A €450 million mission to measure the precise location of stars in the Milky Way may be threatened by bursts of radiation from the Sun, Physics World is reporting.

Gaia, as the spacecraft is known, is the latest in a series of astrometry satellites which will measure the positions of millions of stars in the galaxy. That might sound easy, given that ground-based surveys like the Sloan Digital Sky Survey have done the same with around a million galaxies, but it’s not. Stars in the Milky Way are generally too close to be measured using the traditional redshift method used to chart distant galaxies. Instead, Gaia will rely on relative motion, brightness and parallax (the slight change in apparent position of nearby stars at different times of year) to figure out how far away many of these stars are.

That is, if our nearest star doesn’t ruin everything. The Sun kicks out a lot of high-energy protons that can get caught in Gaia’s CCD cameras. On a normal mission, these extra protons aren’t much of a problem, but they could cause Gaia to misjudge the position of the stars it is trying to map. Gaia will be placed at the L2 point, a gravitationally stable orbit millions of miles from earth, so it won’t have our atmosphere to protect it from the radiation. As if it wasn’t all bad enough, the spacecraft is scheduled to launch in 2012, just as the sun approaches the peak of its 12 year solar cycle.

So what can be done? Apparently not much, according to the Physics World article. The project is too far along for any radical redesign, and anyway, there’s not much that can be done to shield from high-energy protons. The scientist’s only hope is to calibrate the spacecraft in such a way as to discount the noise from the Sun. Not everyone is convinced that the European Space Agency has handled things well, though. Gaia’s former project scientist, Michael Perryman, apparently resigned two years ago over the radiation worries.

Gaia researchers will continue to conduct tests of the satellite’s CCD until 2011. Then they’ll get it ready to fly.

Credit: ESA