State The Advantage of the same position of geostationary Satellites realative to surface of earth
Answers
One very popular orbit format is the geostationary satellite orbit. The geostationary orbit is used by many applications including direct broadcast as well as communications or relay systems.
The geostationary orbit has the advantage that the satellite remains in the same position throughout the day, and antennas can be directed towards the satellite and remain on track.
One particular form of geosynchronous orbit is known as a geostationary orbit. In this type of orbit the satellite rotates in the same direction as the rotation of the Earth and has an approximate 24 hour period. This means that it revolves at the same angular velocity as the Earth and in the same direction and therefore remains in the same position relative to the Earth.
In order to ensure that the satellite rotates at exactly the same speed as the Earth, it is necessary to clarify exactly what the time is for the rotation of the Earth. For most timekeeping applications, the Earth's rotation is measured relative to the Sun's mean position, and the rotation of the earth combined with the rotation around the Sun provide the length of time for a day. However this is not the exact rotation that we are interested in to give a geostationary orbit - the time required is just that for one rotation. This time period is known as a sidereal day and it is 23 hours 56 minutes and 4 seconds long.
Geometry dictates that the only way in which an orbit that rotates once per day can remain over exactly the same spot on the Earth's surface is that it moves in the same direction as the earth's rotation. Also it must not move north or south for any of its orbit. This can only occur if it remains over the equator.
Geostationary orbit can only be over the Equator
Geostationary orbit can only be over the Equator
Different orbits can be seen from the diagram. As all orbital planes need to pass through the geo-centre of the Earth, the two options available are shown. Even if both orbits rotate at the same speed as the Earth, the one labelled geosynchronous will move north of the equator for part of the day, and below for the other half - it will not be stationary. For a satellite to be stationary, it must be above the Equator.
Geostationary satellite drift
Even when satellites are placed into a geostationary orbit, there are several forces that can act on it to change its position slowly over time.
Factors including the earth's elliptical shape, the pull of the Sun and Moon and others act to increase the satellite orbital inclination. In particular the non-circular shape of the of the Earth around the Equator tends to draw the satellites towards two stable equilibrium points, one above the Indian Ocean and the other very roughly around the other side of the World.. This results in what is termed as an east-west libration or movement back and forth.
To overcome these movements, fuel is carried by the satellites to enable them to carry out "station-keeping" where the satellite is returned to its desired position. The period between station-keeping manoeuvres is determined by the allowable tolerance on the satellite which is mainly determined by the ground antenna beamwidth. This will mean that no re-adjustment of the antennas is required.
Assuming the shortest path length, this gives a single trip i.e. to the satellite or back of a minimum of around 120 milli-seconds. This means that the round trip from the ground to the satellite and back is roughly a quarter of a second.
Therefore to obtain a response in a conversation can take half a second as the signal must pass through the satellite twice - once on the outward journey to the remote listener, and then again with the response. This delay can make telephone conversations rather difficult when satellite links are used. It can also be seen when news reporters as using satellite links. When asked a question from the broadcasters studio, the reporter appears to take some time to answer. This delay is the reason why many long distance links use cables rather than satellites as the delays incurred are far less.
Advantages and disadvantages of geostationary orbit satellites
While the geostationary orbit is widely used for many satellite applications it is not suitable for all situations. There are several advantages and disadvantages to be taken into consideration:
Answer:
because the pole star perpendicular to the earth
Explanation:
geostationary satellites relatives of surface of earth
it is perpendicular to the earth