NASA engineers have begun a crucial phase in deploying the James Webb Space Telescope. The engineers have started to tighten the tension in its tennis court-sized sunshield. The stretching of the first three layers of the five-layer sunshield was successful and the final two layers will be deployed today, January 4, the space agency said. A successful deployment of all the five layers is critical for the $10-billion (roughly Rs. 74,525 crore) observatory to remain cool enough to be able to do its job. Once fully stretched, the kite-shaped sunshield will measure 47 feet across and 70 feet long.

The first layer was pulled fully taut into its final configuration Monday afternoon. The engineers took 74 minutes to deploy the second layer and 71 minutes to complete the third. In all, the process to deploy the three layers took around five and a half hours. Being closest to the Sun, these layers would mostly contribute to radiating the heat. The pre-set schedule calls for the deployment to finish by Wednesday.

The sunshield is an important component of the James Webb telescope as it specialises in heat-sensitive infrared observations. When fully deployed, the sunshield will protect the telescope from the Sun’s radiation. It will keep James Webb’s instruments cool at a minimum of -218 degrees Celsius.

James Cooper, NASA’s Webb sunshield manager, based at Goddard Space Flight Centre, said in an official blog post that the sunshield tensioning phase is challenging because there are complex interactions among several components including cables and membranes. “This was the hardest part to test on the ground, so it feels awesome to have everything go so well today. The Northrop and NASA team is doing great work, and we look forward to tensioning the remaining layers.”

The James Webb Space Telescope was launched aboard an Ariane 5 rocket on December 25, 2021. The observatory is expected to take a month to fully deploy nearly 1.6 million kilometres away from Earth and take over observation of the universe from Hubble Space Telescope.