Tiny Technology Powers Microsatellite on Educational Mission
Dec. 6, 2001
by Susan Murphy
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Project Starshine—an international educational program that launches and tracks small satellites—is giving a Rochester Institute of Technology scientist the opportunity to test micropower technology in space for the first time.
Ryne Raffaelle, an RIT physics professor and scientist at NASA’s Glenn Research Center, helped design several tiny power supplies attached to the Starshine 3 satellite. The hollow aluminum microsatellite is part of Project Starshine, involving NASA, the U.S. Navy and Air Force, Lockheed Martin, the Ohio Aerospace Institute and others.
Starshine 3 is important as the first flight testing of a new kind of power source: an integrated micro power supply (IMPS) that combines energy generation and storage—a lithium ion battery and a specially designed solar cell—in one microelectronic device.
The IMPS device provides power from the solar cell when the sun illuminates it, while at the same time charging the battery. The stored energy of the battery can then be used when the satellite passes on the opposite side of the earth away from any sunlight. Providing continuous power is crucial for many satellite systems.
"This is a difficult task when one considers that the Starshine 3 is rotating at five degrees per minute and spends 31 minutes of its 92 minute low-earth orbit in the earth’s eclipse," Raffaelle says.
The microsatellite, measuring only 37 inches in diameter and weighing 197 pounds, required an extremely small power supply. The tiny device Raffaelle helped design to fit the microsatellite is less than 0.3 inches squared and 0.187 ounces and will keep the satellite’s temperature-monitoring system working throughout its three-year orbit.
"Being able to provide a constant power supply with such intermittent illumination is a challenge," Raffaelle says. "In addition, no one has ever tried to recharge a lithium ion battery in space—It’s doing wonderfully. The power supplies are working flawlessly."
The previous Starshine satellites were designed without the power supply and communication system that makes Starshine 3 unique. Thanks to Raffaelle’s integrated micro power supply, school children and amateur radio operators are able to collect and relay data about solar cell performance by downlinking data from the satellite.
Students also are tracking the satellite by using simple digital stopwatches to count how fast the satellite’s 1,500 mirrors reflect flashes of sunlight on days when the satellite is visible. The students then e-mail their stopwatch readings to a project coordinator. Scientists will use the students’ data to determine the effect of solar activity on satellite drag in the earth’s upper atmosphere.
The microsatellite, launched Sept. 29 from Kodiak, Alaska, atop a Lockheed Martin Athena rocket, also is notable as Kodiak’s first non-military application.
To talk to Ryne Raffaelle, contact Susan Murphy at (585) 475-5061 or firstname.lastname@example.org.
For more information about Project Starshine, log onto http://www.azinet.com/starshine.