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Global views and Phobos

Mars Express has a polar orbit and the spacecraft travels on elongated ellipses. During each seven-hour orbit, the spacecraft approaches the surface to about 300 km and then moves away to a distance of about 10.000 km. Images from this high altitude are typically obtained to observe weather patterns, for creating global views of the surface and for calibration purpose. The sensors of the HRSC are directed over a wide extended area in a sweeping movement. That is why this type of observation is also called 'broom calibration'. The field of view of the line sensors that are arranged perpendicular to the flight path are pushed across the surface like a broad 'brush stroke'. In this way, all the sensors scan the surface at the same angle of observation one after the other, resulting in a time interval. This becomes visible in the color overview image (Mars with grid), where Phobos can be spotted at different locations because it moved on during the scan process. In the post-processing for such images as presented here, the individual color images are then overlain to create the full color view. Phobos was individually reconstructed to give a consistent impression of the scene.