Satellites

The word ‘satellite’ describes an object that revolves round a heavenly body. The Earth’s best-known satellite is none other than the Moon! (It’s called a natural satellite.) The artificial satellites that have been launched since 1957 differ from each other in shape, size, mass or the use to which they are put. But they all have one thing in common: their very high speed.

This depends on the satellite’s altitude and trajectory but is always very fast: around 7.8 km/second (28,000 km/h) for the satellites closest to the Earth (at an altitude of about 200 km) and 3 km/second (10,800 km/h) for geostationary satellites, those furthest away at an altitude of 36,000 km.

Scientists use satellites placed in orbit round the Earth to observe the planet, its climates and oceans, as well as the surrounding Universe.
Most of their numerous uses can be listed in four main categories :

1. For satellites in high orbits
   > telecommunications (e.g. Astra)
   > Earth observation (remote sensing, military surveillance and reconnaissance, weather forecasting, the environment, location and navigation, etc.)
   
2. For extra-atmospheric satellites
   > astronomy (e.g. Hubble, XMM)
   
3. For satellites capable of long journeys in the Space vacuum
   > planetary probes (e.g. Voyager, Cassini-Huygens)
   
4. For satellites in free-fall orbits resulting in weightless conditions
   > Space stations (e.g. MIR, ISS)

Satellite photos taken by SPOT 4

The SPOT satellites, developed by France, make exceptional observers: they can distinguish details down to 10 metres! Imagine binoculars which would let an observer perched on a high tower at St Laurent du Maroni spot a vessel in Kourou’s Pariacabo harbour! The SPOT satellites are a wonderfully productive source of images and their pictures of our planet have revolutionised several fields of activity. Once interpreted, they can be used for national or regional planning and development or to monitor the evolution and consequences of a natural phenomenon.

SPOT'Art

Images from the SPOT satellites can be stunningly beautiful. Certain astonishing coloured patterns could be mistaken for works of art and have been displayed in exhibitions or published in books. This branch of art has been called SPOT'Art.
Some of these images are displayed at the Space Museum at the Guiana Space Centre.