A body moving in an orbit around a
planet is called satellite. The moon is the natural satellite of the Earth. It
moves around the Earth once in 27.3 days in an approximate circular orbit of
radius 3.85 × 105 km. The first artificial satellite Sputnik was
launched in 1956. India launched its first satellite Aryabhatta on April 19,
Uses of satellites
(i) Satellite communication
Communication satellites are used
to send radio, television and telephone signals over long distances. These
satellites are fitted with devices which can receive signals from an Earth -
station and transmit them in different directions.
(ii) Weather monitoring
Weather satellites are used to
photograph clouds from space and measure the amount of heat reradiated from the
Earth. With this information scientists can make better forecasts about
weather. You might have seen the aerial
picture of our country taken by the satellites, which is shown daily in the
news bulletin on the television and in the news papers.
(iii) Remote sensing
Collecting of information about
an object without physical contact with the object is known as remote sensing.
Data collected by the remote sensing satellities can be used in agriculture,
forestry, drought assessment, estimation of crop yields, detection of potential
fishing zones, mapping and surveying.
(iv) Navigation satellites
These satellites help navigators
to guide their ships or planes in all kinds of weather.