Between 23 July and 15 September 2008 Mars Express performed a series of eight fly-bys of the martian moon Phobos, at distances ranging between 4500 and 93 km from the centre of the moon, conducting some of the most detailed investigations of the Moon to date. In observing Phobos, Mars Express benefits from its highly elliptical orbit which takes it from a closest Mars approach of 270 km above the surface up to a maximum of 10 000 km distant from the planet's centre, crossing the 9 400 km orbit of the moon. Like our Moon, Phobos always shows the same side to the planet, so it is only by flying outside the orbit that it becomes possible to observe the far side. The other spacecraft presently orbiting Mars do so at much lower altitudes, and therefore only see the planet-facing side of the moon.
On 23 July 2008, the High Resolution Stereo Camera on board the ESA’s Mars Express took the highest-resolution full-disc image yet of the surface of the moon Phobos.
The image data was acquired from a distance of 97 km with a spatial resolution of about 3.7 m/pixel in orbit 5851. These images have surpassed all previous images from other missions in continuous coverage of the illuminated surface at the highest spatial resolution of 3.7 m/pixel.
This image has been geometrically corrected and exhibits the original illumination and photometric conditions.
