Somewhere in secret files in the United States and the CIS, are pictures that, if magnified, would show your house, your family’s car, and perhaps even you, walking down the street. All these would be taken by spy satellites, hovering high above Earth’s atmosphere, fitted with super – powerful cameras.
Apart from the dramatic pictures that these ‘eyes in the sky’ can give, they also provide other, vital data. Other spacecrafts circling the Earth monitor the weather or survey the surface for mineral wealth. Everything on our planet has its own special way of reflecting, transmitting and absorbing light. So from space a field of wheat, for instance, looks different from a field of maize, and an outcrop of iron ore looks different from one of coal.
Satellites gather data with a variety of instruments – photographic cameras, TV cameras, infra-red detectors. TV and radio signals are beamed down to receiving stations on the ground. Capsules containing exposed film can return to Earth by parachute or the film can be scanned electronically, and the resulting signal transmitted to earth.
Using computers, detailed colour pictures can then be built up from the spacecraft information, allowing scientists to spot crop diseases and forest fires, search for valuable minerals, follow the movement of oil slicks, that threaten to pollute beaches, and even watch the migration of animal herds. Satellites also provide early warning of approaching blizzards, or of hurricanes as they develop out at seas and then move inward to land.
The world’s major space agencies have agreed to increase their co-operation in observing Earth from space. Information from orbit will show clearly what effect the human race is having on its environment. It will allow each nation to make better use of its resources and to be warned of any impending natural or man-made disasters. Increasingly, our eyes of the sky will give us a fresh view of the Earth and the knowledge we need to take better care of our home planet.
Long ago, sailors used to set their ship’s course according to the position of the Sun and stars. Today, navigation satellites act as artificial ‘stars’ by which pilots on the sea or in the air can find precisely where they are at any instance. Ships and aeroplanes need only pick up the signals from three separate satellites to be able to work out their own position. The same principle applies to our car navigation systems or GPS’s.
