Types Of Meteorological Satellites

Meteorological satellites are of two types viz. Polar orbiting and Geostationary (Fig. 1). Polar orbiting satellites pass approximately over the poles at a height of about 850 kms. The whole surface of the earth is observable by these satellites which follow orbits nearly fixed in space while the earth is rotating beneath them. The areas scanned on each pass (swath) are nearly adjacent at the equator with overlapping areas further poleward. The swaths are usually about 2600 km wide. These satellites complete 14 orbits per day and thus can provide global coverage twice in 24 hours. Some of the polar orbiting satellites are NOAA, IRS, ERS-1 &ERS-2, TRMM(low inclination), DMSP, Oceansat-1 etc.

Geostationary satellites orbit around the earth over the equator at a height of about 36000 kms. They complete one orbit in 24 hours synchronised with earth's rotation about its own axis. Thus they remain over the same location on the equator. The main advantage of geostationary satellites lies in the high time-scale resolution of their data. A fresh image of the full earth's disc is available every 30 minutes. However they have limited spatial resolution as compared to the polar orbiting satellites in view of their distance from the earth. Useful information is restricted to the belt between 70 deg. N and south latitudes. Some of the examples of geostationary satellites are GMS( 1400 E ), GOES-W, GOES-E, INSAT-1 and INSAT-2 Series., GEOS, METEOSAT -5 (Positioned at 64 0 E ), METEOSAT-6 etc.

Figure 1 : Geostationary and Polar orbits
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