XMM science teams prepare to use the X-ray space observatory - SWT 3/4 Dec
7 December 1998Whilst the satellite project team has been organising the arrival ofthe three flight model mirror modules - due to arrive at ESTEC in The Netherlands on 15 December from the CSL testing facility in Belgium - the XMM science teams continue toprepare for the use of the European X-ray space observatory once it isin orbit.
Just over a year from launch, XMM Project Scientist Fred Jansen has just held the 31st meeting of the XMM Science Working Team. Some thirty participants from all over Europe, several principal investigators and many of those involved in the analysis of XMM data were gathered at Estec on 3 and 4 December for an intensive two days exchange of information.
After a status report about the satellite's construction, which is proceeding according to schedule, the meeting dwelt on the multiple and intricate facets of the way the X-ray instruments are going to function. There was considerable discussion about the precise characteristics of the sensitive CCD detectors, notably of its three Photon Imaging Cameras (EPIC), which will detect photons coming from distant, faint, X-ray sources.
The X-ray instruments have to be precisely calibrated much in the same way as the X-ray optics (the three mirror modules). As an example the astronomers must allow for the precise response of the detector instruments, to take care of some of the 'memory effects' present in the X-ray detectors.
The meeting discussed at length the state of progress in developing the very complex software that will be used to process all the data that XMM's instruments will harvest. This is notably one of the shared responsibilities of the XMM Survey Science Centre in Leicester UK, and the Science Operations Centre (SOC) in Villafranca Spain.
It is true that XMM is expected to produce vast quantities of information on these high energy sources in our Universe. An impressive amount of data processing will thus be required before any interpretation can start. The task of managing XMM's huge volume of data is even more daunting when it is recalled that for every known X-ray source that astronomers intend to study, XMM is expected to detect up to a hundred other new sources in its field of view. This so-called 'serenditipous' capacity could provide a catalogue of 100000 sources a year!
Typical exposures during XMM observations will last several hours in order to collect a sufficient number of the elusive photons. The resulting data will consist of numerous parameters, and its analysis is obviously highly complex. The software to be employed will have screen displays which allow entering XMM data files in the clearest and simplest way. The meeting also evoked the 'GUIs': the Graphical User Interfaces which will display XMM discoveries in image form for the most vivid interpretations.
Every science satellite has its nuts and bolts. XMM is ESA9s largest space observatory, the one with the smoothest mirrors ever produced. But the Science Working Team discussion revealed that the mechanics and technology are but one part of this ambitious programme. There is also the immense challenge of receiving, correcting, and exploiting its results. Before any startling pictures (of black holes !) can be released, many millions of lines of software code will have been written, verified and validated from 'A to Z' - or should we say from 'A to X'?