The European Space Agency's Gaia space telescope has loose fibres that are scattering too much light into its giant camera, making it harder to map the Milky Way.
Gaia was launched in December 2013 to map our Milky Way galaxy in unprecedented detail using a 1.5 gigapixel camera to take pictures of a billion stars.
However, ESA found that too much light was entering the telescope.
Ground tests have now determined that the most likely cause of too much 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, 'New Scientist' reported.
The stray light shouldn't affect measurements of the galaxy's brightest stars, said 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.
This will make it harder to measure their velocity through space.
"It's a shame, but not a showstopper," said Brown, adding that Gaia has already collected more than 4 billion measurements.
The 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.
