Encyclopedia Astronautica
Seasat



seasat.jpg
Seasat
Credit: NASA
American earth resources radar satellite. One launch, 1978.06.27. Seasat was the first satellite designed for remote sensing of the Earth's oceans with synthetic aperture radar (SAR).

The mission was designed to demonstrate the feasibility of global satellite monitoring of oceanographic phenomena and to help determine the requirements for an operational ocean remote sensing satellite system. Specific objectives were to collect data on sea-surface winds, sea-surface temperatures, wave heights, internal waves, atmospheric water, sea ice features and ocean topography. The mission ended on October 10, 1978 due to a failure of the vehicle's electric power system. Although only approximately 42 hours of real time data was received, the mission demonstrated the feasibility of using microwave sensors to monitor ocean conditions, and laid the groundwork for future SAR missions.

The spacecraft utilized the Agena upper stage to provide satellite bus functions, including power, telemetry (S-band), attitude control, and command and control functions. A sensor package containing the mission's five experiments was attached to the Agena, as were the experiments' antenna systems. The vehicle was 3-axis stabilized using momentum wheels and horizon sensors. The vehicle was oriented with the SAR and other antennas remaining nadir pointing and the Agena rocket nozzle and solar panels zenith pointing.

The payload included:

  • Synthetic Aperture Radar (SAR) - used to image the ocean surface (wave patterns), polar ice caps, snow coverage, and coastal regions. The experiment operated at L-band (1.275 Ghz) with a 100 km swath, and provided 25 meter vertical resolution. The experiment used a 2.2 m x 10.7 m corporate feed antenna.
  • Radar Altimeter (ALT) - used to measure wave heights by measuring spacecraft altitude above the ocean surface. The experiment operated at Ku-band and had 10 cm vertical accuracy.
  • Seasat-A Satellite Scatterometer (SASS) - used to measure wind speed and direction. SASS operated at L-band (1.275 Ghz) and provided accuracies of +/- 2 m/s (speed) and 20 deg. (direction).
  • Scanning Multichannel Microwave Radiometer (SMMR) - used to measure surface wind speed (+/- 2 m/s), ocean surface temperature (+/- 2 deg C), atmospheric water vapor content, rain rate, and ice coverage. The experiment was passive, and operated at 6.6, 18, 37, 10.7 and 21 Ghz with a 600 km swath width.
  • Visible and IR Radiometer (VIRR) - used to identify cloud, land and water features (in support of the other instruments) and provide ocean thermal images. VIRR operated between 0.25-0.73 Ám and 10.5-12.5 Ám, and had a 1900 km swath width with an IFOV of 2-5 km.

Gross mass: 2,300 kg (5,000 lb).
Height: 21.00 m (68.00 ft).
First Launch: 1978.06.27.
Number: 1 .

More... - Chronology...


Associated Countries
See also
  • Atlas The Atlas rocket, originally developed as America's first ICBM, was the basis for most early American space exploration and was that country's most successful medium-lift commercial launch vehicle. It launched America's first astronaut into orbit; the first generations of spy satellites; the first lunar orbiters and landers; the first probes to Venus, Mars, Mercury, Jupiter, and Saturn; and was America's most successful commercial launcher of communications satellites. Its innovative stage-and-a-half and 'balloon tank' design provided the best dry-mass fraction of any launch vehicle ever built. It was retired in 2004 after 576 launches in a 47-year career. More...

Associated Launch Vehicles
  • Atlas The Atlas rocket, originally developed as America's first ICBM, was the basis for most early American space exploration and was that country's most successful medium-lift commercial launch vehicle. It launched America's first astronaut into orbit; the first generations of spy satellites; the first lunar orbiters and landers; the first probes to Venus, Mars, Mercury, Jupiter, and Saturn; and was America's most successful commercial launcher of communications satellites. Its innovative stage-and-a-half and 'balloon tank' design provided the best dry-mass fraction of any launch vehicle ever built. It was retired in 2004 after 576 launches in a 47-year career. More...
  • Atlas F American intercontinental ballistic missile. Final operational version of Atlas ICBM. Differed in guidance systems. Deployed as missiles from 1961 to 1966. After retirement, the ICBM's were refurbished and used for over thirty years as space launch vehicles. More...

Associated Manufacturers and Agencies
  • JPL American agency;manufacturer of rockets, spacecraft, and rocket engines. Jet Propulsion Laboratory, Pasadena, USA. More...
  • NASA American agency overseeing development of rockets and spacecraft. National Aeronautics and Space Administration, USA, USA. More...
  • Lockheed American manufacturer of rockets, spacecraft, and rocket engines. Lockheed Martin, Sunnyvale, CA, USA. More...
  • Ball American manufacturer of spacecraft. Ball Aerospace and Technology, Boulder, Colorado, USA. More...

Bibliography
  • McDowell, Jonathan, Jonathan's Space Home Page (launch records), Harvard University, 1997-present. Web Address when accessed: here.
  • JPL Mission and Spacecraft Library, Jet Propulsion Laboratory, 1997. Web Address when accessed: here.
  • Lockheed Martin Coporation, Atlas Family Fact Sheets, September 1998.. Web Address when accessed: here.
  • McDowell, Jonathan, Launch Log, October 1998. Web Address when accessed: here.

Associated Launch Sites
  • Vandenberg Vandenberg Air Force Base is located on the Central Coast of California about 240 km northwest of Los Angeles. It is used for launches of unmanned government and commercial satellites into polar orbit and intercontinental ballistic missile test launches toward the Kwajalein Atoll. More...
  • Vandenberg SLC3W Delta, Atlas launch complex. First designated LC1-1 and used to launch Atlas Agena B with Samos payloads. After Samos cancellation, rebuilt in 1963 to support launch of KH-4 Corona spysats atop Thor-Agena. Refurbished in 1973 to accomodate surplus Atlas ICBM's in space launch role. More...

Seasat Chronology


1978 June 27 - . 01:12 GMT - . Launch Site: Vandenberg. Launch Complex: Vandenberg SLC3W. LV Family: Atlas. Launch Vehicle: Atlas/Agena F/D. LV Configuration: Atlas F/Agena D 23F.
  • Seasat 1 - . Payload: Seasat A. Mass: 2,300 kg (5,000 lb). Nation: USA. Agency: NASA; JPL. Class: Earth. Type: Earth resources radar satellite. Spacecraft: Seasat. USAF Sat Cat: 10967 . COSPAR: 1978-064A. Apogee: 765 km (475 mi). Perigee: 761 km (472 mi). Inclination: 108.0000 deg. Period: 100.10 min. Summary: Oceanographic. Spacecraft engaged in practical applications and uses of space technology such as weather or communication (US Cat C)..

1978 October 10 - .
  • Seasat fails - . Nation: USA. Spacecraft: Seasat. Seasat was the first satellite designed for remote sensing of the Earth's oceans with synthetic aperture radar (SAR). The mission ended on October 10, 1978 due to a failure of the vehicle's electric power system. The suspicion exists that the satellite was intentionally shut off because the quality and nature of the results obtained alarmed the Pentagon.

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