NASA Reaches Milestone with James Webb Space Telescope Mirror Calibration

Where once it was 18, now there is only one. The James Webb Space Telescope is currently hanging in space at the Earth-Sun L2 Lagrange point, where it will remain for the rest of its mission. Before it can get around to doing any science, NASA needs to calibrate the instruments and adjust the 18 mirror segments. Initially, each segment created its own image, but NASA reports that they have completed the calibration of James Webb Space Telescopes' mirrors so that they all focus on the same place. 

The James Webb Space Telescope (JWST) is the successor to Hubble, which has been in operation for over 30 years now. As the aging observatory is short of redundant systems, Webb is completely new, and the launch of the textbook means that it can work for as long as 20 years. Its position about one million miles away means that the telescope's instruments remain extremely cold, which is ideal for those between infrared observations that will distinguish JWSTs from each other. Getting this far was a nerve-wracking process for a world that has seen the telescope take shape for the past 20 years - it collapsed inside an Ariane 5 rocket and there were hundreds of potential wrong points in the origami-like development process. 

The last element of the expansion is to get the primary mirror configured, which is why there is only one image of the star HD 84406 below instead of 18. Unlike Hubble, which had a single parabolic mirror, Webb has a reflector in Korsch -style. of adjustable segments. The first image from Webb showed the guide the star 18 times without rhyme or reason. Then NASA identified the position of each mirror segment and began pushing them in the right direction. Through this process, the image is directed from each mirror to the same place on the sensor, giving a single stacked image. 

However, this is not the end of the calibration process. The segments are now in a fairly approximate orientation, but close enough are only counted in horseshoes and hand grenades. Astronomy, not so much. In its current state, Webb's primary mirror functions as 18 small telescopes instead of a large one. Then the team will start adjusting each segment and adjusting them until the variation is less than the wavelength of the light. This process is called rough phasing, and it is the fourth of seven steps to clear the observatory's mirror. 

So far, everything has flowed on, a welcome departure from Webb's time on the ground when it seemed like everything that could go wrong did. With all the delays, Webb ended up costing $ 10 billion. If the rest of the assignment goes as well as the deployment, it will be more than worth the cost.