Linux May Enter Orbit
Linux may be an operating system synonymous with a flightless bird, but if some Sydney, Australia research students have their way, it could be orbiting the earth controlling a space satellite within two years.
The Bluesat microsatellite is a joint project of the Mechanical, Electrical, Telecommunications, and Computer Systems engineering departments at the University of New South Wales. The students have spent several years designing a 10-kilogram microsatellite, including its structure and flight computer. Bluesat is scheduled for takeoff in November 2005.
Small Enough for Space
The project's chief technical officer, Ashley Butterworth, says he is unaware of any Linux in space, adding that most amateur radio satellites are too small to have a computer.
"What we've got is fairly powerful for a satellite computer so we may put Linux in space," Butterworth says.
"Our biggest problem is the small amount of power available so we need to be careful with what we run on it. Also, we have to trust the software explicitly because if something happens to the software the satellite can shut down."
Butterworth says that because Linux is open source, the team can review all the code and verify that it works and can "strip it down" and use the L4 microkernel. The team is designing and building the satellite's computer. It comprises a StrongARM SA 1100 embedded system and the team designed the printed circuit board.
"We can port the Linux subsystem and what is missing from L4 to the StrongARM processor," he says. "The L4 microkernel will handle the lower-level processes and functionality from Linux, such as the mass storage device driver, will be ported to it."
Butterworth says the computer can be adversely affected by radiation so error detection and correction (EDAC) is required. There's also the possibility of "shaking the computer to death" during take off, so the team of 15 undergraduates and one postgraduate must ensure the board is mounted properly and flash memory is used rather than hard disks.
Due to this lack of storage capacity, all data will be beamed to earth during orbit.
The Mars Exploration Rovers, which were delivered to the planet by the Mars Pathfinder earlier in 2004, ran an original operating system that had particular emphasis on remote control.
Backup in Development
Not content with just having Linux and L4 available, the team is also developing its own operating system for Bluesat, aptly coined BluesatOS, as part of a thesis for one of the students.
"BluesatOS will be a small operating system that gives us just what we need, so if Linux crashes we can fall back on that," he says.
"We will probably use ours as the primary operating system but we have the ability to upload an operating system to the satellite," Butterworth adds. "The error detection system will reboot the computer to one of the other operating systems so we can go up there with a few on board."
Bluesat is an amateur radio communications satellite, which will act like a "flying FTP server" so people can share information. The satellite will also conduct a UV radiation shielding experiment to test the suitability of a lightweight material which could be used for space suits.
"We get yearly funding from three schools in the faculty of engineering and we go out and find sponsors for supplies and other essentials," Butterworth says. "We are now seeking funding for the launch, which will cost about half a million dollars. Also, when people graduate they leave the project, so we could do with a few PhD scholarships to help retain skills."