Polar Orbit UPSC

Polar Orbit

• A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. 
• It therefore has an inclination of (or very close to) 90 degrees to the body's equator. 
• The Polar orbits are in a plane that is almost perpendicular to the plane of the equator and so passes over the poles of the Earth and then also, Earth rotates from East to West under the satellite. 
• A satellite in a polar orbit will pass over the equator at a different longitude on each of its orbits.
• For instance, if the period of the satellite is 6 hours then in one polar revolution, the earth will rotate around 90° westwards. Thus, in a couple of days, the whole earth can be mapped. 
• The Polar orbits are used for earth-mapping, earth observation, and reconnaissance satellites, as well as for some weather satellites. 
• However, Iridium satellite constellation also uses a polar orbit to provide telecommunications services.

Issues with Polar Orbits:

1. No one spot on the Earth's surface can be sensed continuously from a satellite in a polar orbit, this is its biggest drawback. 
2. The polar orbit can be manipulated also. 
3. If we want a satellite in polar orbit to remain to hover over a certain area for a larger time, it can be placed in a highly elliptical orbit with its apogee over that area.
4. The Polar Orbit is not much suitable for communication purposes because it moved in a different direction than that of the direction of earth's rotation.
5. So, the use of Polar satellites depends upon their arrival at a particular point on earth at a particular point. 
6. Near-polar orbiting satellites commonly choose a Sun-synchronous orbit, meaning that each successive orbital pass occurs at the same local time of day. 
7. This can be particularly important for applications such as remote sensing atmospheric temperature, where the most important thing to see is changes over time. 
8. The Polar orbits are also used for special applications like navigational satellites.