Webb Begins Its Months-Long Mirror Alignment

Webb has begun the detailed process of fine-tuning its individual optics into one huge, precise telescope.

Engineers first commanded actuators – 126 devices that will move and shape the primary mirror segments, and six devices that will position the secondary mirror – to verify that all are working as expected after launch. The team also commanded actuators that guide Webb’s fine steering mirror to make minor movements, confirming they are working as expected. The fine steering mirror is critical to the process of image stabilization.

Ground teams have now begun instructing the primary mirror segments and secondary mirror to move from their stowed-for-launch configuration, off of snubbers that kept them snug and safe from rattling from vibration. These movements will take at least ten days, after which engineers can begin the three-month process of aligning the segments to perform as a single mirror.

Following the Next Steps in Webb’s Journey

After two weeks of complex structural deployments, Webb has passed a major milestone and is now fully unfolded in space. For insight on what to expect in the months ahead and how to follow along, we hear from Alexandra Lockwood, project scientist for Webb science communications at the Space Telescope Science Institute:

“Words can’t describe the pride and excitement the Webb team is feeling right now. From engineers to scientists to IT staff to graphic designers to administrative personnel (and more!), we are all overjoyed with the incredible successes of the observatory to date. While we still have a long way to go before getting the science, the engineering feats that have been accomplished, on Earth and now in space, are awe-inspiring. They are a testament to the hard work and expertise of the international Webb team.

“Now that the action-packed deployment sequence is over, we are moving into a much slower, yet deliberate, phase of the commissioning process. In the next two weeks, we will move each of the 18 primary mirror segments, and the secondary mirror, out of their launch positions. Then five months of commissioning will include 1) further cooling of the entire observatory, and of the Mid-Infrared Instrument in particular, 2) checking and then aligning the secondary and 18 mirror segments into a single coherent optical system, first with the NIRCam instrument and then with all instruments individually and in parallel, and 3) calibrating of each of the four instruments and their many scientific modes. The novelty and variety of science that this observatory can produce requires thousands of things to be checked ahead of time. But rest assured that this summer will sizzle with the hot (nay cold?) observations we will soon be sharing!

“The team is committed to keeping you informed – even through the often slow and meticulous parts of this commissioning process. This blog will be updated weekly, and sometimes more often. Please check back to hear more status updates, in-depth explanations of Webb’s science and technology, and even some fun team anecdotes!

“We’re excited to be on this journey to #UnfoldTheUniverse with you.”

—Alexandra Lockwood, project scientist for Webb science communications, Space Telescope Science Institute

Primary Mirror Wings Deployed, All Major Deployments Complete

Today, at 1:17 p.m. EST, NASA’s James Webb Space Telescope completed all of its large-scale deployments with the extension and latching of its starboard primary mirror wing. Now that the telescope is structurally fully deployed – with the secondary mirror tripod and both primary mirror wings in place – the three-month process of aligning all of Webb’s telescope optics into a precise system can now commence. Learn more.

Starboard Primary Mirror Wing Deployment Underway

The Webb mission operations team has given the ‘go-ahead’ to move forward with the extension of its starboard primary mirror panel. This is the last of the major deployments on the observatory, and its completion will set the stage for the remaining five and a half months of commissioning, which consist of settling into stable operating temperature, aligning the mirrors, and calibrating the science instruments.

Live coverage of the deployment, from the Webb Mission Operations Center at the Space Telescope Science Institute in Baltimore, will stream on nasa.gov/live starting no earlier than 9 a.m. EST.

First of Two Primary Mirror Wings Unfolds

Webb’s iconic primary mirror is taking its final shape. Today, the first of two primary mirror wings, or side panels, was deployed and latched successfully. Each side panel holds three primary mirror segments that were engineered to fold back to reduce Webb’s overall profile for flight.

The process of deploying the port side mirror wing began at approximately 8:36 a.m. EST. At approximately 2:11 p.m. EST, engineers confirmed that the panel was fully secured and locked into place, and the deployment was complete.

Now that the port side wing panel is locked in place, ground teams will prepare to deploy and latch the starboard (right side) panel tomorrow. Upon completion, Webb will have concluded its major deployment sequence.

Learn more about Webb’s deployment timeline online.

