What are Polar Orbits?

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Sep 8, 2022

Polar orbits are earth-centered orbit that passes through the north-south poles with an altitude of 200-1000 km above the earth’s surface and have an inclination of about 60-90 degrees above the earth’s equator. They are used for earth-mapping, reconnaissance, and weather satellite applications.

A satellite in a polar orbit completes around 15-20 orbits per day from the north to south poles which indicates that they move at an incredibly fast rate around the earth. As the satellite in a polar orbit, passes through a specific region multiple times throughout a day, repeated images of the same region can be taken in short intervals making the mapping of the earth very convenient over the polar and other subsequent regions which are useful for observations. By using 2-3 Satellites in the polar orbit, a particular earth strip can be observed continuously, without intervals in a more detailed manner.

For a satellite to remain in this orbit, it needs to travel at a speed of 17,500 miles per hour (7.8 kilometers per second). This speed which is required for a satellite to maintain its orbit around the earth is known as orbital velocity. 

If the satellite’s orbital velocity is higher than the optimal value, it faces the risk of flying out of orbit and into space, rendering the satellite out of bounds. Additionally, if the orbital velocity is kept too low, the satellite will be pulled back to earth due to gravity causing it to crash and burn. If correct orbital velocity is maintained the gravity of the earth balances the inertia of the satellite, pulling it down to the earth’s surface just enough to enable the satellite to traverse in its intended orbit. At higher altitudes, the speed required to keep a satellite in an orbit changes. The speed of the satellite in an orbit is inversely proportional to the altitude from the earth’s surface.

Key parameters of a Polar Orbit

Parameters

Polar Orbit Attributes

The altitude of Polar orbits From Earth

200kms - 1000kms

Orbital Velocity for a satellite in a Polar orbit

17,500 mph (7.8 km/s)

Orbits Completed in a Day for a Satellite

15-20 Orbits per day

Satellites Needed

2-3 for Continuous Coverage

Satellite Life

3-7 Years

Propagation Loss

Low

Network Complexity

Complex

Broadband Capability

Poor