By John McHale
REDONDO BEACH, Calif. - Engineers at TRW Inc. used gallium arsenide germanium (GaAs/Ge) solar cells to reduce weight and boost power available to NASA`s Earth Observing System AM-1 (EOS AM-1) spacecraft.
"The power produced by 190 gallium arsenide cells is equal to that produced by 380 silicon cells," explains Mike Herriage, EOS AM solar array program operations manager at TRW Space & Electronics Group in Redondo Beach, Calif. Gallium arsenide is four to five times more expensive than silicon.
TRW engineers built a high-power array that is 20 to 30 percent smaller and 20 to 25 percent lighter than a conventional array using silicon solar cells.
The new array`s small size and weight enables NASA technicians to save money by launching it on an Atlas 2 rocket rather than a Titan 4, Herriage explains.
The array uses multi-junction gallium indium phosphate on top of GaAs/Ge photovoltaic solar cells for an improved power-to-mass capability over standard cells.
The 485-square-foot solar array is as thin as several sheets of paper and generates 25 percent to 35 percent more energy per pound than solar arrays made with silicon cells.
The 160-pound solar array is based on a prototype lightweight, flexible blanket solar array TRW engineers developed for the Jet Propulsion Laboratory`s Advanced Photovoltaic Solar Array program, which was sponsored by NASA`s Office of Advanced Concepts and Technology.
To meet future spacecraft needs, the EOS AM-1 solar-array blanket design is expandable to more than 20 kilowatts in a two-wing configuration.
Designers can reduce solar array mass with thin-film photovoltaic cells, flexible blanket substrates, and composite support structures. They can boost solar array efficiency by using new photovoltaic cell materials and solar concentrators that intensify the incident sunlight.
The array will provide power for the EOS AM-1 spacecraft on its mission to gather information about clouds, volcanoes, and Earth`s land surface. EOS AM-1 is scheduled to be launched from Vandenberg Air Force Base, Calif., in June 1998.
EOS satellites are part of NASA`s Mission to Planet Earth (MTPE), a long-term program to monitor natural and human-induced changes to Earth`s climate and environment.
TRW also supplies conventional, rigid panel solar arrays for other MTPE missions, including the Total Ozone Mapping System spacecraft, the Tropical Rainfall Monitoring Mission spacecraft and the TRW-built EOS PM-1 spacecraft.
Large gallium arsenide germanium solar cells from TRW are reducing weight and boosting power on NASA`s Mission To Planet Earth program.
