Launch and commissioning of the James Webb Space Telescope

[3] The telescope was confirmed to be receiving power, starting a two-week deployment phase of its parts[4] and traveling to its target destination.

[3] The telescope was confirmed to be receiving power, starting a two-week deployment phase of its parts[4] and traveling to its target destination.

[1][14] Starting 31 minutes after launch, and continuing for about 13 days, JWST began the process of deploying its solar array, antenna, sunshield, and mirrors.

[28][29] The mission was designed to give ground controllers flexibility to change or modify the deployment sequence in case of problems.

Power usage was greater than that supplied by the solar arrays and this resulted in increased drawdown of the telescope's batteries and higher than expected voltage.

To ensure power delivery would be sufficient for spacecraft and science operations, the solar panels were reset and duty cycles were optimized to account for the real world conditions observed including array temperatures.

[33] At 7:50 p.m. EST on 25 December 2021, about 12 hours after launch, the telescope's pair of primary rockets began firing for 65 minutes to make the first of three planned mid-course corrections.

This deployment precedes the actual unfolding and extension of the delicate shield membranes, which are pulled out of the pallets by telescoping beams in a subsequent step.

[36][37] On 29 December 2021, controllers successfully extended the Deployable Tower Assembly, a pipe-like column, which moved apart the two main segments of the observatory, the telescope with its mirrors and scientific instruments, and the "bus" holding electronics and propulsion.

Deployment created the needed distance between the JWST segments to allow extreme cooling of the telescope and room for the sunshield to unfold.

First, commands deployed the aft "momentum flap", a device that provides balance against solar pressure on the sunshield, saving fuel by reducing the need for thruster firing to maintain Webb's orientation.

[41][42] On 31 December 2021, the ground team extended the two telescoping "mid booms" from the left and right sides of the observatory, pulling the five sunshield membranes out of their folded stowage in the fore and aft pallets, which were lowered three days earlier.

[43] Deployment of the left side boom (in relation to pointing direction of the main mirror) was delayed when mission control did not initially receive confirmation that the sunshield cover had fully rolled up.

[33] After resting on New Year's Day, the ground team delayed sunshield tensioning one day to allow time to optimize the observatory's array of solar panels and to adjust the orientation of the observatory slightly to cool the slightly hotter-than-expected sunshield deployment motors.

[48] On 5 January 2022, mission control successfully deployed the telescope's secondary mirror, which locked itself into place to a tolerance of about one and a half millimeters.

[51][52][53] On 24 January 2022, at 2:00 p.m. EST,[54] nearly a month after launch, a third and final course correction took place, inserting JWST into its planned halo orbit around the Sun–Earth L2 point.

[59][57] Commissioning is complicated by the fact that the telescope's performance and precise shapes of some components will also change microscopically as it continues to cool.

[a][64][65] (HD 84406 is bright and easily identified, will stay in view for the entire 3 months of commissioning, and is in part of the sky with fewer other stars.)

[62] With the mirrors now positioned for almost correct images, they must be fine tuned to their operational accuracy of 50 nanometers, less than one wavelength of the light that will be detected.

A technique called dispersed fringe sensing compares images from 20 pairings of mirrors, allowing most of the errors to be corrected ("Coarse Phasing"), and then the same technique is used with special optical elements to introduce ±4 and ±8 waves of defocus to each segment's image, allowing detection and correction of almost all remaining errors ("Fine Phasing").

[62] In preparation for alignment, NASA announced at 19:28 UTC on 3 February 2022, that NIRCam had detected the telescope's first photons (although not yet complete images).