Through the looking glass: Technicians check one of the mirrors in the clean room at Nasa's Goddard Space Flight Center in Greenbelt, Maryland. Each of the infrared telescope's 18 hexagonal primary mirrors – which will form a single mirror in space – measures more than 1.3 metres across and weighs approximately 40kg. The segments are made of beryllium coated with gold. The telescope will be capable of peering through clouds of dust to the first galaxies to form after the big bang, and is scheduled for launch in 2018

Photograph: Chris Gunn/NASA