May 18, 2024

James Webb Space Telescope Commissioning Set to Begin

When NIRCam reaches 120 kelvins (around -244 degrees Fahrenheit, or -153 degrees Celsius), Webbs optics team will be prepared to start meticulously moving the 18 primary mirror sections to form a single mirror surface area. The team has actually chosen the star HD 84406 as its target to start this process. It will be the very first item NIRCam “sees” when photons of light struck the instruments powered-on detectors. The procedure will basically develop a picture of 18 random, blurred points of light. For the first couple of weeks of mirror alignment, the group will keep the instrument trained on the star while they make tiny modifications to the mirror sectors; eventually that collection of 18 blurred dots will end up being a concentrated picture of a single star. Cooling of the telescope and instruments will also continue over the next month, with the near-infrared instruments eventually reaching 37-39 kelvins. The cryocooler will cool MIRI to 6 kelvins in the following months.

By NASA
January 31, 2022

Credit: NASAs Goddard Space Flight
Following Webbs arrival at its orbital destination around Lagrange Point 2 (L2) on January 24, the mission operations team started working its way through a crucial series of steps: powering on all the science instruments, shutting off heating systems to begin a long cooldown process, and ultimately catching the first photons on Webbs main electronic camera to allow a months-long alignment of the telescope.
While the MIRI instrument and some instrument elements were powered on in the weeks after Webbs December 25 launch, the group didnt complete switching on the remaining 3 instruments– NIRCam, fgs/niriss, and nirspec– until the previous couple of days.
The mission operations teams next significant step is to turn off instrument heating systems. The heating units were needed to keep crucial optics warm to prevent the danger of water and ice condensation. As the instruments meet pre-defined requirements for overall temperature levels, the group is shutting down these heating systems to permit the instruments to reboot the months-long process of cooling to final temperatures.