The world was shocked as the Soviet Union launched a small satellite called Sputnik, on 4th October 1957, and the Space Age began. Sputnik itself was little bigger than a basketball but, since that time, over 4500 satellites of varying sizes have been launched into Earth orbit. Some fifty countries now either own a satellite or have a share in one. Several hundred orbiting satellites make possible commonplace things like
- Google Earth,
- weather forecasting,
- military espionage,
- GPS navigation,
- global TV and Internet connections.
Some satellites are geostationary. Others circle the Earth every 90 minutes or so. In both cases particular orbits are favourable. As the activity on the right shows, there is crowding of spacecraft at certain heights above the Earth’s surface.
The social implications of some of these satellites are enormous. But there is also a growing danger from the debris associated with them.
Watch 'Eyes in the Skies’, a fascinating half-hour film about imaging satellites, and their implications for privacy, earth observation and geosciences.
What is space debris and where does it come from?