Stellar line-up

As any Red Arrows pilot will tell you, formation flying is far from easy. This is acknowledged with a passing comment on ESA’s website as it celebrates the sixth anniversary of Cluster, the first mission to keep satellites in reasonably tight formation hundreds of thousands of miles above the Earth. Describing the ground-breaking mission with wry humour it reads: ‘Formation flying is a daily reality for the Cluster scientific mission. Some days more so than others.’

With help from a control centre on the ground the four identical satellites have flown in formation, mapping the Earth’s magnetosphere separated by up to as much as 10,000km at certain points in their mission lifetime. The fact that these satellites have remained more or less aligned for such long stretches of time has rightly been hailed by ESA as a marvellous achievement. However, the next generation of the agency’s space missions will require a degree of formation flying accuracy that is far more precise than has ever gone before, Cluster included.