Landsat 1

Infobox Earth satellite
name = Landsat 1


launch_date = July 23, 1972
launch_vehicle = Delta 900
launch_site = Vandenberg AFB
orbit_reference = WRS-1
orbit_type = nowrap|sun-synchronous, near-polar
orbit_altitude = 917 km (570 mi)
orbit_inclination = 99.2°
orbit_repeat = 18 days
orbit_swath = 185 km (115 mi)
orbit_crossing = 9:30 AM +/- 15 minutes

Landsat 1, originally named "Earth Resources Technology Satellite 1", was the first satellite of the United States' Landsat program. It was a modified version of the Nimbus 4 meteorological satellite and was launched on July 23 1972 by a Thor Delta rocket from Vandenburg Air Force Base in California. [cite web |url=http://history.nasa.gov/SP-4012/vol3/table1.33.htm |title=Chronology of Thor-Delta Development and Operations |publisher=NASA] The near-polar orbiting spacecraft served as a stabilized, Earth-oriented platform for obtaining information on agricultural and forestry resources, geology and mineral resources, hydrology and water resources, geography, cartography, environmental pollution, oceanography and marine resources, and meteorological phenomena.

To accomplish these objectives, the spacecraft was equipped with:
*a three-camera return-beam vidicon (RBV) to obtain visible light and near infrared photographic images of Earth;
*a four-channel multispectral scanner (MSS) to obtain radiometric images of Earth;
*a data collection system (DCS) to collect information from remote, individually equipped ground stations and to relay the data to central acquisition stations.

The satellite also carried two wide-band video tape recorders (WBVTR) capable of storing up to 30 minutes of scanner or camera data, giving the spacecraft's sensors a near-global coverage capability.

An advanced attitude control system consisting of horizon scanners, sun sensors, and a command antenna combined with a freon gas propulsion system permitted the spacecraft's orientation to be maintained within plus or minus 0.7 degrees in all three axes. Spacecraft communications included a command subsystem operating at 154.2 and 2106.4 MHz and a PCM narrow-band telemetry subsystem, operating at 2287.5 and 137.86 MHz, for spacecraft housekeeping, attitude, and sensor performance data. Video data from the three-camera RBV system was transmitted in both real-time and tape recorder modes at 2265.5 MHz, while information from the MSS was constrained to a 20 MHz radio-frequency bandwidth at 2229.5 MHz.

In 1976, Landsat 1 discovered a tiny uninhabited island 20 kilometers off the eastern coast of Canada. This island was thereafter designated Landsat Island after the satellite. As of 2006, it is the only island to be discovered via satellite imagery.

The spacecraft was turned off on January 6, 1978, when cumulative precession of the orbital plane caused the spacecraft to become overheated due to near-constant exposure to sunlight.

References