James Webb Space Telescope

Today, Webb teams successfully deployed the observatory’s secondary mirror support structure. When light from the distant universe hits Webb’s iconic 18 gold primary mirrors, it will reflect off and hit the smaller, 2.4-foot (.74-meter) secondary mirror, which will direct the light into its instruments. The secondary mirror is supported by three lightweight deployable struts that are each almost 25 feet long and are designed to withstand the space environment. Specialized heating systems were used to warm up the joints and motors needed for seamless operation.

“Another banner day for JWST,” said Bill Ochs, Webb project manager at NASA’s Goddard Space Flight Center, as he congratulated the secondary mirror deployment team at the Mission Operations Center in Baltimore. “This is unbelievable…We’re about 600,000 miles from Earth, and we actually have a telescope.”

The deployment process began at approximately 9:52 a.m. EST, and the secondary mirror finished moving into its extended position at about 11:28 a.m. EST. The secondary mirror support structure was then latched at about 11:51 a.m. EST. At approximately 12:23 p.m. EST, engineers confirmed that the structure was fully secured and locked into place and the deployment was complete.

“The world’s most sophisticated tripod has deployed,” said Lee Feinberg, optical telescope element manager for Webb at Goddard. “That’s really the way one can think of it. Webb’s secondary mirror had to deploy in microgravity, and in extremely cold temperatures, and it ultimately had to work the first time without error. It also had to deploy, position, and lock itself into place to a tolerance of about one and a half millimeters, and then it has to stay extremely stable while the telescope points to different places in the sky – and that’s all for a secondary mirror support structure that is over 7 meters in length.”

Next Webb will deploy an important radiator system known as the aft deployable instrument radiator (ADIR), which helps shed heat away from its instruments and mirrors. Learn more about Webb’s deployment timeline online.

While the Webb team was tensioning the sunshield, other activities were also taking place among the instruments. One milestone: unlocking the Mid-Infrared Instrument (MIRI) Contamination Control Cover. We’ve asked Gillian Wright, European principal investigator for MIRI, to tell us about it.

“MIRI has a Contamination Control Cover, because the constraints of its extra-cold operating temperature mean that it is not possible to include other means of dealing with ice contamination, such as heaters for sensitive components. For launch it was safest to have this cover locked, and the timing for operating it is driven by the temperatures of the observatory.

“To unlock the cover, we first had to power on our Instrument Control Electronics and confirm that they were functioning correctly. Then the commands to the cover could be sent. After successfully completing the tests and unlocking the cover, the instrument control electronics were then powered off before the next steps on the sunshield tensioning activities. This key step for MIRI was monitored remotely by team members in Europe, ready to provide assistance if it were needed.

“The picture here shows tired and happy MIRI team members at the Mission Operations Center in Baltimore, after completing this first of the many MIRI commissioning steps. The MIRI Contamination Control Cover will be closed in the next few days to protect the optics from any possible contaminants as the observatory cools. It will then be reopened much later in the timeline, when MIRI has cooled to its operating temperature of just 7K and is ready to look out at the sky.”

—Gillian Wright, European principal investigator for the Mid-Infrared Instrument, UK Astronomy Technology Centre

At approximately 11:59 am EST, the fifth and final layer of Webb’s sunshield was fully tensioned, marking the completion of sunshield deployment. Read more about this key milestone in preparing Webb for science operations.

With three layers of Webb’s sunshield fully deployed, the team commenced tensioning – that is, pulling each layer fully taut – of the final two layers this morning.

We will have live coverage of the fifth layer tensioning at nasa.gov/live beginning at about 9:30 am EST.

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.

The Webb mission operations team began the first steps in the process of tensioning the first layer of Webb’s sunshield this morning around 10 a.m. EST.

It will take the team two to three days to tension the five-layer sunshield. The plan for today is to focus on the first layer, the largest and the one closest to the Sun.

This critical step in the observatory’s complex sequence of deployments resumed after Webb mission managers paused deployment operations on Saturday to allow for team rest, and then again on Sunday to make adjustments to Webb’s power subsystem and to alter the observatory’s attitude to lower the temperature of the motors that drive the tensioning process.

NASA’s Webb project manager Bill Ochs, Northrop Grumman’s vehicle engineering lead Amy Lo, and NASA’s Webb program director Greg Robinson provided more information about Webb’s first week in space and upcoming deployments in this teleconference held earlier today.

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.