Abstract. We recomputed the Viking Mars control point network and derived Mars-fixed three-dimensional coordinates of 3739 selected, globally distributed landmarks. Mars Pathfinder and Viking Lander i coordinates as well as data from reanalyzed spacecraft occultation measurements are used as fixed control information in the analysis. The network benefits greatly from recently restored Viking orbiter trajectory data and new planet rotational parameters derived from Pathfinder lander tracking. In our attempt to predict the coordinates of the Viking Lander i site from given Pathfinder coordinates, we find an offset of • 4-5 km of this lander location with respect to the previously reported data. We suggest that this probably is explained by erroneous identification of this landing site in the images. Ninety percent of our landmark coordinates have positional errors of less than 1800 m. This network thus removes previously noted severe offsets between Mars-fixed coordinates and cartographic products.
A new generation of geometrically accurate maps for Mars is in the works thanks to data from the Mars Pathfinder and a mapping project involving reanalyzing images obtained by the Viking Orbiters in the 1970s. During the mapping project it was discovered that the location of the Viking Lander 1 (VL1) on Mars, adopted after its landing in 1976 [Morris, 1980], was not correct. The location represented a basis for previous mapping efforts and is perhaps partially responsible for the poor precision of current maps of the planet.
Availability of maps with good geometric accuracy is of immediate practical importance for pointing orbiting cameras toward specific targets depicted in the maps. Precise maps are also crucial for planning future missions to the surface, such as the Mars Polar Lander, as it is desirable to direct the spacecraft to a specific landing site seen in the maps. Prototypes of new maps of Mars have a geometric accuracy of 1–3 km.
Abstract.Three-dimensional coordinates of 3739 globally distributed control points derived from photogrammetric analysis of Viking Orbiter image data are studied with respect to the shape and large-scale morphology of Mars.
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