | 4362 |
| Mission Duration: | 10 years and 5 months |
| Manufacturer: | RCA Astrospace |
| Launch Mass: | [1] |
| Dimensions: | 3.7x |
| Launch Date: | UTC[2] |
| Launch Rocket: | Thorad-SLV2G Agena-D |
| Launch Site: | Vandenberg SLC-2E |
| Decay Date: | September 30, 1980[3] |
| Orbit Epoch: | April 8, 1970 |
| Orbit Reference: | Geocentric |
| Orbit Regime: | Low Earth |
| Orbit Periapsis: | 1092km (679miles) |
| Orbit Apoapsis: | 1108km (688miles) |
| Orbit Inclination: | 80.114° |
| Orbit Eccentricity: | 0.00107 |
| Orbit Period: | 107.2 minutes |
| Apsis: | gee |
| Programme: | Nimbus program |
| Previous Mission: | Nimbus 3 |
| Next Mission: | Nimbus 5 |
Nimbus 4 (also called Nimbus D) was a meteorological satellite. It was the fourth in a series of the Nimbus program.
Nimbus 4 was launched on April 8, 1970, by a Thor-Agena rocket from Vandenberg Air Force Base in Lompoc, California, United States. The spacecraft functioned nominally until September 30, 1980. The satellite orbited the Earth once every 1 hour and 47 minutes, at an inclination of 80°. Its perigee was 1092km (679miles) and its apogee was 1108km (688miles).[1]
The fourth in a series of second-generation meteorological research and development satellites, Nimbus 4 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 torus-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 3.7m (12.1feet) tall, 1.45m (04.76feet) in diameter at the base, and about 3m (10feet) 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 degree for all three axes (pitch, roll, yaw)
The primary experiments consisted of:
The spacecraft performed well until April 14, 1971, when attitude problems started. The experiments continued to operate on a limited time basis until September 30, 1980.[1]