More on the James Webb Space Telescope

Testing of the James Webb Space Telescope mirrors in the X-ray and Cryogenic Facility (XRCF) here finished just before Christmas, so what’s next? Some of the planned tests have to include all the unfolding that will take place after launch in the extreme cold of space. The mirrors were tested to -379 degrees F, so I’d expect the same of the different mechanisms onboard the telescope.

I found this animation of the deployment, which unfortunately does not have a voiceover of what’s happening. The telescope will be launched in an Ariane 5, and the sunshield alone is the size of a tennis court.


Here’s the play-by-play: first, the solar array unfolds, then the high-gain antenna points to Earth. The two sunshield pallets unfold, allowing the mirror assembly to move away from the “spacecraft bus”, which holds all the avionics and propulsion systems. These generate heat, so they stay on the other side of the sunshield, so the optics and the Integrated Science Instrument Module can stay as cold as possible. (The colder, the better with an infrared telescope.) The sunshield stretches to the sides, and then the five layers separate (and yes, it is pink on one side, just as it’s depicted). The secondary mirror moves into place, and the six folded primary mirror segments swing forward to align with the other 12 segments. The folded down bit away from the mirror is the Momentum Trim Tab, which balances the pressure caused by photons hitting the sunshield. And there you have it, one humongous infrared telescope, ready to peer into the corners of the universe.

You can also take an interactive tour of the telescope here.