Setting up NASA's James Webb Space Telescope's secondary mirror in space will require special arms that resemble a tripod. The secondary mirror support structure will unfurl in space to about 8 meters (26.2 feet) long once it is deployed. Engineers inside the world's largest clean room at NASA's Goddard Space Flight Center in Greenbelt, Maryland worked on the engineering test unit or "Pathfinder," for the James Webb Space Telescope. Webb’s Pathfinder acts as a spine supporting the telescope primary mirror segments. The Pathfinder is a non-flight prototype. To install the mirrors onto the center structure, the pathfinder must be first be over-deployed, that means engineers must secure two of the struts against the wall so they have plenty of room to work.