ESA Science News
XMM in safe hands
11 Dec 1999
During the first hours after XMM’s acquisition by the Perth ground station, the spacecraft control teams at
ESOC nursed their baby through its initial in-orbit sequences. Triggered by the onboard timer, the two wings
of the solar array opened faultlessly, the telescope sunshield equally well. The star trackers were switched on
and the spacecraft’s reaction wheels were spun up.
On a large screen in the Main Control Room, an animation showed XMM’s position in space, moving away from
Earth on its first orbit. Dietmar Heger, spacecraft controller commented: “It’s going very, very nicely. Almost
better than the simulations we have been through before launch”.
To reach its definitive orbit, commands will be sent to the satellite to fire its onboard motors several times.
On the first orbit, in two burns some 22 and 24 hours after liftoff, the velocity of the spacecraft will be
increased so as to start raising the perigee. A second perigee raising manoeuvre will take place at +69 hours
and a third at +117 hours. At the start of orbit 4 another manoeuvre will fine-tune the apogee, before XMM is
configured for its definitive operational orbit (114,000 x 7,000km)
During the early orbit phase, part of XMM science payload (notably the three EPIC cameras) are to be
switched on, in order to vent the instruments of any residual air. On orbit 5, the radiation monitor will be
switched on (to start collecting data on the passages through the Earth’s radiation belts) and on the sixth orbit,
the door to the Optical Monitor will be opened.
XMM will be placed in a “sleep mode”, pointing at a bright star that will not be occulted during this period
over the Xmas and New Year holidays. Operations will resume on 4 January. A long phase of commissioning the
spacecraft in orbit and calibration of the instruments will precede the start of the first science observations,
scheduled next spring.
USEFUL LINKS FOR THIS STORY
* More news and video clip
* ESOC homepage
IMAGE CAPTIONS:
[Image 1:
http://sci.esa.int/missions/image.cfm?TypeID=20&ContentID=8411&table=ContentTable]
Dietmar Heger (XMM spacecraft controller) and his “baby in space”. “It’s going better than the simulations”.
ESOC main control room, 10 December 1999.
[Image 2:
http://sci.esa.int/missions/image.cfm?TypeID=20&ContentID=8411&ImageID=3870&table=ImageTable]
Alan Smith, flight operations manager (on right) explaining XMM first sequences to Jocelyne Landeau (ESOC
PR) and Martin Huber. Mission control room at ESOC, 10 December 1999.
