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N.M. Hoekzema, W.J. Markiewicz, H.U. Keller (MPAE, Katlenburg-Lindau, Germany), K. Gwinner, G. Neukum (DLR Berlin, Germany)
A primary task for the Mars Express (MEX) orbiter is to map Mars in stereo with the High Resolution Stereo Camera (HRSC). The Martian atmosphere contains large amounts of dust and other aerosols that scatter light and influence the images. Therefore, image analysis requires careful consideration of atmospheric effects. An essential parameter in this context is the optical depth. During periods that the spacecraft circles within a few tens of degrees from the terminator it will usually be possible to map optical depth from normal HRSC stereo images by analyzing contrast differences. The expected precision is better than about 0.1. We present the theory behind such retrievals and discuss its applications and limitations. The method is validated with airborne HRSCa images of the French Alps. We discuss two alternative ways to analyze images. The first is using large images; the second is dividing larger regions into smaller sub-regions and analyze those separately.
Standard optical depth retrievals, via methods common in Earth remote sensing, are currently hampered by the absence of regions on Mars for which the surface albedo is well known. We suggest a way to improve this situation. It should be possible to map the surface albedo from stereo images that are obtained while MEX is rotated from its normal nadir pointing position towards the direction of flight by e.g., 60°. We offer the basic theory behind such albedo mapping, and discuss some of its applications and limitations. We hope for an accuracy in the retrieved albedos of up to 1--2
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The author(s) of this abstract have provided an email address for comments about the abstract: hoekzema@linmpi.mpg.de
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.