Phobos fly-by orbital characteristics animation. NASA’s Mars Odyssey (MO) and Mars Reconnaissance Orbiter (MRO) are in a low orbit around Mars.

In observing Phobos, Mars Express benefits from its highly elliptical orbit which takes it from a closest distance of 270 km from the planet to a maximum of 10 000 km, crossing the 9000 km orbit of the moon. Mars Express imaged the far-side of Phobos (with respect to Mars) for the first time by flying outside the spacecraft’s orbit around Mars.