Mars Global Surveyor
Mars Orbiter Camera

Last week, we presented our best image of Viking Lander 2, which had not been seen for nearly 30 years, as well as a candidate for the Mars Polar Lander site. Before these Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) images were taken, we tested out the techniques needed to image landers on the martian surface by observing Viking Lander 1 (VL-1) and Mars Pathfinder (MPF). Here we review our best images of these earlier targets.

Viking Lander 1

The first figure (above) visually tells the story of how VL-1 was found. The initial observations of the location of Viking 1, as originally determined by members of the Viking science team based on sightlines to various crater rims seen in the lander images (left frame), did not show the detailed features we knew from the lander pictures to be in the area. Using geodetic measurements, the late Merton Davies of the RAND Corporation, a MGS MOC Co-Investigator, suggested that we should image areas to the east and north of where VL-1 was thought to be. Timothy J. Parker of the Jet Propulsion Laboratory (Pasadena, California), using sightlines to crater rims seen in the VL-1 images, deduced a location very similar to that suggested by Davies. Our image of that location showed additional, near-field features (rocks associated with a nearby crater) that closely matched the VL-1 images (center and right frame, where B denotes "Volkswagon Rock"). The inset (upper right) is an enlargement, showing the Viking 1 lander.

Mars Pathfinder

As with previous observations of the Mars Pathfinder (MPF) site, we primarily used sightlines to North Peak and the Twin Peaks (second image, left frame). These large, very obvious horizon features make finding MPF fairly easy. The enlargement of loci of the various sightlines (second image, right) shows what we believe are Mars Pathfinder (the larger, lighter-toned spot, arrow) and the 1 m diameter boulder, "Yogi" (dark dot above the MPF).