Cluster's unique mission formally got under way February 1 when the European Space Agency Commissioning Review Board gave unanimous approval for the start of scientific operations.

An artist's concept the Cluster 2 satellites flying in formation. Photo: Dornier Satellitensysteme GmbH

The final endorsement came after a detailed examination of all aspects of Cluster's ambitious mission to explore the magnetosphere - the region of space dominated by Earth's magnetic field.

For the next two years, four identical spacecraft will be returning simultaneous observations as they follow highly elliptical polar orbits around the Earth. The stream of data sent back by Cluster will enable scientists to obtain their first detailed, three-dimensional view of near-Earth space.

Throughout the afternoon, the Review Board heard a series of presentations covering:

• the performance of the spacecraft since their launches last summer
• the ground segment (including European Space Operations Centre (ESOC) in Germany, the Joint Science Operations Centre in the UK, and the Cluster Science Data System)
• the commissioning of the scientific payload
• and summaries of the first scientific results from each Principal Investigator.

"I am delighted with the first scientific returns from Cluster," said the ESA Science Director, Professor Roger Bonnet, who chaired the Commissioning Review Board. "I am confident that this exciting mission will provide two years of ground-breaking data which will cast new light on our understanding of the interaction between the Sun and Earth."

Another Board member, the Cluster Deputy Project Manager, Alberto Gianolio, took the opportunity to express his appreciation of all the hard work that had taken place in the six months since the quartet first congregated in orbit.

"Today marks the completion of the most complex commissioning programme ever attempted by any space agency," he said. "This successful outcome is a tribute to the dedication and hard work of the thousands of people who have worked on this remarkable mission."

Now that Cluster has cleared this final hurdle with flying colours, some 250 physicists around the world are looking forward to analysing the flood of scientific data from the instruments on board the four spacecraft.

"Due to the large amount of redundancy in the set of Cluster experiments, electrical problems that have affected two of the 44 instruments - ASPOC and CIS - will be largely compensated," said Project Scientist Philippe Escoubet.

"Everyone is eagerly anticipating a scientific bonanza from Cluster in the months and years to come," he added.

The Review Board, which was chaired by Professor Roger Bonnet, included Dr. Chuck Holmes of NASA and representatives from ESA/ESTEC, the Cluster project, the Cluster science teams, the European Space Operations Centre and the Joint Science Operations Centre.