Major Components of a Satellite

Katrina G. / Physics 336 / 17 April 1997
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[ Gravity's Role ] [ Instrument Design ]
Satellites are complex machines which have intricate components and may be expensive. A satellite is any unmanned spacecraft projected from Earth with sufficient speed to coast out of reach of Earth's gravity to attain "escape velocity". Builders of satellites try to create an efficient satellite by making the parts more efficient and less expensive. Every part of a satellite plays an important role in launching it.

Components of a Satellite

There are many components in a satellite, such as the subsystems. Subsystems are groups of devices that help the instruments work together. There are many different kinds of subsystems, each with its own purpose. For example, command and data handling subsystems consist of computers that gather and process data from the instruments and execute commands from Earth. A power subsystem generates, stores, and distributes a satellite's electric power. This can include panels of solar cells that gather energy from the sun. Some things that help satellites work are a power supply and distribution system, telemetry, communications, and navigation system, on-board intelligence, and thermal management equipment. There are also different kinds of satellites which require different components to launch it. Some components needed in a multispectoral satellite are a scanner rotator, spherical focal point, focusing mirror, radiation gathering mirror, and a beam of radiation.

Engines in a Satellite

The engine is one of the most important parts of a satellite. A new "aerospike" engine was made with nozzles which have limited adaptability to pressure but work good in a vacuum. In some cases, payloads are needed. A payload can be a weapons system, optics, communications system,or scientific instruments. The payload cannot function without a satellite that supports it.

Cost of a Satellite

A lot of money is needed to make and launch a satellite. The price to launch a satellite sometimes depends on its size. A satellite being launched by TRW is a 20 foot tall model of the Earth Observing System satellite, complete with wing-like solar panel and cameras. Another is the half-size 67 foot prototype of Venture Star called X-33 which is supposed to be launched in 1999. However, no matter the size, satellites are expensive. Lockheed Satellite Company recently gave $1 billion for development of a satellite to the winner of a satellite design contest. However, without government grants, Lockheed Martin might not be willing to pay the $4 to $8 billion needed to launch the Venture Star. A new innovation by Lockheed Martin and NASA will shrink the shuttle's price-per-payload from $10,000 to $1,000, cut repairs and inspection costs, and reduce the time needed to build it. It is hard to launch an expensive satellite when hardly any contributions are made. Congress and the media seem not to be interested in space science and satellites, thus reducing public support for spending on space and satellites. Cassini comments on the subject, "I'm probably working on the last big spender among satellites--Cassini. That's more than $1 billion of development costs."

Reducing the Cost

There are new innovations that may reduce the cost of a satellite. The price has gone up. Goldin, a reporter, says, "Many people have aspirations of going into space; they should be able to afford to live those out". There are ways to reduce the cost, though. Small satellites and less expensive launch vehicles may reduce the cost of putting one into space. Designers of satellites push constantly to make them light and inexpensive.

Gravity's Role In Flying A Satellite

Certain conditions are needed in order for gravity to fly a satellite. For a satellite to orbit Earth, it has to be balanced inwards by gravity and outwards by centrifugal force. If a probe accelerated until its speed matched the planet it's orbiting, gravity can do the rest. Therefore, if a probe's speed is deliberately increased beyond seven miles/second, it will fly along an elliptical (egg shaped) path that can be directed out or inward from the Earth's orbit. However, the gravitational pull of a planet is very local and small so a space probe that passed close to it would not automatically be pulled into orbit. Satellites can also be used to measure the sun's damage. "The same space technology we've used to probe the other planets, to survey the moon and measure the sun's influences, can reveal the difficult process that shapes our environment.", says Tim Honnermann,Vice-President of TRW.

Instrument Design

Each instrument in a satellite needs to be tested thoroughly. Satellites' instruments are designed, built, and tested individually. Workers install parts on satellites one at a time. It is then tested under conditions that it will encounter in space. Satellites have to be tested especially before they are launched. Many satellites require minor adjustments of their orbit before they begin to perform and function. Once it is placed into stable orbit, it can remain for a long time without adjustment. Most satellites are launched by rockets that fall into the ocean after the fuel is spent.


Satellites have many complex components which have important functions. Through studying these components, we can better understand how satellites are launched. Also, satellites are very expensive. Many people are held back from satellite design and manufacture because they cannot afford it.


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