With Webb’s first major structural deployments complete and the deployable observatory tower range expanded, we’re taking a step back to learn more about Webb’s sunvisor. Scientist at the Michael McElwain Observatory Project, from NASAThe Goddard Space Flight Center offered these ideas:

“Webb’s telescope and science instruments are ready to go into the shade and you’ll never see direct sunlight again. Use one of Webb’s unique design features Denial It is cooled by a five-layer sunscreen to achieve telescope operating temperatures of 45 K (-380 degrees). F) Huge sunscreen that measures 70 by 47 feet (21 by 14 meters) when deployed, or about the size of a tennis court. The geometry and size of the sunvisor were determined so that the telescope could indicate a field of view covering 40% of the sky at any given time and could be observed anywhere in the sky over a six-month period. This innovative architecture allows Webb’s sensitivity to be limited to a natural sky background (mostly zodiacal light) rather than compromised by the observatory’s thermal brightness, for all wavelengths below 15 microns, during the mission.

“For launch, the sunvisor has been folded like a canopy and positioned in the forward and aft deck structures (UPS). The telescope support structures and sun shield are all mechanically connected to each other and the spacecraft shuttle to fit the Ariane 5 fairing and withstand the dynamic launch environment.”

Upon launch and during his first month in space, on his way to the second Langrange point (L2), Webb will undergo a complex unfolding sequence. Credit: NASA, ESA, CSA, Joyce Kang (STScI)

“There are 50 Major Deployments Which converts Webb from a stored boot configuration to an operational monitor. The sunvisor deployment sequence was initiated by mechanical release to the front and then rear of the UPS and mechanically lowered position. Then the telescope and scientific instruments, mounted in a collapsible turret assembly, were launched and lifted mechanically. There is a thrust flap attached to the rear end of the UPS that is released and positioned, and its function is to balance the solar pressure on the diffuser’s sun visor. Mask covers are released by pulling the film editing hardware out of the way, setting up the system for spreading the brow layers. The median telescopic arms sequentially branch off the spacecraft mount perpendicular to the telescope’s line of sight, pulling the folded stack of layers of sunscreen into the final, but still not kinked, configuration. Finally, each layer of sunscreen is held in place, starting with the layer facing the sun and ending with the layer facing the telescope. The diffused sunscreen begins a rapid deceleration of the telescope and scientific instruments, but heaters on the scientific instruments will be used to control its deceleration and prevent contamination.

“While these steps have been tested and rehearsed operationally at the Mission Operations Center, these activities must be carried out essential to a successful mission. Regards to our team and calm down, Webb!”

— Michael McElwain, Web Observatory Project Scientist, NASA’s Goddard Space Flight Center