Satellite are man-made bodies which revolve around the earth or any other planet. A natural satellite is called moon and our planet earth has only one moon.The first man-made satellite, the Sputnik I, was sent into space by Soviet Union in 1957. Artificial satellites are blasted into space using rockets and space vehicles and they revolve around the earth indifferent internationally defined orbits. A rocket is a kind of spacecraft or missile that obtains thrust from a rocket engine to move forward at a very high speed by expelling its exhaust in the backward direction obeying Newton’s third law of motion.Satellites are fitted with many computer-controlled systems.
Satellites are launched in space for many useful purposes so they are of different types and sizes. For example, weather satellites, communication satellites, research satellites, navigation satellites, military satellites etc. They rotate around the earth in different orbits with different speeds depending upon the purpose for which they are launched. Satellites can be dived into different classes such as geostationary orbit satellites, low earth orbit satellites and polar orbit satellites etc.
According to a report, more than 70 satellites are launched in space every year in various orbits for useful purposes. They are disposed of when they are no longer needed or they complete their life. Satellites are never designed to be brought back down to the earth. These disposed of satellites are called space junk or space debris. There is a high risk of collisions between the functioning satellites due to this space junk and it is an alarming factor for the scientists to clear this mess from the upper space. If we stop launching satellites from now on, even then it can take a lot of time to free space from this junk.
Space junk is increasing every year and as a result the risk of the collisions for functioning satellite is increasing as well. Apart from the abandoned satellites, there are also many other small metal objects in space that are revolving around the earth and are a part of the space debris. European Space Agency (ESA) claims that about 22,000 lumps of metals having size bigger than that of a coffee mug are wandering in space and over 170 million metal pieces of size 1cm are also flying in space.
Although the research is in its early stage, scientists are working hard to clear this space rubbish and want to make space litter-free. There are some ideas under consideration to get rid of this space junk. Lasers can be used to destroy these metal pieces as well as harpoons or nets can be used to catch the pieces of junk to make space rubbish-free.
(The writer is Punjab University Physics Department Chairman and Member Syndicate on Associate Professor’s seat. He can be reached at: firstname.lastname@example.org)