NASA Lewis Research Center's
Contribution To The Mars Pathfinder Mission

NASA Lewis Research Center has been involved in the Mars Pathfinder Mission nearly from the beginning. The Mars Solar Energy Model (G. Landis and J. Applebaum) provided an early demonstration that sufficient solar energy is available at Mars to provide operating power for a spacecraft and lander. This solar energy model was incorporated into the computer model used by JPL to design solar arrays for the Pathfinder lander, and the Sojourner Rover. since then, Lewis scientists have designed, built, and delivered hardware for three sensors incorporated onto the rover. Also delivered were several small tungsten points for removing electrostatic charge accumulated during rover surface operations.

The Material Adherence Experiment (MAE), will quantify how much dust settles out of the martian atmosphere. The Viking landers showed that the atmosphere of Mars contains a large amount of suspended dust. The MAE consists of two sensors. The first sensor is a solar cell (G. Landis and P. Jenkins) which will measure how much light is obscured from the cell by dust that settles on it. Results will show how opaque Mars dust is, and how rapidly it settles out of the martian atmosphere. The second sensor is a quartz crystal monitor (G. Hunter and L. Oberle) which will use a vibrating quartz crystal. An adhesive surface on the crystal accumulates the dust, and resultant changes in crystal frequency indicate its mass. Together, the two sets of measurements will provide excellent information on dust properties and deposition rates.

The Wheel Abrasion Experiment (WAE) will assess wheel wear (D. Ferguson and J. Kolecki). WAE uses atomically thin metal films deposited on black anodized aluminum strips attached to a rover wheel. A photocell monitors changes in film reflectivity as the rover moves and the surfaces wear. Twice each martian day, all the other rover wheels will be locked stationary while the test wheel alone is spun and allowed to dig into the martian surface. Marked abrasion will indicate a surface composed of hard, possibly sharply edged grains. Lack of abrasion would suggest a somewhat softer surface. WAE results will be correlated with ground simulations to determine which terrestrial materials behave most like Mars dust. This knowledge will enable a deeper understanding of erosion processes on Mars and the role they play in martian surface evolution. All of the above results will be significant to future Mars designs.

Rover electrostatic charging will be controlled by fine, tungsten points mounted on the rover antenna base (J. Kolecki and M. Siebert). Tests and calculations have confirmed the possiblity that the rover will accumulate a large static charge during its surface operations. (the charge is though to occur when the dry martian dust is compacted by the rover wheels.) Once this charge is accumulated, disruptive electrical discharges on our around the rover become possible. Since actual martian conditions are unknown, discharge points have been added to the rover as a precaution. If the rover accumulates electric charge, some, or all of it will be removed to the atmosphere through the discharge points. Atmospheric dust, blowing by the rover, will collect this charge, and eventually return it to the martian surface. Discharge currents through the points are predicted to be non-disruptive.