Science Operations Centre coping well with the steady stream of XMM-Newton data
19 October 2000
An ancient castle looks over ESA's VILSPA establishment, huddled inthe hills on the outskirts of Madrid. Its medieval stonework is thefirst to receive the early morning sunlight, then the line ofEuropean flags and the large white antennae which point skywards. On10 December last, one of these big dishes followed XMM-Newton as itclimbed into orbit.Today, the X-ray observatory's Science Operations Centre (SOC) at VILSPA is in full swing. After the commissioning of the spacecraft and the calibration and performance verification of its 6 science instruments, the mission has now entered its operational, routine phase.
Since 1st July, the X-ray space observatory has been sending down a continuous steam of science data. During each 48 hour orbit, there are 3 or 4 observations of celestial targets, chosen by the telescope's principal investigators, and those selected after the first call for proposals. Certain observations can last more than 10 hours - although the scientists prefer to count in kiloseconds!
Some 30 people make up the Science Operations Centre. Laura Tomas is a member of the team producing the "time-line", programming the observations during each orbit. A computer programme first produces a list of possible observation sequences, then in a manual effort, a final choice is made and the timeline is sent to the spacecraft controllers at ESOC in Darmstadt.
Fitting a maximum into the timeline is no easy task given the constraints. Six months ago, 48 hours were required to plan one orbit's observations. Today this has been cut down to less than a day, and timelines are being produced five to six orbits ahead!
A target must first of course be visible, then the observatory has to be slewed to point towards it, and there is the set-up time before an instrument can start counting the elusive X-ray photons. Timelines, untill the end of the year when a new antenna will become operational, have to allow for the one hour "apogee gap" when the spacecraft is out of visibility of the two main tracking stations in Perth and Kourou, and for the handover between the stations. There are also the eclipse periods (as at present) and exceptional events such as meteor showers like the forthcoming Leonids in November when XMM-Newton has to protect its golden mirrors and turn its back on the particle onslaught.
There are, above all, the radiation constraints. When the satellite passes close to the Earth, at perigee, it has to "batten down the hatches", closing all the instrument shutters to protect them from radiation that could harm their sensitive detectors.
Despite many constraints, XMM-Newton science operations have reached a very high level of efficiency. Norbert Schartel is group leader of the Mission Planning and Community Support Team which interfaces with the increasing number of scientists the telescope is now serving and the calibration scientists who are still "tweaking" the instruments to get even better quality data.
"After much fine tuning we are now using more than 95% of the available observing time" says Norbert. "Filling the timeline to such an extent, regularly giving XMM-Newton its two-day dose of work, is a major achievement".
This efficiency is no mean feat considering that the Science Operations Centre was not yet fully operational when XMM-Newton was launched. "The operational efficiency has increased substantially" explains Damien Texier, Instrument Support Team leader. "Since the beginning of the operational routine phase, we have obtained 85 to 95% of the scheduled observation data, depending on the instruments."
The final component of the SOC systems is soon to be introduced. The first public version of the Science Analysis Software (SAS) is due to be made available in a few weeks. This will enable scientists to easily extract and interpret the observation data, which is sent to them in large electronic files, either by the Internet or on CDs.
Many of the members of the Science Operations Centre have participated in the analysis of data. "A special issue of Astronomy and Astrophysics, devoted to the XMM-Newton mission is planned for early next year" says Jean Clavel, XMM-Newton Science Operations Manager. "At the last count, there will be 52 papers and all eight scientists on my SOC team are co-authors of at least one or two papers. Like the science community, everyone here is eager to use XMM-Newton for their own work. That's why we have a really motivated team."
In the Control Room, Nora Loiseau is one of the six operators constantly watching over XMM-Newton's science instruments. It is here that the incoming raw science data first appears on the consoles. "Admittedly our shift work, particularly at night can lead to a somewhat solitary existence. But we are all very privileged people. We are the first to see these distant stars and galaxies that the telescope is observing". Her personal picture album is further example of the great dedication of the XMM-Newton Science Operations team.
Special thanks to Bruno Altieri and everyone in the XMM-Newton SOC team.
