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This drawing demonstrates the original orbit of Mars Global Surveyor about Mars. The orbit is shown by the white line. One can see that the original orbit of MGS was far from circular! (This drawing is not to scale. It it merely meant to show the elliptical nature of MGS's original orbit)
Click on image for full size
Image from: NASA/JPL

MGS Original Orbit

Originally, the Mars Global Surveyor entered a highly elliptical orbit around Mars (as shown here). MGS's furthest point of orbit or its apoapsis was ~56,000 kilometers. Its periapsis or closest point was only ~150 kilometers above the surface. At this point, it took MGS 45 hours to complete one orbit of Mars.

To get into the near-circular, low-altitude orbit necessary to map the surface of Mars, MGS went through a series of aerobraking steps.

After aerobraking was completed, MGS's orbit looked more like a circle. In 2001, the spacecraft's altitude has ranged from about 310 km - 430 km (near-circular orbit) with an orbital period under 2 hours.

Last modified May 11, 2001 by Jennifer Bergman.

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Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF