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The ESA probe Mars Express has been orbiting Mars in an elliptical polar orbit since 25 December 2003 – at an angle of almost 87° to the equatorial plane – which brings the orbiter to an altitude of just 240 kilometres above the planet's surface three times a day (red orbit). The furthest distance of the orbiter from Mars during the orbit is around 10,000 kilometres.
Phobos, a potato-shaped body with dimensions of 26.8 kilometres × 22.4 kilometres × 18.4 kilometres, orbits the planet in an almost circular equatorial orbit at a distance of 6,000 kilometres. Deimos, which, with its dimensions of 15.0 kilometres × 12.2 kilometres × 10.4 kilometres is the smaller of the two moons, orbits Mars at a distance of around 20,000 kilometres.
During the almost six-year long Mars Express mission, the geometrical configuration of the two moons relative to the probe on 5 November 2009 presented a unique opportunity to capture the moons in a sequence of images. Phobos and Deimos were directly in the field of view of the orbiter's HRSC (High Resolution Stereo Camera).
Credit: FU Berlin.
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