ESA’s Billion Star Surveyor: UCL’s contribution

On Thursday 19 December at 09:12 GMT, a satellite designed to unlock the secrets of the birth and evolution of the Milky Way Galaxy will be launched by the the European Space Agency. UCL's Mullard Space Science Laboratory has played a major part in the satellite - named Gaia - for 12 years, developing the instrument that will measure the speed, temperature, size and age of over a billion stars in our galaxy. Gaia's mission is to slowly scan the sky, rotating every six hours, and survey the whole sky some hundred times in its six year mission. It has two extraordinarily stable telescopes, each focussing on the same huge array of 106 electronic detectors, the biggest ever either launched into orbit or on any Earth-based telescope. The angles between the stars from each telescope will be measured precisely, and with more than a billion stars, the whole mesh of angles can be number-crunched to calculate the position of each star a thousand times more accurately than currently possible. Professor Mark Cropper, from the Mullard Space Science Laboratory, who has worked on Gaia from its inception, said: "This is an astonishing step up in accuracy. To give an example, Gaia will measure the difference in position of one side of a human hair compared to the other side of it - in Paris, as viewed from London." - Measuring the Milky Way.