Since its launch on 25 dec,2021, space enthusiasts have been eager to know if the JWST’s sunshield, that designed to protect sensitive instruments on board, would be used to perfection. To rightly replace of mighty Hubble, the James Webb Space Telescope must overcome its 344 potential points of failure and deploying the sunshield is a major achievement.
As detailed by NASA in its press release, together 5 thin sheets of plastic will provide a sun protection factor (SPF) of around 1 million. In terms of energy, this will reduce the 200 KW of solar energy received by the telescope to just a fraction of a watt & help keep the temperature of on-board instruments at 380 ° F below zero (233 ° C in below zero) so that pick up weak infrared light from far away.
As with all things with James Webb Space Telescope, deployment of sunshield was no easy task. To begin, at 21.3m (70ft), the shield is the size of a full-size tennis court and had to be neatly folded & wrapped to fit inside Ariane 5 rocket that launched the telescope in space. Deployment began 3 days after launch & continued over 8 day period.
The sunscreen had to be un-folded first & then pulled-taut. During that time, 139 of 178 release mechanisms on telescope were involved, along with 70 hinge assemblies, 8 deployment motors, around 400 pulleys & 90 cables with a length of around 400 m, the press release said.
The deployment was originally scheduled for 6 days, but NASA staff took a break on New Years weekend as some continued to make changes based on data received from spacecraft, The Verge reported. .
The telescope’s solar arrays were generating limited power, but a re-balancing of arrays seems to have solved the problem. The motors used to pull the shield were also running at higher temperatures than expected, so NASA engineers reoriented the spacecraft just enough to keep sunlight from hitting them, after which motors pulled sunshield into its position, The Verge said in its report.
The deployment of the shield that will protect the spacecraft not only from the sun, but also from the light & heat from Earth and its moon marks the completion of up to 75% of single point failures in mission, reported The Verge. The deployment phase is still about five and a half months away, with the primary & secondary mirrors, telescope optics alignment, & calibration of instruments having to be completed before the first image can be received.
In the meantime, the only solace is that the telescope was perfectly launched by the Ariane 5 rocket & its onboard fuel is enough to keep it running for 10 years or more.