ESA Science & Technology - Clear skies for Cluster II launch campaign

They were delighted to hear that all four spacecraft have been delivered successfully to Baikonur and that the launch campaign is now under way.

The giant Antonov 124 cargo plane, the largest aircraft in the world, took off from Basle-Mulhouse airport on 27 April with the first pair of Cluster II spacecraft (FM 6 and 7) on board. Alongside their protective containers were ten 'sea' containers packed with ground support equipment and other essential hardware.

After a stop and customs check in Moscow, the spacecraft were safely delivered to Baikonur Cosmodrome in Kazakhstan the following day. The aircraft touched down at 10.45 a.m. local time on the same runway that was used by the Russian Buran space shuttle in 1988.

Another 75 tonnes of equipment, including the FM 5 and FM 8 spacecraft plus ten more containers, were flown out of Basle by a second Antonov on 3 May, with arrival at Baikonur on the evening of the fourth. This later time of arrival meant that the spacecraft containers had to remain on the Antonov overnight. However, on the morning of 5 May they, too, were lifted onto a special train for despatch to the Cluster II spacecraft processing facility.

Little time was wasted in getting the launch campaign under way. By 10 May, FM6 had successfully completed the first system tests with remote control of the scientific experiments from ESOC, and was being prepared for boom deployment and reaction control system tests.

At the same time, electrical tests on FM7 were well under way, and were soon to start on FM 8. The fourth spacecraft, FM 5, was being set up in the Upper Composite Integration Facility while awaiting a decision on thruster re-integration.

Further good news came on 11 May, when a Material Review Board accepted the recommendations of the Cluster II project team to replace a suspect batch of thruster seals and leave the remaining ones on the spacecraft.

The batch of seals that was suspected to be flawed will simply be replaced by another batch which have passed exhaustive trials by Daimler-Chrysler Aerospace in Germany. The test results on the new batch confirmed that the seals would survive the full Cluster II mission lifetime of two years. This included firing the thrusters for 12,500 pulses and simulating a worst case scenario in which they will be utilised as a back-up if a problem arises in the main spacecraft propulsion system.

The remaining thruster seals have also been validated using the same procedure, with equally positive results. As a result, the project team has full confidence that all of the seals will be able to perform without risk throughout the entire mission.

A Cluster II spacecraft carries eight thrusters, each of which contains four seals made of a soft polymer called kalrez. The thrusters are required to manoeuvre the four satellites and change their separation distances so that they can achieve the maximum science return from their two year exploration of the magnetosphere.

Under current plans, the Cluster II launches are still set for 12 July and 9 August.