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Mars Global Surveyor Mars Orbiter Camera Release: MOC2-10
Caption
This movie was created by combining the eight MGS/MOC MOI-22 day
approach images into a map of Mars, and then digitally reprojecting
that map onto a sphere. This is the same process used by the Hubble
Space Telescope team in making its rotation movie
from HST data. The HST data were acquired when Mars was viewed
more or less "face on," whereas MGS/MOC viewed the planet at
half-phase. Thus, each of the eight MOC images required processing to
remove the overall shading (the photometric function).
Software provided by the Hubble Space Telescope Mars Monitoring team
was used for this purpose. This software was also used to create a
map projection of each image. These were then mosaiced together to
create a map of the visible part of the planet (areas south of
66.4°S were not ever seen). Owing to foreshortening in the polar
regions, some cosmetic processing was needed in areas south of about
35°S as well. Once the final map was created, a limited amount
of enhancement was applied to sharpen features, and the resulting
image was "mapped" onto a sphere using computer graphic software. A
camera within this software was place at a relative distance and
appropriate magnification to recreate the view seen from MGS, and an
illumination source was set at the right location to simulate the sun.
A set of test images were then created to compare with the original
images. When the simulation recreated the input images, the rotation
of the planet was simulated, and the camera position moved to observe
the planet "face-on."