What is a Polar Orbit?
A satellite in a polar orbit is the one that travels around the North and South Poles. These satellites are sent several hundred to several thousand miles above the surface of the Earth. They tend to circle around the Earth about 14 times a day.
These satellites orbit the Earth at the same speed as the Earth's rotation at the same latitude. This latitude is specifically 0º latitude, that is, the equator. Therefore, these geostationary satellites appear to be hovering in the same spot in the sky and over the same patch of ground all the times.
What is a Geostationary Orbit?
Geostationary orbits are also called geosynchronous or synchronous orbits. These orbits have the same orbital period as that of the Earth. If the geosynchronous orbit is circular and equatorial, then it will maintain the same position over the Earth.
A circular geostationary orbit distance from the Earth is about 42,164 km from the center of the Earth, or approximately 35,790 km above mean sea level.
What Determines the Geostationary Orbit?
By using gravitational force equations and knowing the mass of the Earth and the satellite, the geostationary orbit can be determined. You can do this by equating the centripetal force which holds the satellite in orbit with the gravitational force.
By putting in the extra constraint of the angular speed of the satellite in orbit should match with that of the Earth's rotational speed, the orbit distance is calculated. The formula is:
r = (µ / ɷ 2) ⅓
r = (µ / ɷ 2) ⅓
Who Developed the Concept of Geostationary Orbit?
The person who is credited for developing the geostationary orbit concept was a well-known science fiction author, Arthur C. Clarke. Many had pointed out that bodies which travel to a certain distance above the Earth on the equatorial plant remain motionless with respect to the Earth's surface.
However, the suggestion of permanent man-made satellites was given by Clarke, in an article that was published in 1945' Wireless World.
The first geosynchronous satellite was sent into orbit in 1963, and in the following year, the first geostationary satellite was sent. The orbit distance is in the plane with the equator, thus, these satellites can be sent in only one circle around the world. Therefore, the grounds of these satellites is very limited.
The number of geostationary satellites is very high, although they won't ever bump into one another. But a lot of precaution has to be taken so that their frequencies do not interfere with the satellites nearest to them.
Uses of Geostationary Orbits
The armed forces around the world use geostationary orbits for detection of rocket launches, keep track of alarm systems, and many other defense moves.
The geostationary orbit distance from the Earth's surface should be 35,786 km. Any closer, and the orbit will decay. If it is farther away, the satellite will escape the Earth's gravitational pull.