Space Telescope

The James Webb Space Telescope has a series of mirrors to get the light from the universe into the observatory's cameras. After the light reaches the primary mirror, it is then bounced up 25 feet to the secondary mirror. This much smaller mirror is deployed using three arms, or struts.

One of the mechanical integration engineers at NASA's Goddard Space Flight Center in Greenbelt, Maryland, talks about how the mirrors will unfold. "We deploy three struts that are much like a tripod, and the secondary mirror will sit above the backplane."

Secondary mirror being worked

Because the Webb telescope is too large to fit into a rocket in its final shape, engineers have designed it to unfold like origami after its launch. That unfolding, or deployment, includes the mirrors on the observatory, too. The segmented primary mirror collects light from the cosmos and directs it to the secondary mirror, which sends it additional smaller mirrors before it reaches the cameras and spectrographs.


The three struts are almost 25 feet long, yet are very strong and light-weight. They are hollow composite tubes, and the material is about 40-thousandths of an inch (about 1 millimeter) thick. They are built to withstand the temperature extremes of space.


The Webb telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.