Webb Sunshield Tensioning To Begin Tomorrow
 
Work on the deployment of Webb’s sunshield mid-booms went late into the night yesterday. Webb mission management decided this morning to pause deployment activities for today and allow the team to rest and prepare to begin Webb’s sunshield tensioning tomorrow, Sunday, Jan. 2. That deployment is still expected to take place over at least two days.
 
This will likely affect the full timeline for Webb’s deployment. The timeline will be updated as major deployments resume.

Deployment Timeline Adjusted as Team Focuses on Observatory Operations
 
Taking advantage of its flexible commissioning schedule, the Webb team has decided to focus today on optimizing Webb’s power systems while learning more about how the observatory behaves in space. As a result, the Webb mission operations team has moved the beginning of sunshield tensioning activities to no earlier than tomorrow, Monday, Jan. 3. This will ensure Webb is in prime condition to begin the next major deployment step in its unfolding process.  
 
Specifically, the team is analyzing how the power subsystem is operating now that several of the major deployments have been completed. Simultaneously, the deployments team is working to make sure motors that are key to the tensioning process are at the optimal temperatures prior to beginning that operation.  
 
Using an approach to keep mission operations focused on as few activities as necessary at a time, mission managers have chosen to wait to resume sunshield deployment steps after better understanding the details of how Webb is functioning in its new environment.  
 
“Nothing we can learn from simulations on the ground is as good as analyzing the observatory when it’s up and running,” said Bill Ochs, Webb project manager, based at NASA’s Goddard Space Flight Center. “Now is the time to take the opportunity to learn everything we can about its baseline operations. Then we will take the next steps.”  
 
Webb’s deployment was designed so that the team could pause deployments if necessary. In this case, Ochs said, they are relying on that flexibility in order to properly address how the massive and complex observatory is responding to the environment of space.  
 
“We’ve spent 20 years on the ground with Webb, designing, developing, and testing,” said Mike Menzel, of NASA’s Goddard Space Flight Center, Webb’s lead systems engineer. “We’ve had a week to see how the observatory actually behaves in space. It’s not uncommon to learn certain characteristics of your spacecraft once you’re in flight. That’s what we’re doing right now. So far, the major deployments we’ve executed have gone about as smoothly as we could have hoped for. But we want to take our time and understand everything we can about the observatory before moving forward.”  
 
The timeline for deployments and NASA coverage will be updated as major deployments resume.

First Layer of Webb’s Sunshield Tightened
 
Today, at 3:48 pm EST, the Webb team finished tensioning the first layer of the observatory’s sunshield– that is, tightening it into its final, completely taut position. This is the first of five layers that will each be tightened in turn over the next two to three days, until the observatory’s sunshield is fully deployed. The process began around 10 am EST.
 
This layer is the largest of the five, and the one that will experience the brunt of the heat from the Sun. The tennis-court-sized sunshield helps keep the telescope cold enough to detect the infrared light it was built to observe.
 
The team has now begun tensioning the second layer.

Second and Third Layers of Sunshield Fully Tightened
 
The Webb team has completed tensioning for the first three layers of the observatory’s kite-shaped sunshield, 47 feet across and 70 feet long.
 
The first layer – pulled fully taut into its final configuration – was completed mid-afternoon.
 
The team began the second layer at 4:09 pm EST today, and the process took 74 minutes. The third layer began at 5:48 pm EST, and the process took 71 minutes. In all, the tensioning process from the first steps this morning until the third layer achieved tension took just over five and a half hours.
 
These three layers are the ones closest to the Sun. Tensioning of the final two layers is planned for tomorrow.
 
“The membrane tensioning phase of sunshield deployment is especially challenging because there are complex interactions between the structures, the tensioning mechanisms, the cables and the membranes,” said James Cooper, NASA’s Webb sunshield manager, based at Goddard Space Flight Center. “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.”
 
Once fully deployed, the sunshield will protect the telescope from the Sun’s radiation. It will reach a maximum of approximately 383K, approximately 230 degrees F, while keeping the instruments cold at a minimum of approximately 36K or around -394 degrees F.