About 1000 Viking Orbiter red- and violet-filter images have been processed to provide global color coverage of Mars at a scale of 1 km/pixel. Individual image frames acquired during a single spacecraft revolution were first processed through radiometric calibration, cosmetic cleanup, geometric control, reprojection, and mosaicking. We have produced a total of 57 "single-rev" mosaics. Phase angles range from 13x to 85x. All of the mosaics are geometrically tied to the Mars Digital Image Mosaic, a black-and-white base map with a scale of 231 m/pixel. We selected a subset of single-rev mosaics that provide the best global coverage (least atmospheric obscuration and seasonal frost); photometric normalization was applied to remove atmospheric effects and normalize the variations in illumination and viewing angles. Finally, these normalized mosaics were combined into global mosaics. Global coverage is about 98% complete in the red-filter mosaic and 95% complete in the violet-filter mosaic. Gaps were filled by interpolation. A green-filter image was synthesized from an average of the red- and violet-filter data to complete a 3-color set. The Viking Orbiters acquired actual green-filter images for only about half of the Martian surface. The final mosaics have been reprojected into several map projections: Sinusoidal Equal-Area (global), Lambertian Equal Area (east- and west-hemisphere views), Polar Stereographic (1/2 planet views of the northern and southern hemispheres), Mercator (equatorial region), and Orthographic views centered on 6 different positions on the Martian surface. The Orthographic views are most like those seen by a distant observer looking through a telescope. All versions exist both with and without latitude-longitude overlays.
