Thursday, September 20, 2007

Mars Express

Credit: ESA/DLR/FU Berlin (G. Neukum)

The 2003 launch window was very ambitious and largely successful. The first spacecraft to launch was Mars Express and the Beagle 2 Lander. These two spacecraft were the first efforts by western Europe to reach Mars: Mars Express was the first planetary mission attempted by the European Space Agency, and Beagle 2 was developed by a consortium of British universities and businesses, the lead party being the University of Leicester.

The Mars Express Orbiter had a number of mission goals, including:
  • to image the entire surface at high resolution (10 meters/pixel) and selected areas at super resolution (2 meters/pixel);
  • to produce a map of the mineral composition of the surface at a 100 meter resolution;
  • to map the composition of the atmosphere and determine its global circulation;
  • to determine the structure of the sub-surface to a depth of a few kilometres;
  • to determine the effect of the atmosphere on the surface; and
  • to determine the interaction of the atmosphere with the solar wind.

    The Beagle 2 Lander, on the other hand, was to:
  • determine the geology and the mineral and chemical composition of the landing site;
  • search for life signatures (exobiology); and
  • study the weather and climate.

    The spacecraft were launched on June 2, 2003 from the Baikonur Cosmodrome in Kazakhstan, using a Soyuz-Fregat rocket. Mars Express and the Fregat booster were initially put into a 200 km Earth parking orbit. The Fregat was fired again, 89 minutes after launch, to put the spacecraft into a Mars transfer orbit. Two days later, a trajectory correction maneuver was performed to aim Mars Express towards Mars and allow the Fregat booster to coast into interplanetary space.

    After a mere six-month voyage (Mars and Earth were, at that time, closer to each other than they had been in the previous 60,000 years), the Beagle 2 lander was released on December 19, and the orbiter entered Mars orbit on December 25, 2003. Mars Express' orbit was later adjusted by four more main engine firings to the desired 259 km × 11,560 km near-polar (86 degree inclination) orbit with a period of 7.5 hours. During periapsis the top deck of the spacecraft is pointed down towards the Martian surface, and during apoapsis the high gain antenna is pointed toward the Earth for uplink and downlink communications. After 100 days the apoapsis was lowered to 10,107 km and the periapsis raised to 298 km to give an orbital period of 6.7 hours.

    The above photo was taken by the High Resolution Stereo Camera (HRSC) on board Mars Express, showing Crater Galle (aka the "Happy Face" Crater), an impact crater located on the eastern rim of the Argyre Planitia impact basin on Mars. Crater Galle is named after the German astronomer J.G. Galle (1812-1910), and was first pointed out in images taken during the Viking Orbiter 1 mission. The picture is a mosaic of overlapping images gathered during five separate orbits. The ground resolution ranges between 10-20 meters per pixel, depending on the location within the image strip. Crater Galle is located near 51° South, 329° East. North is up.

    The image shows Crater Galle containing a large stack of layered sediments forming an outcrop in the southern part of the crater. Several parallel gullies, possible evidence for liquid water on the Martian surface, originate at the inner crater walls of the southern rim. The crater's interior also shows a surface that is shaped by "aeolian" (wind-caused) activity as seen in numerous dunes and dark dust devil tracks that removed the bright dusty surface coating.
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