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.
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.
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.
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.
You may also see an overview of the contributions
made by the Lewis Research Center to the Pathfinder mission, written
by the folks at LeRC.