The Materials Adherence Experiment (MAE) was a material science experiment conducted between July 4, 1997 and August 12, 1997 during
NASA's ''
Mars Pathfinder
''Mars Pathfinder'' (''MESUR Pathfinder'') is an American robotic spacecraft that landed a base station with a roving probe on Mars in 1997. It consisted of a lander, renamed the Carl Sagan Memorial Station, and a lightweight, wheeled robot ...
'' mission.
This was a joint experiment between NASA and the Jet Propulsion Laboratory at the California Institute of Technology
that consisted of a small module mounted to
''Pathfinder's'' rover
''Sojourner'' that examined the effects of
Martian surface dust on
solar cell
A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon. s.
[
]
Purpose
Using solar power on the Martian surface is challenging because the
Martian atmosphere
The atmosphere of Mars is the layer of gases surrounding Mars. It is primarily composed of carbon dioxide (95%), molecular nitrogen (2.8%), and argon (2%). It also contains trace levels of water vapor, oxygen, carbon monoxide, hydrogen, and no ...
has a significant amount of dust suspended in it.
In addition to blocking sunlight from reaching Mars's surface, dust particles gradually settle out of the air and onto objects. As ''Pathfinder'' was NASA's first Mars surface mission to be solar-powered, the effect of Martian dust settling on solar cells was not well understood before the mission.
It was predicted at the time that dust particles in the Martian atmosphere would settle on the solar cells powering ''Pathfinder'', blocking sunlight from striking them and slowly causing ''Pathfinder'' to lose power. Since knowing how the settling of dust out of Mars's atmosphere would affect solar cell performance would be critical to subsequent solar-powered missions on Mars, the MAE was included aboard the ''Sojourner'' rover to measure the degradation in performance of a solar cell as dust settled.
Design
The MAE, which was located on the front left corner of the solar array,
consisted of a small
gallium-arsenide
Gallium arsenide (GaAs) is a III-V direct band gap semiconductor with a zinc blende crystal structure.
Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circ ...
solar cell mounted underneath a removable glass cover plate. As the mission progressed, atmospheric dust would settle on the glass cover plate, blocking increasingly more sunlight from striking the solar cell, causing it to produce less power. Throughout the mission, the glass cover plate was occasionally rotated away from the solar cell, removing the light-blocking effects of the dust. Sensors measuring the difference in power output of the solar cell before and after the cover plate was removed indicated how quickly the solar cell was losing its ability to produce power, and by extension, how quickly dust was collecting on the cover plate.
The rotating actuator used to move the glass cover plate away from the solar cell marked the first use of a multi-cycle
shape memory alloy
In metallurgy, a shape-memory alloy (SMA) is an alloy that can be deformed when cold but returns to its pre-deformed ("remembered") shape when heated. It may also be called memory metal, memory alloy, smart metal, smart alloy, or muscle wire.
P ...
in a space application.
Due to the high level of UV radiation on the surface of Mars, it was important that the glass that covered the solar cell would not darken. For this purpose
Suprasil was chosen.
Results
The MAE recorded a 2% obscuration due to dust on its first day of operation, probably caused by dust kicked up locally by ''Pathfinder's'' airbag being retracted.
Measurements taken by the MAE at local noon for the first 24 days of ''Pathfinder's'' operation on Mars showed that atmospheric dust obscured the test solar cell at a rate of 0.28% per day.
[ This degradation rate was about the same regardless of whether ''Sojourner'' was moving or stationary.] Measurements taken at local 2pm showed a slightly higher obscuration rate over the first 20 days of the mission, at 0.33% per day. These findings were consistent with the decline in power output of the solar cells on ''Sojourner'' and the ''Pathfinder'' lander, which indicated a dust accumulation rate of 0.29% per day, and fairly close to the value predicted before ''Pathfinder'' landed (0.22% per day).
See also
* Exploration of Mars
The planet Mars has been explored remotely by spacecraft. Probes sent from Earth, beginning in the late 20th century, have yielded a large increase in knowledge about the Martian system, focused primarily on understanding its geology and habi ...
* Martian soil
Martian soil is the fine regolith (a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock) found on the surface of Mars. Its properties can differ significantly from those of terrestrial soil, including its to ...
* Mars Environmental Dynamics Analyzer (planned atmospheric and dust experiment for the Mars 2020 rover)
*Cleaning event
__NOTOC__
A cleaning event is a phenomenon whereby dust is removed from solar panels, in the context of exploration and science rovers on Mars, supposedly by the action of wind. The term cleaning event is used on several NASA webpages; general ...
References
;Notes
;Bibliography
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External links
Overview of MAE results on original Mars Pathfinder mission site
National Space Science Data Center technical discussion of MAE
{{Mars Pathfinder
Mars Pathfinder
1997 in science
Exploration of Mars
Missions to Mars
Spacecraft instruments
Solar power and space