Introduction to Satellites
Satellites are artificial objects that revolve around Earth. They are used for studying Earth for meteorological purposes, communication, entertainment (TV), resource management, disaster management, astronomy, space research, etc. One of the popular examples is the GPS system, which is based on a cluster of Satellites orbiting the Earth.
The orbit of a Satellite is the path that it follows when it revolves around the Earth. Satellites in circular orbits can be classified on the basis of the height above Earth. Closest to Earth is the Low Earth Orbit (LEO) with height of about 1000km. Most student Satellites are launched in LEO. Farthest from Earth is the Geostationary Earth Orbit (GEO) which is at the height of 36000km. (Radius of Earth is 6400km, hence GEO is about 6 times the radius of Earth!) Communication Satellites are usually launched in GEO.
Satellites also come in various sizes and shapes, depending on their mission. Communication Satellites are within half ton to a few tons in weight. Whereas, Student Satellites are usually between 1kg to 15kgs in weight.
A Satellite is a pretty complex system, and is made up of several Sub-Systems. They are:
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Payload Sub-system
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Communication Sub-system
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Controls Sub-system
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Power Sub-system
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Thermals Sub-system
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Structures Sub-system
The Power Sub-System which supplies power is like the heart of the Satellite. The Attitude Determination and Controls Sub-System ‘senses’ the surroundings and ‘moves’ the Satellite. (Attitude means orientation of the Satellite in space!). The Thermals Sub-System has to maintain the temperature of the Satellite. The Communication Sub-System helps the Satellite communicate with the people on Earth. Finally, all the ‘parts’ are housed in a strong ‘body’ designed by the Structures Sub-System so that it can survive safely in the harsh climate of space. The Payload Sub-System decides the mission of the Satellite. The On Board Computer, which helps all the other Sub-Systems by performing all the calculations and decision making jobs, is like the brain. All the Sub-Systems of a Satellite have to work together to make a successful Satellite.
In this virtual laboratory, we offer you experiments in three of these Sub-Systems which will enable you to understand the behavior of Satellites.
