Landsat 3

Description

LANDSAT 3 was a modified version of the Nimbus satellite, with the general mission objective of extending the period of space-data acquisition for earth resources initiated by LANDSAT 1 (formerly ERTS 1) and continued by LANDSAT 2. 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 two-camera return beam vidicon (RBV) and a five-channel multispectral scanner (MSS) to obtain both visible and IR photographic and radiometric images of the earth. A data collection system was also used to collect information from remote individually equipped ground stations and to relay the data to central acquisition stations. LANDSAT 3 carried two wide-band video tape recorders (WBVTR) capable of storing up to 30 min of scanner or camera data. 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 controlled to within plus or minus 1.0 deg 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 two-camera RBV system were transmitted in both real time and from the wide-band recorder system at 2265.5 MHz, while information from the MSS was constrained to a 20-MHz rf bandwidth at 2229.5 MHz.