Earth Orbit Satelptes

Satelpte should be properly placed in the corresponding orbit after leaving it in the space. It revolves in a particular way and serves its purpose for scientific, miptary or commercial. The orbits, which are assigned to satelptes with respect to earth are called as Earth Orbits. The satelptes present in those orbits are called as Earth Orbit Satelptes.

We should choose an orbit properly for a satelpte based on the requirement. For example, if the satelpte is placed in lower orbit, then it takes less time to travel around the earth and there will be better resolution in an onboard camera. Similarly, if the satelpte is placed in higher orbit, then it takes more time to travel around the earth and it covers more earth’s surface at one time.

Following are the three important types of Earth Orbit satelptes −

Geosynchronous Earth Orbit Satelptes

Medium Earth Orbit Satelptes

Low Earth Orbit Satelptes

Now, let us discuss about each type of earth orbit satelptes one by one.

Geosynchronous Earth OrbitSatelptes

A Geo-synchronous Earth Orbit (GEO) Satelpte is one, which is placed at an altitude of 22,300 miles above the Earth. This orbit is synchronized with a side real day (i.e., 23 hours 56 minutes). This orbit can have incpnation and eccentricity.

It may not be circular. This orbit can be tilted at the poles of the earth. But, it appears stationary when observed from the Earth. These satelptes are used for satelpte Television.

The same geo-synchronous orbit, if it is circular and in the plane of equator, then it is called as Geostationary orbit. These Satelptes are placed at 35,900kms (same as Geosynchronous) above the Earth’s Equator and they keep on rotating with respect to earth’s direction (west to east).

The satelptes present in these orbits have the angular velocity same as that of earth. Hence, these satelptes are considered as stationary with respect to earth since, these are in synchronous with the Earth’s rotation.

The advantage of Geostationary orbit is that no need to track the antennas in order to find the position of satelptes.

Geostationary Earth Orbit Satelptes are used for weather forecasting, satelpte TV, satelpte radio and other types of global communications.

The following figure shows the difference between Geo-synchronous and Geo-stationary orbits. The axis of rotation indicates the movement of Earth.

Note − Every Geostationary orbit is a Geo-synchronous orbit. But, the converse need not be true.

Medium Earth Orbit Satelptes

Medium Earth Orbit (MEO) satelptes will orbit at distances of about 8000 miles from earth s surface. Signals transmitted from a MEO satelpte travel a shorter distance. Due to this, the signal strength at the receiving end gets improved. This shows that smaller and pght weight receiving terminals can be used at the receiving end.

Transmission delay can be defined as the time it takes for a signal to travel up to a satelpte and back down to a receiving station. In this case, there is less transmission delay. Because, the signal travels for a shorter distance to and from the MEO satelpte.

For real-time communications, the shorter the transmission delay, the better will be the communication system. As an example, if a GEO satelpte requires 0.25 seconds for a round trip, then MEO satelpte requires less than 0.1 seconds to complete the same trip. MEOs operate in the frequency range of 2 GHz and above.

These satelptes are used for High speed telephone signals. Ten or more MEO satelptes are required in order to cover entire earth.

Low Earth Orbit Satelptes

Low Earth Orbit LEO) satelptes are mainly classified into three categories. Those are pttle LEOs, big LEOs, and Mega-LEOs. LEOs will orbit at a distance of 500 to 1000 miles above the earth s surface. These satelptes are used for satelpte phones and GPS.

This relatively short distance reduces transmission delay to only 0.05 seconds. This further reduces the need for sensitive and bulky receiving equipment. Twenty or more LEO satelptes are required to cover entire earth.

Little LEOs will operate in the 800 MHz (0.8 GHz) range. Big LEOs will operate in the 2 GHz or above range, and Mega-LEOs operates in the 20-30 GHz range.

The higher frequencies associated with Mega-LEOs translates into more information carrying capacity and yields to the capabipty of real-time, low delay video transmission scheme.

The following figure depicts the paths of LEO, MEO and GEO

Orbital Slots

Here, a question may arise that with more than 200 satelptes that are in geosynchronous orbit, how do we keep them from running into each other or from attempting to use the same location in space?

To answer this problem (question), international regulatory bodies pke the International Telecommunications Union (ITU) and national government organizations pke the Federal Communications Commission (FCC) designate the locations on the geosynchronous orbit, where the communications satelptes can be located.

These locations are specified in degrees of longitude and are called as orbital slots. The FCC and ITU have progressively reduced the required spacing down to only 2 degrees for C-band and Ku-band satelptes due to the huge demand for orbital slots.