Satellites are objects orbiting a planet. The moon is a natural satellite. Artificial satellites are those put into orbit by man.
The first artificial satellite was Sputnik I launched by the Soviet Union in 1957. Now almost fifty years later there are thousands of satellites orbiting the Earth at various heights.
There are various kinds of satellites. The satellites called communications satellites are used to relay telephone messages and radio and television signals. It is such satellites that have made it possible for us to see on TV, live, cricket and tennis matches being played in Europe or Australia. Formerly one had to wait till the next day to see the recorded version.
Some artificial satellites carry instruments that gather and send back information about the earth and its surroundings. This information is of immense value to weather forecasters, scientists, military planners and farmers and fishermen just to name a few.
A major effort is on to study the earth and all ecological changes taking place on earth through satellites. Satellites can provide ecologists with detailed images of every square metre of the earth's surface for study.
As there is no air in outer space and therefore no air resistance, satellites do not have to be sleek and streamlined, like rockets. So they come in a variety of shapes depending on the job they have to do.