The USSR's Sputnik 1 was the first artificial satellite to enter Earth's orbit.This 83.6 kg metal sphere transmitted signals back to Earth for three weeks before its batteries failed.
In 1958 the USA began to launch its satellites.Five went into orbit.All of the earliest satellites have since crashed back to Earth,except Vanguard 1 (USA ,1958) which is still in space and likely to remain so for another 200 years.
Over the past 50 years,many more artificial satellites have been launched, with a greater range of uses.
Astronomy - The Hubble Space Telescope has been taking photographs of distant galaxies since 1990.
Communications - Over 5000 satellites have been launched to transmit telephone,radio and television signals around the world . Fewer than half are still orbiting and many have stopped working.
Earth observatory satellites - These transmit images of the weather and the Earth's environment.They helped to show the depletion of ozone layer.
Global positioning system - This is the system of 24 linked satellites that allows people to pinpoint their exact position anywhere on earth. The system is operated by the US Department of Defense and is used by aircraft and ships GPS systems are now common in cars too.
Military satellites - Governments use these 'spies in the sky' for surveillance but their precise functions are secrets.
Sources : Whitaker's world of facts
In 1958 the USA began to launch its satellites.Five went into orbit.All of the earliest satellites have since crashed back to Earth,except Vanguard 1 (USA ,1958) which is still in space and likely to remain so for another 200 years.
Over the past 50 years,many more artificial satellites have been launched, with a greater range of uses.
Astronomy - The Hubble Space Telescope has been taking photographs of distant galaxies since 1990.
Communications - Over 5000 satellites have been launched to transmit telephone,radio and television signals around the world . Fewer than half are still orbiting and many have stopped working.
Earth observatory satellites - These transmit images of the weather and the Earth's environment.They helped to show the depletion of ozone layer.
Global positioning system - This is the system of 24 linked satellites that allows people to pinpoint their exact position anywhere on earth. The system is operated by the US Department of Defense and is used by aircraft and ships GPS systems are now common in cars too.
Military satellites - Governments use these 'spies in the sky' for surveillance but their precise functions are secrets.
Sources : Whitaker's world of facts
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