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About Seasat

Seasat was a NASA oceanography experimental mission. It was launched on 28 June 1978 and ceased operations that same year. On board was the first-ever spaceborne synthetic aperture radar (SAR) system for science applications.

Mission Parameters
Orbit Altitude800 km
Orbit TypeNon-sun-synchronous, near-circular polar
Repeat Cycle17 days (sub-cycle of 3 days)

Seasat Objectives

Seasat had three main objectives:

  • To demonstrate techniques to monitor Earth's oceanographic phenomena and features from space on a global scale.
  • To provide timely oceanographic data to scientists studying marine phenomena, and to users of the oceans as a resource (ocean shippers, fishermen, marine geologists and others.
  • To determine the key features of an operational full-time ocean-monitoring system

Seasat Instruments

Synthetic Aperture Radar (SAR)

Seasat's SAR instrument provided spectacular images of Earth's land surfaces, thus demonstrating the immense potential of the SAR observation technology and generating great interest in satellite active microwave remote sensing.


Other instruments

Seasat carried five other instruments designed to return the maximum information from ocean surfaces:

SMMR (Scanning Multichannel Microwave Radiometer):
The SMMR was a five-frequency instrument of Nimbus-7 mission heritage. The instrument had the objectives of monitoring sea surface temperatures, wind speeds, rain rate, atmospheric water content (mapping of columnar water vapor distribution over the global oceans) and ice conditions. 

ALT (Radar Altimeter):
The ALT instrument was a Ku-band compressed pulse radar altimeter of S-193 heritage flown on Skylab and of ALT flown in the GEOS-3 mission. The instrument had the objectives of the determination of sea surface profiles, currents, wind speeds and wave heights. It was the first attempt to achieve 10 cm altitude precision from orbit.

SASS (Seasat-A Scatterometer System):
SASS (of S-193 heritage on Skylab) is a fan-beam dual-polarised Doppler scatterometer with the objective of radar backscatter measurements (sigma naught) over ocean surfaces for estimation of the wind field. The experimental SASS instrument first demonstrated the ability to accurately infer vector winds over the ocean's surface from a spaceborne platform

VIRR (Visible and Infrared Radiometer):
VIRR is a supporting instrument on Seasat (of SR heritage on NOAA-1) with the objective to provide images of visual reflection and thermal infrared emission from oceanic, coastal, and atmospheric features that might aid in interpreting the data from the other Seasat sensors (also some quantitative measurements of SST and cloud top height). 

LRR (Laser Retro-Reflector):
A device to support precision orbit determination for Seasat. 


SAR Instrument Parameters
Radar Center Frequency1.275 GHz (L-band)
System Bandwidth19 MHz (linear FM)
Pulse Duration33.4 µs
Antenna Dimensions10.74 m x 2.16 m
Ground Incidence Angle23º±3º cross track
No of Looks4
Swath Width100 km
Radar Wavelength23.5 cm
PRF1464-1640 Hz
PolarizationHorizontal transmit, horizontal receive (HH)
Antenna Look Angle20º from vertical (fixed)
Antenna Type1024-element passive microstrip based arrays antenna, linearly polarized
Pixel Size25 m x 25 m
Transmitted Peak Power1 kW

Seasat Data


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