How Webb Stays in Focus

One of the most difficult challenges when assembling a telescope is aligning it to optical precision. If you don’t do it correctly, all your images will be fuzzy. This is particularly challenging when you assemble your telescope in space, as the James Webb Space Telescope (JWST) demonstrates.Unlike the Hubble Space Telescope, the JWST doesn’t have a single primary mirror. To fit in the launch rocket, it had to be folded, then assembled after launch. For this reason and others, JWST&r