What is the Station Keeping?
In order to keep stationary with respect to the earth and to stay in a well-defined position on the equator, orbit correction is needed. An orbit control system is employed to return the satellite to its correct orbit. The task deviation is referred to as station keeping. Accurate prediction of satellite position is required one or two weeks before and this requires skilled spaceman ship.
The principal task of station keeping is to sense satellite positioning parameters and provide corrective action if necessary. Various sensing devices such as radiation sensory device, gyroscope sensory device, and infrared sensors are installed on satellite board. But it is impossible to maintain the satellite absolutely immobile with respect to the earth hence a station-keeping box is defined.
Station-keeping in low Earth orbit:
For a rocket in a low orbit, the air drag is adequately solid to cause a re-entry before the proposed end of the mission if orbit raising moves are not executed every once in a while. A case of this is the International Space Station (ISS), which has an operational elevation over Earth's surface of somewhere in the range of 330 and 410 km. Because of environmental drag, the space station is continually losing orbital vitality. So as to make up for this misfortune, which would, in the long run, lead to reentry of the station, it has now and again been re-supported to a higher orbit. The picked orbital height is an exchange off between the normal push expected to balance the air drag and the delta-v expected to send payloads and individuals to the station. The upper impediment of orbit elevation is because of the imperatives forced by the Soyuz rocket. On 25 April 2008, the Automated Transfer Vehicle "Jules Verne" raised the orbit of the ISS out of the blue, accordingly demonstrating its capacity to supplant (and outflank) the Soyuz at this undertaking. GOCE which orbited at 255 km (later diminished to 235 km) utilized particle thrusters to give up to 20 mN of a push to adjust for the delay its frontal territory of around 1 m2.
Geostationary Orbit (GEO):
A geostationary orbit frequently alluded to as a geosynchronous tropical orbit (GEO), is a roundabout geosynchronous orbit 35,786 km (22,236 mi) over Earth's equator and following the heading of Earth's turn. An item in such an orbit seems unmoving, at a fixed position in the sky, to ground spectators. Interchanges satellites and climate satellites are frequently set in geostationary orbit, so the satellite receiving wires (situated on Earth) that speak with them don't need to turn to follow them, however, can be pointed for all time at the situation in the sky where the satellites are found. Utilizing this trademark, sea shading observing satellites with unmistakable and close infrared light sensors (for example GOCI) can likewise be worked in geostationary orbit so as to screen delicate changes of sea situations. A geostationary orbit is a specific sort of geosynchronous orbit, which has an orbital period equivalent to Earth's rotational period, or one sidereal day (23 hours, 56 minutes, 4 seconds). In this manner, the refinement is that, while an item in geosynchronous orbit comes back to a similar point in the sky in the meantime every day, an article in geostationary orbit never leaves that position. Geosynchronous orbits move around in respect to a point on Earth's surface in light of the fact that, while geostationary orbits have a tendency of 0° concerning the Equator, geosynchronous orbits have different tendencies and unconventionality.
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