This photoindex shows locations of the Mariner 9 pictures that are the primary source materials for the albedo marking, overlays in the U.S. Geological Survey's "Atlas of Mars." All pictures were taken by the "A" camera. The individual pictures were selected to provide complete coverage of the planet at the smallest scales possible with a minimum of overlap. They thus provide the most compact data set attainable. Most of the pictures used were from sequences designed by the Mariner 9 imaging team for computing a planetwide control net. Because they did not provide complete coverage, they were supplemented with global-scale pictures taken late in the Mariner 9 mission, and, where the latter were not available, with pictures taken primarily for topographic and geologic mapping. For a listing of topographic and geologic mapping pictures, see "Index of Mariner 9 Mapping Pictures of Mars" (1975). The pictures on this plot have been specially processed in the computer to remove density variations across the frame caused by sun elevation.

The hatched area in the north polar region was covered with frost or snow when pictures, were taken. Albedo information is therefore not available from Mariner 9 in that area.

The frame outlines were drawn according to spacecraft tracking information and have been verified by matching picture images with known locations of surface features. Parts of some pictures are degraded by foreshortening and poor illumination, so outlines show useful image area only, not necessarily frame edges.

Each frame is identified by a number assigned by a clock on the Mariner 9 spacecraft. This number, or "DAS" time (for Data Automation Subsystem), indicates the number of 1.2 second intervals between the time the spaecraft was launched and the time the picture was taken. Owing to the varying times at which this number was recorded by ground receiving stations, the same picture may be identified in various tabulations by numbers differing by up to eight units in the last digit.

The designation "M 25M 3PIA" is an abbreviation for "Mars 1:25,000,000, third edition base, phowindex of albedo mapping pictures."