Herschel space telescope construction. Engineer looking at a computer representation of the surface of the M1 mirror (upper centre) of the Herschel space telescope. This is being done to check the accuracy of the polished surface of the mirror. 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 with a diameter of 2.4 metres. Photographed at the Opteon optics manufacturing and testing centre, Finland.
Herschel space telescope construction. Photograph. Britannica ImageQuest, Encyclopædia Britannica, 25 May 2016.
quest.eb.com/search/132_1335670/1/132_1335670/cite. Accessed 27 Feb 2017.