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The XMM Mission

John Credland
Head of Scientific Projects
ESA Directorate for Scientific Programmes

 
The launch of the X-ray Multi-Mirror (XMM) telescope on flight V119, the first commercial launch of Ariane-5, will mark another important milestone for European Space and the Agency's Scientific Programme.
The mission, conceived in the late 1970s, entered the assessment-study phase in 1982 and was adopted as a 'Cornerstone Mission' in the then new Horizon 2000 Programme approved by the Science Programme Committee in 1984. The industrial studies were completed in 1988 and the scientific payload selected in 1989.

A major challenge for the mission designers from the outset was the development of the mirror technology enabling the replication of the telescope mirrors to a sufficient accuracy to meet the stringent mission requirements. Development work in industry started in 1984 using carbon fibre reinforced plastic technology, augmented in 1986 with development work on electroformed nickel mirror shells. The latter technology was chosen as the most reliable prior to the start of the spacecraft development programme in 1994. As the mirror technology was being developed, the payload configuration evolved from 19 telescopes in 1983 through several stages to the current three-telescope configuration in 1991.

The industrial phase commenced in 1994, resulting in the current configuration of a 10 m high spacecraft, over 4 m in diameter, and with a launch mass of just under 4 tonnes. This is the largest scientific spacecraft yet developed in Europe.

The spacecraft procurement programme has been extremely successful and all essential elements of the mission are now in place and configured for launch: the spacecraft including its scientific payload; the mission operations centre at ESOC in Germany; the science operations centre at Vilspa in Spain; and finally the Ariane V504 launch vehicle.

As an additional 'first', XMM is the first ESA mission whose launch has been insured under the new ESA corporate policy endorsed by the Administrative and Finance Committee (AFC) at the end of September. The partial insurance of the mission, which will enable the European science community to continue to participate in x-ray astronomy in the case of loss of mission during the launch phase up to injection, is a part of the Agency's corporate risk-assessment policy established as a foundation for the future.

Europe and its scientific community will take a quantum leap forward in X-ray astronomy with the launch of XMM.