How Do Geostationary Orbits Enable Global Communication?
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.
Concept of Geostationary
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:
Communication
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.
Meteorology
These satellites are also used in meteorology. Geostationary meteorological satellites are used to provide infrared images of the Earth's 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
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
The 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.
Time Period
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
The 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 serve 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 the 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 find 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.
A geostationary orbit is a high earth orbit that permits satellites to match Earth’s rotation. It is used for the purpose of broadcasting as ground station tracking is not needed. They are used in communication, weather forecast, etc.
Geostationary orbits are visible for 24 hours from the earth’s surface and since its position is fixed, it can record important events of the earth from its position. More about them have been explained in Geostationary Orbit - Geostationary Satellites, Uses, 'and Properties on the Vedantu website.
How To Make Notes on Geostationary Orbit?
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FAQs on Geostationary Orbit Explained: Uses, Properties & Applications
1. What exactly is a geostationary orbit in physics?
A geostationary orbit is a specific type of circular orbit located approximately 35,786 kilometres directly above the Earth's equator. A satellite placed in this orbit has an orbital period of exactly 24 hours, the same as the Earth's rotational period. Because it orbits in the same direction as the Earth's rotation (west to east), it appears to be stationary or fixed at a single point in the sky when viewed from the ground.
2. What are the essential conditions for a satellite to be in a geostationary orbit?
For a satellite to be truly geostationary, it must meet three precise conditions:
Orbital Period: It must have an orbital period of exactly 24 hours (one sidereal day) to match the Earth's rotation.
Orbital Plane: Its orbit must lie in the equatorial plane of the Earth, meaning it has an orbital inclination of zero degrees.
Altitude: It must maintain a constant altitude of approximately 35,786 km (about 22,236 miles) above the Earth's surface.
3. How is a geostationary orbit different from a geosynchronous orbit?
This is a common point of confusion. A geosynchronous orbit is any orbit with a period of 24 hours. A geostationary orbit is a special case of a geosynchronous orbit. The key difference is the inclination. While all geostationary orbits are geosynchronous, a geosynchronous orbit can be inclined. A satellite in an inclined geosynchronous orbit will appear to trace a figure-eight pattern in the sky, whereas a geostationary satellite (with zero inclination) remains fixed at one point.
4. What are the main applications and uses of geostationary satellites?
The fixed position of geostationary satellites makes them ideal for several critical applications:
Communications: Used extensively for telephone calls, television broadcasting (DTH services), and data communication, as ground-based antennas do not need to track them.
Weather Forecasting: They provide continuous monitoring of weather patterns and cloud formations over a large geographical area, enabling accurate meteorological predictions.
Broadcasting: Radio and television signals can be broadcasted over a vast region from a single satellite.
5. Why does a geostationary satellite appear stationary from Earth?
A geostationary satellite appears stationary because its orbital velocity and direction are perfectly synchronised with the Earth's rotation. It completes one full orbit around the Earth in the same amount of time it takes the Earth to rotate once on its axis (24 hours). Since it also travels in the same west-to-east direction and is positioned over the equator, it maintains the same relative position over a specific point on the Earth's surface.
6. What are the main advantages and limitations of using geostationary orbits?
Geostationary orbits offer significant advantages but also have key limitations:
Advantages: A single satellite can cover nearly one-third of the Earth's surface. Ground antennas can be fixed and do not require expensive tracking systems. They provide continuous, uninterrupted service for the area they cover.
Limitations: The high altitude causes a noticeable signal delay (latency) of about a quarter of a second for a round trip, affecting real-time applications like voice calls. They provide poor or no coverage for regions near the North and South Poles.
7. What would happen if a satellite had a 24-hour orbital period but was not over the equator?
If a satellite has a 24-hour orbital period but its orbit is inclined to the equator, it would be a geosynchronous satellite but not a geostationary one. From an observer's perspective on Earth, it would not appear fixed. Instead, it would trace a predictable, repeating path in the sky, typically a figure-eight shape known as an analemma, returning to the same point in the sky at the same time each day.
8. Can you provide some examples of Indian geostationary satellites?
Yes, India operates a large constellation of geostationary satellites. Prominent examples belong to the INSAT (Indian National Satellite System) and GSAT (Geosynchronous Satellite) series. These satellites are crucial for India's telecommunications network, DTH television broadcasting, weather forecasting, disaster warning systems, and satellite navigation services.
