Herschel space telescope construction. Technicians preparing the M1 mirror (centre) of the Herschel space telescope for optical testing in a controlled environment. Here a cover (white) has been placed over the mirror to protect it from damage whilst being moved. With its primary mirror measuring 3.5 metres in diameter, the European Space Agency's Herschel telescope is the largest space telescope ever built; larger than the Hubble telescope which has a diameter of 2.4 metres. Photographed at the Liege space centre (CSL), Belgium.
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