The locations of Mars, its moons and Mars Express when the images were taken.
ESA’s Mars Express has been circling Mars in an elliptical polar orbit since 25 December 2003 at an angle of roughly 87° to the equatorial plane. This orbit brings the spacecraft just 240 kilometres from the planet’s surface thrice a day. The furthest distance of the orbiter from Mars is about 10,000 kilometres.
Phobos is a potato-shaped moon, 26.8 × 22.4 × 18.4 km in size. It circles the planet in an almost circular equatorial orbit at a distance of 6000 km. Deimos, which has dimensions of 15.0 × 12.2 × 10.4 km, is the smaller of the two moons. It orbits Mars at a distance of roughly 20 000 km.
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).