Primary Mirror Deployment Has Begun

Engineers have begun the final stage of Webb’s major structural deployments: the unfolding of its two primary mirror wings. These side panels, which were folded back for launch, each hold three of the observatory’s 18 hexagonal, gold-coated mirror segments.

The team is beginning today with the mirror wing on the port (left) side of the observatory. Engineers must first release mechanisms that held the wing in place for launch, in order to allow the wing to deploy. The panel then rotates into position, a motor-driven process that takes about five minutes. Once the wing is extended, engineers begin a meticulous, two-hour process to securely latch it into place.

The deployment of the second primary mirror wing, planned for tomorrow, will follow the same process.

Why Doesn’t Webb Have Deployment Cameras?

As NASA’s James Webb Space Telescope makes its way out to its intended orbit, ground teams monitor its vitals using a comprehensive set of sensors located throughout the entire spacecraft. Mechanical, thermal, and electrical sensors provide a wide array of critical information on the current state and performance of Webb while it is in space.

A system of surveillance cameras to watch deployments was considered for inclusion in Webb’s toolkit of diagnostics and was studied in-depth during Webb’s design phase, but ultimately this was rejected.

“Adding cameras to watch an unprecedently complicated deployment of such a precious spacecraft as Webb sounds like a no-brainer, but in Webb’s case, there’s much more to it than meets the eye,” said Paul Geithner, deputy project manager – technical for the Webb telescope at NASA’s Goddard Space Flight Center. “It’s not as straightforward as adding a doorbell cam or even a rocket cam.”

First of all, Webb is big, undergoes many configuration changes during deployment, and has many specific locations of import to deployment. Monitoring Webb’s deployments with cameras would require either multiple narrow-field cameras, adding significant complexity, or a few wide-field cameras that would yield little in the way of helpful detailed information. Wiring harnesses for cameras would have to cross moving interfaces around the observatory and add more risk of vibrations and heat leaking through, presenting a particular challenge for cameras located on the cold side of Webb.

Then there’s the issue of lighting. Webb is very shiny, so visible cameras on the Sun-facing side would be subject to extreme glare and contrast issues, while ones on the cold, shaded side would need added lighting. Although infrared or thermal-imaging cameras on the cold side could obviate the need for illumination, they would still present the same harnessing disadvantages. Furthermore, cameras on the cold side would have to work at very cold cryogenic temperatures. This would either require ‘ordinary’ cameras to be encapsulated or insulated so they would work in extreme cold, or development of special-purpose cryogenic-compatible cameras just for deployment surveillance.

Notwithstanding these challenges, engineers mocked up and tested some camera schemes on full-scale mockups of Webb hardware. However, they found that deployment surveillance cameras would not add significant information of value for engineering teams commanding the spacecraft from the ground.

“Webb’s built-in sense of ‘touch’ (for example, switches and various mechanical, electrical, and temperature sensors) provides much more useful information than mere surveillance cameras can,” said Geithner. “We instrumented Webb like we do many other one-of-a-kind spacecraft, to provide all the specific information necessary to inform engineers on Earth about the observatory’s health and status during all activities.” Engineers can also correlate years of data from ground testing with telemetry data from flight sensors to insightfully interpret and understand flight sensor data.


By Thaddeus Cesari, Webb science writer, NASA’s Goddard Space Flight Center, Greenbelt, Md.

Webb’s Specialized Heat Radiator Deployed Successfully

At about 8:48 a.m. EST, a specialized radiator assembly necessary for Webb’s science instruments to reach their required low and stable operating temperatures deployed successfully. The Aft Deployable Instrument Radiator, or ADIR, is a large, rectangular, 4 by 8-foot panel, consisting of high-purity aluminum subpanels covered in painted honeycomb cells to create an ultra-black surface. The ADIR, which swings away from the backside of the telescope like a trap door on hinges, is connected to the instruments via flexible straps made of high-purity aluminum foil. The radiator draws heat out of the instruments and dumps it overboard to the extreme cold background of deep space.

The deployment of the ADIR – a process that released a lock to allow the panel to spring into position – took about 15 minutes.

Webb’s final series of major deployments is planned to start tomorrow, Jan. 7, with the rotation into position of the first of two primary mirror wings. The second primary mirror wing – Webb’s final major spacecraft deployment – is planned for Saturday, Jan. 8.

Secondary Mirror Deployment Confirmed

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.

MIRI Instrument Marks a First Milestone in Space

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 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