The Most Sophisticated Mirror in the Universe
Hank summarizes the five reasons why infrared telescopes were supposed to be impossible to build, and then describes how a team of scientists and engineers overcame those obstacles to build the James Webb Space Telescope.
Many thanks to Scott Willoughby and the entire team at Northrop Grumman for the tour.
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A note re: gold from Dr. Amber Straughn of NASA - “Gold is not the only “reddish” elemental metal (Copper is even more reddish) and other metal alloys are reddish or yellow (e.g., bronze, brass). The point is simply that gold is an excellent reflector of ALL the wavelengths of light that Webb is designed to see—from 0.6 microns out to 27 microns. Gold happens to look gold to us because it reflects blue light poorly, but this doesn’t matter because Webb doesn’t see light shorter than visible red. Silver is also an excellent reflector of IR, but it’s not as good as gold at ALL the wavelengths that Webb will observe.”
And re: the mirror - while the individual mirror segments have been completed, the full-size mirror has not yet been fully assembled and tested. And though “polishing a 6.5m continuous mirror is incredibly difficult, it is not technically “impossible.” In fact, a team at REOSC in France and at the mirror lab at U of AZ have been casting and polishing 8.4m optical primary mirrors for years now. But making the mirror in segments, in addition to making it deployable, makes polishing the mirror an easier-to manage process—basically polishing 18 small mirrors vs. one huge one, especially considering it is a mirror for an IR telescope operating at cryogenic temperature and enables easier transportation during the polishing and construction process (it’s really difficult, time-consuming and expensive to move a monolithic 8.4m primary—akin to moving the whole Webb observatory).”