How do Satellites Work

Satellites are physical objects that are developed by humans and placed in Earth's orbit. They are commonly used for various scientific and technological purposes. Satellites have a number of instruments and subsystems to accomplish its mission. Basically, a subsystem is a set of devices that are responsible for carrying out the operations of the satellite, without any interruptions. The subsystems that are an integral part of any satellite, are described below:

Communications subsystem of satellites

The communication subsystem is the most vital part of a satellite. The key components of a communication subsystem are - antennas, receivers and transmitters. Their main function is to receive and send signals all across the globe. Some satellites and ground stations have specially designed radio dishes that are used for exchange of data. The curved section of these dishes helps in the reflection of both incoming as well as outgoing signals, from its central horn. The antennas are needed for the purpose of transmission of pictures at different frequency levels and with varying coverage. They are also capable of receiving instructions from Earth. The beacons and transponders fitted in some satellites, help in ground tracking.

Command and data handling subsystem of satellites

This subsystem comprises computers that collect all the data and process them on board. These computers are capable of delivering results according to the instructions received from the Earth. They are used for the physical measurement of distant objects. The inputs for this purpose are received from various sensory devices and processed to convert them into encoded data and the same is transmitted to the ground station for further analysis. This type of data transmission is a crucial task of satellites.

Power supply subsystem of satellites

The work of satellites is completely disrupted without the power supply subsystem. The main task of the power supply subsystem is to generate, store and supply adequate amounts of electrical power for the satellite. The power requirements of satellites depends on the total area covered by the satellite, kinds of instruments used and communication load.

There are various modes of power supply used by satellites. Satellites can use chemical batteries, solar cells or radioisotope devices. Solar cells are the most widely used in the power supply subsystem of satellites. Solar cells convert the solar energy into electrical energy. They are therefore the most reliable source of power supply. Chemical batteries oxidize the fuel for the production of power. They are used to supply electricity, when the satellite enters the shadow of the Earth. The disadvantage of batteries is their bulky size. For this reason, they are used mostly for short-term satellite missions.

Some of the the power supply subsystems are also provided with turbogenerators or thermionic generators. These generators use heat energy for producing electricity. The heat energy required is either obtained from the sun or from small nuclear reactors fitted with the subsystem. However, nuclear reactors have been used in satellites only on an experimental basis.

A satellite can work only when all these subsystems are performing their functions correctly. Malfunction in any of these subsystems can lead to total breakdown of the satellite.