NASA GRC NEWS RELEASE 99-41




News Release 99-41



For Release: May 18, 1999



Pam Caswell
(Bus: 216/433-5795)



Lori J. Rachul
(Bus: 216/433-8806)


<h3>Mars Experiments to Look at Best Solar Cells for Dusty Planet</h3> 


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/

# # # 

99-41

	
-end-