Geostationary orbit aka Geosynchronous equatorial orbit is a circular orbit that is located at 35,768 kilometers above the earth's equator and follows the direction of the planet’s rotation.
When any object is placed in the geostationary orbit, the orbital period of such an object becomes equal to the earth's rotational period which is one sidereal day. Because of this, it appears motionless to an observer on earth and is fixed in a position in the sky.
The concept of the geostationary orbits was popularized by fiction writer Arthur C. Clarke in the 1940s as a popular way to revolutionize telecommunication. In 1963, the first satellite was placed in a geostationary orbit.
The most commonly placed satellites in these geostationary orbits are the communication satellites. This is so that Earth satellite antennas located on the earth do not need to rotate to track them instead can permanently point at the position in the sky where the satellites are located.
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Uses of Geostationary Satellites
Geostationary Satellites find their uses in various fields. Some of them are mentioned below:
Geostationary communication satellites are used because they are visible from a large area of the Earth's surface which extends 81 degrees in both latitude and longitude. They are directly over the equator. To an observer near the pole, it appears lower in the sky. It removes the need for ground stations on the earth to have movable antennas which facilitate an observer to use small, cheap, stationary and directed towards the desired satellites.
These satellites are also used in meteorology. Geostationary meteorological satellites are used to provide infrared images of the Earth surface and atmosphere. They are used in oceanography and atmospheric tracking. These satellites capture images in the visual and infrared spectrum and help us track various weather phenomena like volcanic ash, cloud temperatures, oceanography, measuring temperature and vegetation coverage, cyclonic path, etc.
Navigation uses an augment system called the GNSS used for navigation purposes. This is used by relaying clocks, ephemeris and ionospheric error corrections. They provide an additional reference signal.
Properties of a Geosynchronous Orbit
The properties of a geo orbit are given below:
Inclination of geostationary earth orbit is zero which ensures that the inclination of the orbit remains over the equator always which makes it stationary for the ground observer.
The orbital time period of the geostationary orbit is equal to twenty-four hours or one Earth day. This implies that the satellite will return to its position after twenty-four hours irrespective of its other properties.
Eccentricity of the orbit of the geostationary orbit is zero because of it being completely round and this favors the fact that the satellites are at a fixed radius from the earth which helps in its tracing.
Geostationary Transfer Orbit
Geostationary Transfer Orbit is a special case of geocentric orbits which serves as an intermediate orbit for satellites that are destined for Geostationary orbit. It is an elliptical orbit with the perigee as low as the Low earth orbit and apogee as high as geostationary orbit. This is one of the Hohman transfer orbits. Usually, a geostationary satellite that is destined for geostationary orbit is first placed into a geostationary transfer orbit by its launching vehicle. The satellite uses its own engine to move from the geostationary transfer orbit to the geostationary orbit.
Geostationary orbits and geostationary satellites have emerged as subjects of rigorous research. These are extremely important for various activities taking place on the earth like navigation, weather forecasting, broadcasting, etc. These satellites also provide extremely essential data for intelligence. The study of these satellites are not only important but extremely interesting and finds popularity amongst the youth.
Did You Know?
How are Geo Satellites Launched?
This is a highly interesting procedure. Geostationary satellites when launched are directed eastward facing the prograde orbit which matches the equator’s rotation rate. Launching the satellite close to the equator provides the amount of inclination change needed later. The launching of the satellite close to the equator helps the earth's rotational force to give a boost to the satellite. While launching a satellite it is kept in mind that the east side has water or deserts so that in case of failure of the rockets, these rockets do not fall on any populated area. The majority of the vehicles to be launched in the stationary orbits are first directly launched into a stationary transfer orbit with the help of the vehicle. The geostationary transfer orbit acts as an intermediate orbit. The engine then provides propulsion force to raise it to a geostationary orbit.