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THE VERTICAL TESTING FACILITY OF THE EUROPEAN XMM SATELLITE

The XMM satellite

The XMM (X-Ray Multi-Mirror Mission) satellite is one of the four key projects of the European Space Agency regarding its long term space research. The satellite includes three grazing incidence telescopes (called Mirror Modules or MM) of the Wolter 1 type, designed to work in the X-ray zone of the 0.1-10 keV with a focal length of 7.5 metres.

Vertical testing facility

AMOS has designed and manufactured the vertical mirror test facility of the European satellite XMM on behalf of CSL. This installation is situated in the new building right next to the old CSL building. The extension includes offices, meeting rooms, work shops, a clean room, a cellar and a pit (11 metres in depth).

The mirrors are inserted into Focal X (the name of the space simulator) with the help of a robot, called manipulator, and placed on the mechanisms which lie on an optical bench. EUV and X-ray beams are then produced with the help of the light sources situated in the pit 11 metres lower down and sent towards the mirrors. They then reflect the beams towards the detectors situated 7.5 metres above a tower that is fixed on the optical bench. The mechanisms that are situated on the optical bench and above the tower enable the various test configurations to be carried out. The optical bench and the tower are supported by three legs fixed on a seismic block (8,135 metres high), lying on elastomer blocks so as to isolate the whole assembly from ground vibrations. In order to do additional test configurations and thanks to its legs, the tower can be inclined to an angle varying from - 2° to + 7.5°. Lastly, the whole installation functions under vacuum inside three chambers : a large chamber 4.5 metres in diameter and 12 metres high which includes an optical bench, the mechanisms, the tower and the detectors; two tubes of 11 metres in height for the X-Ray beams; one chamber 11 metres high for the EUV beam.

All the mechanisms are entirely automated and controlled from a control room. The lower mechanisms enable two translations, one rotation and two tilts of the specimen (XMM mirrors). The upper mechanisms give the possibility of doing three translations and two rotations in order to move the two X-Ray detectors and the EUV detector. The inclination of the tower, the two translations of the manipulator and the opening/closing of the two lateral doors (2,5 metres diameter) are also automated.

The installation of the XMM testing facility is the accomplishment of a completely new high technology which is unique in the world. It has necessitated considerable skill in various areas : mechanical, optical, electronics, electrical, servo control, vacuum and civil engineering. Its conception was made possible thanks to the CAD (Euclid software), to FEM code (SAMCEF) and to optical simulation (Synopsis software). Its manufacturing has necessitated great precision machine-tools (on pieces weighing several tons) and the use of materials and components vacuum-compatible and with strict cleanliness requirements. During assembly and integration, it was necessary to manipulate pieces weighing up to 25 tons and to ensure optimal safety considering the vertical configuration. Lastly, the control of the installation has required the use of special motorisations and high level electronics in order to attain the requested performance.

Some figures

Simulation conditions

Operational temperature : 20 ± 2°C
Vacuum limit : 10-6 mbar
Leak rate : 10-3 mbar l/s
Molecular cleaning : < 2 10-8 g/cm2

Mechanical performance

First eigen frequency of the tower : 14.5 Hz
Number of automated axes : 19
Translation measuring resolution : 1 micron
Rotation measuring resolution : 2,5 arcsec
Repeatability : ± 10 microns

Optical performance (EUV collimator)

Micro-roughness of the mirrors : < 10 Å RMS
Optical quality of the primary mirror : 42 nm RMS Wave Front Error
Optical quality of the secondary mirror : 33 nn RMS Wave Front Error
Image quality : 63 nm RMS Wave Front Error

CUSTOMER : CENTRE SPATIAL DE LIEGE (CSL) - BELGIUM, ESA (European Space Agency) , - THE NETHERLANDS

Creation & Hosting : REALITY MEDIA