Mars Express, the European Space Agency's (ESA) first planetary mission, is a true marathon runner among spacecraft. Launched on 2 June 2003, the spacecraft arrived at Mars during the night of 25 December that same year. On 26 October 2019, this spacecraft completed its twenty-thousandth orbit around Mars. Mars Express is in good company in Martian orbit: NASA’s Mars 2001 Odyssey and Mars Reconnaissance Orbiter have also been studying the Red Planet for more than 10 years. Odyssey has been in orbit since 2001 and Reconnaissance Orbiter since March 2006.
The High Resolution Stereo Camera (HRSC) developed and built by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) in collaboration with German industry, has been photographing the planet's surface on board Mars Express since January 2004 – at resolutions of up to 10 metres per pixel, in colour and in three dimensions. This is the first global topographic collection of image data for a planet other than Earth. In total, the resistant stereo scanner has recorded 363 gigabytes of raw data that have been pre-processed on Earth to produce 5.5 gigabytes of scientifically useful image data. The HRSC has recorded 75 percent of the planet’s approximately 150-million-square-kilometre surface at image resolutions of 10 to 20 metres per pixel.
The topographic image maps generated using the HRSC are of great scientific benefit. Digital HRSC terrain models are also used when selecting landing sites, such as for NASA's InSight geophysical observatory or the ExoMars (ESA, due to launch in 2020), Curiosity and Mars 2020 (NASA) rovers.
The orbit of Mars Express is highly elliptical, passing from pole to pole and taking the spacecraft to distances between 240 kilometres to over 10,000 kilometres from the Martian surface. The 'anniversary' of the twenty-thousandth orbit gave researchers in the HRSC experiment team, led by Ralf Jaumann at the DLR Institute of Planetary Research in Berlin, the opportunity to visit Mars during a simulated overflight of various 'chaotic areas', outflow channels and craters to the east of the Valles Marineris canyon, just north of the equator.