Geostationary Satellites
 


A geostationary satellite is launched in such a way that it follows an orbit parallel to the equator and travels in the same direction as the earth's rotation with the same period of 24 hours. Thus, it appears stationary with respect to the earth surface. A satellite following a geostationary orbit always views the same area on the earth. Thus, it is possible to monitor continuously any location within the field of view of its sensor. A large area of the earth can also be covered by the satellite.

Satellites in the geostationary orbits are located at a high altitude of 36,000 km from the earth's surface. At this distance, only low resolution images are acquired. The geostationary orbits are commonly used by meteorological satellites. Currently, the available geostationary satellites are:

  • GMS (Geostationary Meteorological Satellites) (Japan), over the Asia-Pacific region (140oE)
    • The currently operating GMS satellite is the GMS 5, launched on 17 Mar 1995. It carries the Visible and IR Spin Scan Radiometer (VISSR), with a visible band at 0.5-0.75 µm (1.25 km resolution) and an IR band at 10.5-12.5 µm (5 km resolution). There is an extra infrared channel to measure atmospheric water-vapour distribution. The instrument acquires the full earth image at a repeat frequency of 30 minutes.
  • FY-2 (Fengyun-2) (China), over the Asia-Pacific region (105oE)
    • The first Chinese Geostationary meteorology satellite FY-2B was launched on 10 Jun 1997. The satellite is equipped with a visible and infrared spin scan radiometer (VISSR), a cloud coverage information system and a data collection and transmission system. The VISSR is a 3-channel instrument: the visible channel operating at 0.55-1.05 µm, the infrared (IR) channel at 10.5-12.5 µm and the water vapour (WV) channel at 6.2-7.6 µm. The resolution for the visible channel is 1.25 km while that of the IR and WV channels is 5 km. The VISSR obtains a full view image every 30 minutes. It provides daytime reflective radiation data of clouds and the earth surface in the visible channel, infrared radiation data day and night from clouds and the earth surface from the IR channel, and the water vapour content of the middle and upper atmosphere in the water vapour channel.
    • A second geostationary meteorological satellite FY-2C was launced on 25 Jun 2000. It is an improved version of the first FY-2B satellite.
  • INSAT (Indian National Satellite System) (India), A series of geostationary satellites for meteorological observation and telecommunication over India and the Indian Ocean.
  • GOES (Geostationary Operational Environmental Satellites) (USA), over the American continents (75oW and 135oW).
  • METEOSAT (Europeean Space Agency), over Europe and Africa (0oE).

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Please send comments/enquiries/suggestions about this tutorial to Dr. S. C. Liew at scliew@nus.edu.sg Copyright © CRISP, 2001