This tutorial section on satellite basics covers following sub topics:
Main Page About satellite Bands Parts Orbits Services Types capacity allocations network configurations Applications Satellite TTC Remote sensing VSAT basics
The path around the Earth on which satellite revolves is called satellite orbit. To take care of gravitational pull of the Earth, satellite is launched with vertical as well as forward motion. Inertia produced by forward motion helps satellite move in a straight line. It requires speed of about 25000 mi/hour to break the gravitational pull by spacecraft, hence it is possible to put the spacecraft around the earth.
Satellite revolves around the earth either in a circular path or in
a elliptical path. In a circular orbit,height of the satellite is the distance from
the earth. When satellite is in elliptical orbit, two points are important.
One is the highest point called as apogee and lowest point called as perigee.
This apogee and perigee is measured from the geocenter of the earth and hence
earth's radius also to be taken into consideration.Satellite orbits are classified as below.
• Geostationary circular orbit- altitude of about 35786 Km and provides 24 Hr service on earth.
• Molnya orbit- This orbit is first used by Soviet union for Television transmission to its remote areas. Apogee is about 40000 Km and Perigee is about 1000 Km.
• Tundra Orbit- Apogee is about 46300 Km and perigee is about 25250 Km. Both Molnya and Tundra orbits are candidates for mobile satellite systems and for complementing the geostationary orbit in achieving better world wide coverage.
• Low earth circular orbit- It is at altitude of about 500-800 Km.Mainly used by radiometer. These are of use for earth resources, data relay and for navigation satellites as well as low cost store and forward communication systems.