Geostationary satellites are generally placed at an altitude of about 36,000 km. But polar satellites are generally positioned at an altitude of about 850 km, so that they circle the earth every 100 minutes or so.
The first polar satellite was launched on February 24, 1996 by national aeronautic and space administration (NASA). This was the second satellite to be launched under global geospace science project. TIDE/PSI investigation is an important function of the polar satellite.
The main purpose of a polar satellite is to collect information on radiation and other atmospheric dangers. When a satellite flies in the upper atmosphere, there are chances that the satellite’s instruments can be damaged by sun’s harmful radiation.
Polar satellites make use of both visible light and infrared (IR) radiations to make measurements of temperature and humidity in the earth’s atmosphere. Polar satellites also aid to record ground water and sea water temperatures, and monitor cloud cover and water/ice boundaries. Polar satellites are able to receive, measure, process, and retransmit data from balloons, buoys, and remote automatic stations distributed around the globe. These satellites may also carry search and rescue transponders to help locate downed airplanes or ships in distress.
Polar satellites make antarctic ozone level measurements, and long-term environmental measurements used to support global climate change studies. Polar satellites are also called low earth orbits (LEO). The polar satellite can view only the poles or a limited area on the earth at the same time. A special polar orbit that crosses the equator and each of the latitudes at the same time everyday is called a sun-synchronous orbit satellite.