Tireless Servants in the Sky The space crafts that move in an orbit around the earth are called artificial satellites. Most satellites go around the earth once in about 90 minutes at a height of a few hundred kilometres. But it is possible to launch satellites with a proper speed at greater heights (around 36,000 kms). They would then move around the earth once in 24 hours and As our own INSAT series of satelites are geostationary ,satelites Every night towards thc end of Tv news on my channel. we are shown plctures of Clouds over UK. These pictures are laken by INSAT to earth, Apart from monltofing the weather, INSAT satellites are used to telephone calls. Television Progmmmes He also via these satellites. satellites carry equipment 10 survey the earth's natural resources and monitor weather. India's satellite Programme has also provided useful information on agricultural land and prospecting for ores and minerals. Recently, the satellite IRS 2D in the IRS (Indian Remote Sensing Satellite) series has been launched to smrey India's natural resources by remote sensing methods. The effect of living in space on plants and animals is also studied in satellites.
At present, Russia has a space station called Mir going round the earth as a satellite. Crew members and supplies are regularly sent to misstation where three or:more personswork at time, for periods as long as a year.
Satellites can pinpoint sources of pollution, spot forest fires and locate areas of disease in crops and forests. Weather conditions can be monitored by satellites enabling us to predict storms and prevent damage. Satellites also help in locating and guiding ships. But-the maximum use of satellites is made for communications. Space Probes-Journeying to Neighbouring world; If a spacecraft is di.rected to move out in space, away from the earth, it is called a space probe. Several unmanned space probes have either passed by or landed on the planets Mercury, Venus, Mars, Jupiter, Saturn; Uranus and Neptune. They have sent back valuable data and photographs of all these planets. So we have come to know what these planets look like from near, what they are made up of, and what physical conditions prevail near them.