Radiation test is goal of UK-built Galileo satellite
The first part of Europe’s Galileo satellite navigation system was launched between Christmas and New Year, on a spacecraft made by Surrey Satellite Technology (SSTL).
“For us it is a big spacecraft, over 600kg,” Surrey’s Dr Craig Underwood told Electronics Weekly. “This is the first demonstration of our new ‘bus’.”
Bus is the space industry term for the chassis, propulsion and navigation parts which together carry a payload through space. This one has been designed for medium Earth orbit (MEO 26,000km) and geostationary (36,000km) use. Previously SSTL has only made small low Earth orbit (LEO) satellites.
Called Giove-A, the craft is one of two which are there to test Galileo principles. The other is Giove-B developed and built by Galileo Industries with UK-based EADS Astrium building the payload.
Giove-A amongst other things will measure radiation levels which are considerably higher than LEO levels at Galileo’s MEO – just above that of the US-owned GPS constellation (19,000km).
Underwood, who is actually director of engineering teaching at SSTL’s owner, the University of Surrey, lead development of the on-board radiation instrument. “We are checking the veracity of radiation models,” said Underwood.
Max Meerman, director of research at SSTL, is also interested in radiation: “We don’t know what the space environment is, no satellite has been there before. You can’t model radiation without input parameters.”
Meerman also pointed out that only last week researchers elsewhere discovered new particle interactions within the Van Allen Belt enclosing Galileo’s proposed orbit.
With the environment in mind, Giove-A has extra radiation shields. “Essentially; we went around with lead, and lots of 2mm aluminium has changed to 5 or 10mm,” said Meerman. “There is still a lot of COTS on board, with appropriate shielding,” he added.
SSTL is known for its judicious use of COTS (commercial, off-the-shelf) hardware in its satellites to reduce cost and time-to-launch.
This said, the main processor on Giove-A is ESA’s 695 radiation-tolerant design instantiated in a rad-hard FPGA, said Meerman.
Giove-A and B will not be part of the final 30 satellite Galileo constellation.