The Cluster 2 satellite array
consists of four separate units - Salsa
orbiting the Earth in a tetrahedron
enabling them to make first detailed three-dimensional
study of the changes and processes taking place in near-Earth space.
The Cluster 2 mission is to spend the next two years studying the changes and variations in the solar winds incoming energetic particles, finding out what they do to the magnetosphere (in collaboration with SOHO and Ulysses) and finding the effects on the Earths' weather patterns. The mission is taking place now so as to take advantage of a period of peak activity in the Sun's 11-year cycle, when sunspots and solar radiation reach a maximum.
Each giant disc shaped piece of the array weighs 1200 kg, and measures 1.3 metres high and 2.9 metres across. In the centre is a cylinder with an aluminium honeycomb structure covered with a skin of carbon fibre reinforced plastic. The equipment panel inside this cylinder supports the main engine, two high-pressure fuel tanks and other parts of the propulsion system. Hanging from the sides of theis cylinder are six fuel pods. Secreted else where on the satellite are five nickel-cadmium batteries intended to provide power when the array passes into the Earths shadow.
Cluster 2 will be the first space science mission ever to fly four identical spacecraft simultaneously (after the initial Cluster mission was destroyed during the Ariane 5 disaster). Once the quartet have been inserted into highly elliptical polar orbits, ranging from 19 000 to 119 000 km above the Earth, they will spend the duration of the mission travelling from the magnetosphere into interplanetary space and back again, each satellite transmitting one gigabyte of data per day as it is collected by its eleven instruments
Information taken from