The James Webb Space Telescope (JWST), a collaboration between NASA, ESA, and the Canadian Space Agency, underwent a process known as “fine phasing” to improve its vision from a distance of a million kilometers away.
The JWST, launched in December 2021, is the most powerful space telescope ever built. It is designed to capture the universe’s earliest light, analyze the atmospheres of exoplanets, and perform other vital astronomical tasks. Unlike the Hubble telescope that operates in the visible and ultraviolet range, JWST works in the infrared range.
The JWST’s primary mirror, made up of 18 hexagonal segments, is more than twice the size of Hubble’s mirror. However, due to its size, the mirror had to be folded up for launch and then unfolded in space. This presented a challenge as each segment needed to be precisely aligned to function as a single mirror.
To achieve the necessary alignment, a process known as “fine phasing” was used. This involved capturing starlight with the telescope’s Near Infrared Camera (NIRCam), which was then analyzed by the onboard computer. The computer then calculated the necessary adjustments to the mirror segments to achieve the desired alignment. This process was repeated several times over a period of weeks to achieve the final configuration.
The first images captured by the JWST, known as a “segment image,” were blurry because the segments were not yet properly aligned. The images improved as the fine phasing process was carried out, with the final image displaying a single, sharp star.
The JWST also underwent a “wavefront sensing and control” (WFSC) process, a complex operation that used NIRCam to capture a series of images with each mirror segment slightly out of alignment. These images were then combined to create a “wavefront map,” which provided information about the mirror’s shape and alignment.
The WFSC process is critical to ensure the telescope’s performance throughout its mission. This is especially important given the telescope’s distance from Earth, which makes any kind of repair mission impossible. The successful completion of the fine phasing and WFSC processes marks a significant step towards the JWST becoming fully operational.
In conclusion, the fine phasing and WFSC processes were crucial in improving the vision of the JWST. This will enable the telescope to carry out its mission of capturing the universe’s earliest light and analyzing the atmospheres of exoplanets. The JWST is expected to revolutionize our understanding of the universe, building on the work of its predecessor, the Hubble Space Telescope.