- The Gaia space telescope is seeing the light - too much of it (Image: ESA/ATG medialab; background: ESO/S. Brunier)
- dn26734-1_300[1].jpg (9.9 KiB) Viewed 2804 times
Gaia was launched in December 2013 to map the Milky Way in unprecedented detail using a 1.5 gigapixel camera to take pictures of a billion stars. But in July last year, ESA revealed that too much light was entering the telescope. This will delay the release of scientific data, so ESA set about diagnosing the problem.
Now ground tests have determined that the most likely cause of the surfeit of light is loose fibres around the edge of Gaia's 10-metre-wide sunshield, which is designed to protect the spacecraft's delicate instruments from the sun's heat.
No quick fix
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
These fibres were spotted on Gaia before launch, but cutting them off was considered too risky, because that could allow small particles to enter the spacecraft. Another option, taping them down, was also ruled out because the increased stiffness could prevent the sunshield from unfolding.
The stray light shouldn't affect measurements of the galaxy's brightest stars, says Gaia science team member Anthony Brown at the Leiden Observatory in the Netherlands, but it will double the expected errors on most of the stars in the Milky Way, which are much fainter.
In particular, this will make it harder to measure their velocity through space. "It's a shame, but not a showstopper," says Brown, who adds that Gaia has already collected more than 4 billion measurements. "We have already collected more spectra of stars than have ever been detected on the ground since we started doing astronomy."