News Release 99-41
For Release: May 18, 1999
Lori J. Rachul
Mars Experiments to Look at Best Solar Cells for Dusty Planet
How well can different types of solar cells "stand up" to conditions on a cold and dusty Mars? Two NASA Glenn Research Center experiments, which will help answer that question, have been approved for the Mars Surveyor 2001 Lander mission and will be built as flight hardware.
The Mars Array Technology Experiment (MATE) and the Dust Accumulation and Repulsion Test (DART) are part of the Mars In-Situ Propellant Production Precursor (MIP), which will demonstrate the feasibility of producing oxygen propellant from the Martian atmosphere. MATE and DART will test the capabilities of solar cells to reliably generate electrical power for MIP and other machine activities on the surface of Mars.
Although the Martian atmosphere is very thin (over 100 times thinner than Earth's atmosphere), occasional windstorms raise large amounts of dust into the atmosphere. The dust both absorbs and reflects sunlight and changes the spectrum of the sunlight seen by a solar cell. Worse, as winds calm, dust can settle and accumulate on the solar cells. Over time the settled dust could block more and more sunlight and reduce or even stop the cell's power output. Mars is also very cold, with temperatures near its equator, where the Mars 2001 Lander will be, much like those in Antarctica here on Earth. The life of any Mars mission dependent on dust-blocked, cold-affected cells' power could be short changed.
"Because of the dust, the cold temperatures and the varying spectrum, the best solar cell for our 'gas station on Mars' might be one that we wouldn't consider using in our space solar arrays," said Cosmo Baraona, Glenn project manager for the two experiments.
MATE will measure the solar spectra on Mars and test seven types of solar cells. Each is most responsive to a particular part of the solar spectrum, and each behaves differently at different temperatures.
"We were delighted that the solar cells powering Pathfinder and the Sojourner Rover lasted longer than the mission plan called for, but we don't know if those cells are the best type for longer missions of, say, 5 years. The MATE experiment will help us find the right cells for future long missions on Mars," said David Scheiman, a researcher at the Ohio Aerospace Institute (OAI) and MATE principal investigator.
DART will measure dust particle size, the rate of accumulation and their effects on solar cell output. It will also test two ways to avoid dust accumulation: by slanting the solar cells and by repelling dust with an electrical charge.
According to Dr. Geoffery Landis, a researcher at OAI and principal investigator of the DART experiment, the Mars Pathfinder experience did not tell us whether the Martian dust has an electrical charge. Charged dust particles would stick to solar cell surfaces, much like lint sticks to a pocket comb after it has been rubbed across a piece of wool. "But if the dust is not charged, simply slanting the cells may be a simple way to keep the dust from adhering," he said.
Both experiments will provide data to scientists who will use it to improve computer mathematical models of the Martian atmosphere. With those models, scientists will be able to predict optical conditions at other sites.
The MATE and DART experiments are part of Glenn's continuing effort to provide the power for the future exploration of space and other worlds. The MIP will be aboard the Mars Surveyor 2001 Lander, which is scheduled to launch April 10, 2001, and to land on Mars on January 22, 2002. The MIP demonstration project is managed by Johnson Space Center, NASA's lead center for the Office of Human Exploration and Development of Space. Mars Surveyor 2001 is part of the Mars Surveyor Program, a long-term program of Mars exploration managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, Washington, D.C.
For information about the Glenn Research Center DART and MATE experiments, visit their web site at: http://powerweb.lerc.nasa.gov/pvsee/experiments/2001.html
For more information about the Mars 2001 mission and Mars In-Situ Propellant Production Precursor (MIP), visit its web site at: http://mars.jpl.nasa.gov/2001/
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