A pair of palm-sized satellites deployed by the shuttle Endeavour crew on Monday could help pave the way for tiny robotic probes to be stationed on satellites and available for inspections and repairs when equipment problems strike.
The experimental spacecraft, called MEPSI -- for micro electromechanical systems picosatellites -- are the latest test subjects from the Defense Advanced Research Projects Agency's ongoing program to create tiny sensors, thrusters and operational systems for miniature craft called pico satellites.
"You have regular satellites and then micro-satellites, which are smaller, about the size of a breadbox. These pico satellites are about the size of a softball," said Endeavour commander Jim Wetherbee.
Added Clark Nquyen, DARPA program manager: "We're making things that normally would fit into a teacup smaller than 1 centimeter by 1 centimeter."
The MEPSI spacecraft, which are connected by a 50-foot-long tether, measure 4 inches by 4 inches by 5 inches each. The pair were shot into orbit from a special spring-loaded launcher mounted on the side of the payload bay of Endeavour.
"We're just going to film them as they move on up, and then they're going to be transmitting the data back down to the ground," said Endeavour pilot Paul Lockhart in a preflight interview.
MEPSI is expected to operate for at least three days before the satellites re-enter Earth's atmosphere and incinerate. While in orbit, ground tracking stations will monitor MEPSI to see how it is operating.
"We're still developing the technology," said Nquyen, adding that the idea is to develop spacecraft that can inspect and possibly repair faulty satellites.
"The goal for pico satellites in the future is to have them operating and be able to be attached to a regular satellite and then if there are problems with the satellite this little pico satllite can remotely fly around the vehicle and take camera views," said Wetherbee. "Someday in the distant future maybe a smaller satellite (also) will be able to autonomously repair a satellite."
MEPSI spacecraft have flown twice before but never aboard the space shuttle. The previous satellites were launched in February 2000 and September 2001 aboard Air Force expendable Minotaur launchers. Program managers hope a successful third flight will clear the way for future pico satellites to be flown on virtually any shuttle mission.
The spacecraft were built by The Aerospace Corp. of Los Angeles and NASA's Jet Propulsion Laboratory in Pasadena, Calif. The point of the tethering the spacecraft is to make them easier to detect with ground-based radar and to keep the pair within radio range of each other.
"Our other flights have been very successful and we believe this one will be also," said Nquyen.
