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The HRSC has quite literally provided a ‘new image of Mars, our neighbour’. What makes this camera
special is its ability to ‘scan’ the planet’s surface using nine sensor channels arranged at various angles to the
direction of the orbiter’s flight. From this image data, it is not only possible to obtain large-format images with a
resolution of down to 10 metres but also to generate colour photographs and, most importantly, to derive digital
terrain models of the Martian surface. Before HRSC, global topographical mapping of a planet had never been
accomplished using image data.
On 2 June 2013, 10 years after its launch, the Mars Express spacecraft will have orbited Mars almost 12,000
times. The spacecraft follows an elliptical, quasi-polar orbit and HRSC was switched on during more than 3500 of
those orbits. By the end of ESA’s first planetary mission, currently planned for 2014, the last gaps in the HRSC
map of Mars will have been filled.
•
Ulrich Köhler
Until the puzzle
is complete!
10 years Mars Express
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Complete coverage of Mars, and with stereoscopic imaging – well, almost! There are still a few small gaps in the global
representation of our planetary neighbour. In a Mollweide projection, named after the Leipzig-based mathematician
and astronomer, Carl Brandan Mollweide (1774 - 1825), these last gaps can be seen clearly. All of the usable image strips
acquired using the nadir channel of the High Resolution Stereo Camera (HRSC) on board the Mars Express spacecraft, a
channel with its field of view perpendicular to the surface of Mars, are projected by scientists onto an elliptical surface in
which parallels of latitude are displayed as straight lines and meridians as portions of ellipses. For design purposes, the
monochrome, black and white, image strips are assigned a colour that approximates Martian reality. Due to the presence
of haze and dust in the atmosphere, not all images are of the same quality; many areas have been recorded several times,
from various altitudes and with the Sun at different angles of inclination, which explains the differences in contrast and
brightness.
DLR’s Institute of Planetary Research in Berlin operates the High Resolution Stereo Camera. There, the image data is processed
systematically and made available to more than 50 scientists of the HRSC team from Europe, the United States and Japan, and their
co-workers – and it is also prepared for the data archives of ESA and NASA. The leadership for this science team is also based in
Berlin, at the Freie Universität.
