Control system for giant X-ray space telescope

Aircraft Engineering and Aerospace Technology

ISSN: 0002-2667

Article publication date: 1 April 2000



(2000), "Control system for giant X-ray space telescope", Aircraft Engineering and Aerospace Technology, Vol. 72 No. 2.



Emerald Group Publishing Limited

Copyright © 2000, MCB UP Limited

Control system for giant X-ray space telescope

Control system for giant X-ray space telescope

Keywords: Matra Marconi, Space

The mysteries of the black holes and exploding stars will come a step closer to being solved, thanks to the contribution of the UK section of an international space company to Europe's new X-ray telescope, XMM.

Stevenage-based Matra Marconi Space (MMS) UK provided the "attitude and orbit control system" for XMM. After the 10 metre tall space telescope was launched from French Guiana on December 10 the attitude and orbit control system manoeuvred the satellite into its correct position and will continue to hold it steady throughout the ten-year mission. MMS-UK's Project Manager, Mike Backler said: We are delighted to have been able to play such a challenging role in this important scientific mission.

Matra Marconi Space UK has been responsible for the design, development and integration of the attitude and orbit control system on XMM, as well as overall management of the contract for the European Space Agency.

The Attitude Orbit Control System is designed to provide a stable platform for the telescope, which avoids any shaking and can be pointed accurately at any part of the sky for long periods of time. It will enable the 10 metre long satellite to be pointed to within 25 arc seconds (less than one tenth of a degree) of the desired spot in the sky for at least 10 seconds. This is equivalent to aiming a hand-held telescope at a melon placed 180km away and seeing it clearly, without any shaking.

These challenging requirements have been met through careful design of a system, which uses 28 flight units but only weighs 100kg. The attitude and orbit control system uses a number of high precision sensors to keep the spacecraft aligned properly.

Star trackers and Sun sensors allow the spacecraft's computer to recognise the direction in which it is pointing by reference to well-known objects in space. This information is then processed using special flight software and commands are fed to a combination of thrusters and reaction wheels that turn the giant satellite.

Over its ten-year lifetime, XMM will discover up to one million new X-ray sources, ranging from exploding stars to hot interstellar gas and huge disks of material being swept into the jaws of massive black holes. X-rays can only be studied from space because they do not penetrate the Earth's atmosphere.

Matra Marconi Space was selected for this Cornerstone mission of the European Space Agency based on its previous experience in developing attitude and orbit control systems on earlier ESA science missions such as Ulysses, Hipparchos, Cluster and SOHO. In particular, the company has played a leading role in development of the software package which enabled ESA to rescue SOHO after its gyroscopic attitude control system failed. MMS Communications Manager, Alistair Scott, said: We are confident that XMM will be able to complete its ambitious 10 year programme and add to the list of successful missions with which Matra Marconi Space has been associated.

The attitude and orbit control system to be used on XMM is already being installed on another major European scientific satellite, the INTEGRAL gamma-ray observatory, which is scheduled for launch in 2001.

Britain has played a major role in the development of the groundbreaking XMM mission. Two of the telescope's three main scientific instruments have been designed and built under the leadership of Leicester University and Mullard Space Science Laboratory in Surrey. Altogether, through PPARC, the UK's strategic science investment agency, the UK has contributed £75 million to the £500 million project.

Details available from: Matra Marconi Space UK. Tel: +44 (0) 1483 274111, or PPARC. Tel: +44 (0) 1793 442012.