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Emily Lakdawalla • Jan 03, 2011

It's Phobos season again for Mars Express

The Mars Express blog has been reactivated today, as a new series of Phobos flybys is already underway. Mars Express gets a series of 10 to 12 reasonably close flybys of Phobos once every five months, and is the only orbiter currently at Mars that can see the "far side" of Phobos. Mars Odyssey and Mars Reconnaissance Orbiter can only see Phobos' Mars-facing hemisphere, because those two orbit much closer to Mars than Phobos does.

Schematic diagram of Mars Express' Phobos encounters
Schematic diagram of Mars Express' Phobos encounters Phobos orbits Mars in a nearly circular, equatorial orbit. Mars Express orbits Mars in an elliptical, polar orbit with a close approach in the high northern latitudes. Mars Express' orbit drifts westward over time. Most of the time, Mars Express is far from Phobos, but about once every five months there is a series of 10 to 12 close encounters with the moon, during which Mars Express shifts from studying Mars to studying Phobos.Image: ESA
Phobos over Mars from Mars Express
Phobos over Mars from Mars Express The High Resolution Stereo Camera (HRSC) on ESA's Mars Express' spacecraft caught Phobos over Mars' limb on March 26, 2010. The waviness of Mars in the background is a by-product of the line-scanning nature of HRSC.Image: ESA / DLR / FU Berlin (G. Neukum)

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