Peek At The James Webb Telescope Before It Peers Into Forming Galaxies
A big, beautiful mirror turns around to say hello
It’s still on Earth for the next two years, but the James Webb Space Telescope turned around to face the world this week, as it moved into position for preliminary optics testing. Once it’s launched, JWST will study galaxy, star and planet formation in the universe using infrared wavelengths. For now, you can spy on the cleanroom at NASA’s Goddard Space Flight Center in Greenbelt, Maryland where JWST is hanging out for the next few months, via the Webb Cam, here.
For the past two months, during final levels of assembly, its big, shiny face of mirrors has been facing away from the viewing gallery, JWST senior engineer Mike Menzel tells Popular Science, “It’s a really beautiful sight.”
Webb’s 18 sections of ultra-lightweight beryllium, making up its 21-foot-wide mirror were assembled in February 2016 at Goddard, and the Webb Cam has been following its construction progress ever since. At the end of the year, Webb moves to Johnson Space Center in Houston and then a Northrop Grumman-led team will take over, developing the deployable sunshield and system integration.
The waves emanating from the center aren’t beacons from another dimension, but reflections of the room on the telescope’s mirrors:
For the next few weeks, the JWST will undergo interferometer measurements and testing, making sure the mirror holds its shape through the extreme sound and vibrations at launch. Each of the segments have been tested separately, but now that the whole mirror is assembled, it’s time to test again. “This’ll be the first data we’ll have of the overall primary mirror… This’ll be the start of proving that each of the 18 segments work together,” Menzel says. At JSC, it’ll undergo more of the same vibrations, plus temperature exposure tests, making sure it hold shape at 50 degrees above absolute zero.
For those tuning in on the Webb Cam, it’ll be difficult to see that anything’s happening. Webb soon turns back around to face the interferometer instrument on a tower six to eight meters away.
After narrowly escaping budget cuts in 2011, the telescope is still on schedule for an October 2018 launch date, according to NASA’s latest update report. “The most visually appealing hardware is the telescope itself, which is marked by a high-reflectivity, very thin, gold coating on the primary mirror segments and the secondary mirror,” writes Observatory Project Scientist Mike McElwain. In other words, it’s very, very pretty.
Correction 10/7 9:15 a.m.: A previous version of this article mis-stated the temperature at which Webb would be exposure tested at JSC.