The UK in Space

On 4th October 1957 the first artificial satellite began circling the Earth sending out a series of beeps that, for 3 weeks, gave Russian scientists on the ground data about the atmosphere´s upper layers. It was called "Sputnik" meaning `travel companion´ and this nitrogen- filled aluminium sphere with long trailing antennae orbited for 92 days before its orbit decayed and it burnt up in the atmosphere. Satellite technology has progressed remarkably since the days of Sputnik and we now take worldwide communications for granted. Our speaker, Robert Purvinskis, a systems engineer from EADS Astrium, gave us an insight into some of the current missions that his company is involved in.

The company´s core business is the design and manufacture of satellite systems. Usually they are communications satellites in geostationary orbits, which orbit at an altitude of about 35,000 km above the Earth. This type of orbit is used so that the satellite appears stationary with respect to a fixed point on the rotating Earth. It is sometimes referred to as a "Clarke orbit" as the orbit was first popularised by the well-known sci-fi author Arthur C Clarke in 1945 in the magazine "Wireless World".

Slightly nearer the Earth is the orbit known as Medium Earth Orbit or MEO. In this region satellites are usually employed as navigational aids. The American GPS system and the Russian Glonass constellation of satellites operate in these orbits and EADS Astrium is involved in a new European addition known as Galileo. It is planned to have 30 satellites orbiting at an altitude of 23,000km. They will be split into three sets of 10, with each set orbiting in a ring, and each ring inclined so that the whole of the Earth´s surface is covered.

There are many other kinds of orbit that are chosen for a satellite: low earth orbit, polar orbit, Molniya orbit, and near equatorial to name just a few. A satellite will be placed in a particular orbit depending on its mission and what sort of data it needs to collect. For example, it is no good being in an equatorial orbit if you need to take measurements of the thickness of polar ice.

All these different orbits can be applied to satellites of other planets and EADS Astrium is the prime contractor for many missions run by the European Space Agency. Mars Express and Venus Express are two spacecraft that EADS Astrium helped to build and are currently in orbit around Mars and Venus respectively. Other upcoming missions are: the Herschel Space Observatory which will house the largest mirror ever deployed in space (3.5m), the LISA Pathfinder spacecraft to test technology capable of detecting gravitational waves, and the Gaia Telescope which will map more than a thousand million of the stars that make up the Milky Way.