Minimum Speed of Satellite

Q. What is the minimum speed a satellite should maintain to revolve around Earth?

 

If you travel on Earth's surface, then the level seems to reduce 4.9 meters at every 7.9 Kilometers. The reason for that is Earth is round in shape. 

 

Keep this in mind, a simple calculation can give the answer: that is, the satellite should maintain a speed of 7.9 Kilometers per second or 28,440 Kilometers per hour to revolve around the lowest orbit of Earth.

Earth's gravity is 9.80665 m/s^2 (or 32.17405 ft/s^2). Earth's mass is 5.9891e24 kg (or 330,000,000,000,000,000,000 kg). In terms of acceleration, we have g = GM/r^2. Where G is the gravitational constant at 6.67384e-11 ^{m^3 kg^-1 s^-2}. M is the mass of the Earth at 5.9891e24 kg. And r is Earth's radius at 6.37640e6 m.

In simple terms, the speed of revolution is dependent upon the force of attraction that exists between the satellite and the earth. The greater the gravitational force, the faster the satellite will revolve around the earth.

There are two main types of orbits, elliptical and geosynchronous. The first one is those hotdog-shaped orbits, which are usually used for communication satellites. 

Most of them fly between 20,000 and 36,000 kilometers above the Earth's equator. Geosynchronous orbits are used for satellites that are designed for stationary observation. 

They fly around 35,000 kilometers above the Earth's equator. The satellites that are used for navigation, broadcasting, and weather observation are always in geosynchronous orbit. 

Since the earth rotates at a speed of approximately 1000 km/hour, the satellite flies at the above speed to make it appear stationary from the ground.