A stray thread on a shirt is a mild nuisance, but dangling fibres on a spacecraft are a more serious issue. The European Space Agency鈥檚 Gaia telescope has loose fibres that are letting . This will double the errors on most of its measurements of stars.
Gaia was launched in December 2013 to map the Milky Way in unprecedented detail using a 1.5聽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鈥檚 10-metre-wide sunshield, which is designed to protect the spacecraft鈥檚 delicate instruments from the sun鈥檚 heat.
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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鈥檛 affect measurements of the galaxy鈥檚 brightest stars, says Gaia science team member 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. 鈥淚t鈥檚 a shame, but not a showstopper,鈥� says Brown, who adds that Gaia has already collected more than 4聽billion measurements. 鈥淲e have already collected more spectra of stars than have ever been detected on the ground since we started doing astronomy.鈥�
