The geostationary orbit concept was proposed by Arthur C. Clarke, a British author and scientist.  The geostationary orbit can be built by geosynchronous orbit with zero eccentricity. The inclination is either right to the equator or zero. These geostationary orbits can be used in many allocations like meteorology and communication. 

Geostationary Orbits

As we already mentioned above, the geostationary orbit has an inclination angle of  00 and an eccentricity of zero. This satellite is fixed above a point on earth’s equator. These orbits are classified by the longitude of the sub-satellite on the equator point. This orbit moves at a constant speed in its orbit as the earth rotates at a constant rate of angle. 

The geostationary orbit has an altitude of 36,000 kilometres and revolves at a speed similar to the rotation of the earth. These satellites observe and collect information over specific areas in a continuous manner. 

Properties of geostationary orbit

Now, we can discuss the most important properties or characteristics of geostationary orbits.

• Eccentricity

The geostationary orbit is circular in form, as the eccentricity value is equal to zero. This is because the orbit cannot move near or far away from earth. It helps to track forward and backward in the sky.

• Inclination

The angle of inclination of the geostationary orbit is  00. This allows the orbit to stay constant over the equator at all times. It makes it stationary with respect to the latitude of the earth.

• Orbital stability

The geostationary orbit has an altitude of 35,786 km, placed directly above the equator. Hence, the orbital speed is 3.07 kilometres per second (km/s). The orbital period is equal to 1,436 minutes to make a sidereal day. 

• Period

Every sidereal day, the satellite will return to the same fixed point above the earth’s surface. So, the orbital period is equal to one sidereal day. The geostationary orbit holds the same longitude over a long time. 

The orbital period is expressed as T,

T = 2  a3 /

Here, the orbital period (T ) is related to the semi-major axis of the orbit;

  is the gravitational parameter; and

A is the length of the semi-major axis of the geostationary orbit

Advantages of Geostationary Orbits

• Satellites can monitor for 24 hours in a continuous manner from a single fixed location on earth.

• The tracking does not require a ground station. 

• The number of satellites to monitor or track the earth would be less than expected. Three satellites are enough to cover most of the parts of the earth.

• There is no need for inter-satellite handoff.

• It helps in multi-point distribution and broadcasting.

• The greater height paves way for the large geographical coverage.

Disadvantages of Geostationary Orbits

• The geostationary orbit is located at the equator of the earth. The polar region tends to get less coverage or tracking.

• The geostationary orbits provide poor coverage over higher latitudes.

• The signal reception is weak, as the transmission distance is long. To overcome this, advanced signal processing algorithms and a good low noise amplifier is required. This obviously increases the cost of ground station instruments.

• There will be a signal travel delay of 120 ms in one direction. 

Applications of Geostationary Orbits

• Remote sensing

The satellites at the geostationary orbits are designed as remote sensing platforms. The geostationary orbits can monitor the earth from the same perspective at various intervals. This can be used to observe the weather conditions. The main disadvantage is the great distance to the earth, which leads to a decrease in spatial resolution.

• Communication

It is mainly used for communication purposes. The three satellites are placed in orbit to establish communication between the locations of the earth. It is due to the difference in curvature of the earth.

• The geostationary satellites are used to determine the shapes and dimensions of the earth.

• It is used in studying meteorites and cosmic radiation.

• It is used in forecasting weather.

Conclusion

Geostationary orbit is a motionless orbit, built by geosynchronous orbit with zero eccentricity and inclination angle of. There are many characteristics of geostationary orbits with constant values like orbital period, orbital stability, inclination, and eccentricity. It is helpful in communications, weather forecasting, and broadcasting. It holds both advantages and disadvantages. In recent times, low earth orbit is becoming popular, which has a simple design with non-directional antennas. This overcomes the disadvantages of geostationary orbits.