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Webb's Deployment

Webb's fully deployed operational configuration is far too large to fit into any available rocket so it was designed to fold into a compact launch configuration that fit inside the Ariane 5. In the two weeks after launch, the entire observatory underwent a highly choreographed transformation—unfurling, extending and expanding to a configuration that is very different to how it looks when stored inside the rocket for liftoff. 

Quick Facts
Video Overview
In Depth
Folding
Unfolding
29 Days on the Edge

Quick Facts

Quick Facts

Webb is the largest space telescope ever built. Its fully deployed operational configuration measures approximately 70ft long, 47 ft wide, 28 ft tall (21m x 14m x 8m ) far too big to fit into any available rocket.

Webb is the largest space telescope ever built. Its fully deployed operational configuration measures approximately 70ft long, 47 ft wide, 28 ft tall (21m x 14m x 8m ) far too big to fit into any available rocket.

The Ariane 5 launch vehicle's rocket fairing has a diameter of approximately 18 ft (5.4 m) x 43ft (13m) tall. Webb was designed to fold compactly to fit into the fairing.

The Ariane 5 launch vehicle's rocket fairing has a diameter of approximately 18 ft (5.4 m) x 43ft (13m) tall. Webb was designed to fold compactly to fit into the fairing.

Webb began deployment shortly after launch, first automatically deploying the solar array for power and the high gain antenna. The remaining deployments were carefully choreographed from ground control by Webb engineers and progress was monitored via telemetry data.

Webb began deployment shortly after launch, first automatically deploying the solar array for power and the high gain antenna. The remaining deployments were carefully choreographed from ground control by Webb engineers and progress was monitored via telemetry data.

The complex high stakes deployment process included over 50 major deployments with 178 release mechanisms that all had to work properly.

The complex high stakes deployment process included over 50 major deployments with 178 release mechanisms that all had to work properly.

There were over 300 possible single points of failure. Since Webb operates at approximately 1 million miles from Earth, there was no possibility for a repair mission.

There were over 300 possible single points of failure. Since Webb operates at approximately 1 million miles from Earth, there was no possibility for a repair mission.

Webb's deployment was completed with remarkable smoothness. Webb continued its cooldown phase meeting thresholds for mirror alignment and later for instruments to come online and be calibrated. The final results exceeded requirements and expectations.

Webb's deployment was completed with remarkable smoothness. Webb continued its cooldown phase meeting thresholds for mirror alignment and later for instruments to come online and be calibrated. The final results exceeded requirements and expectations.

Video Overview

Webb Folded

Webb is so large that it could not fit into any available rocket fairing so it was designed to fold into a compact launch configuration that fit inside the Arianne 5 rocket. This animation shows highlights the size differences between Webb's fully deployed configuration and its launch configuration folded to fit in the rocket.

Webb Unfolded

After launch while on its journey to L2, engineers on the ground remotely orchestrated and monitored a complex sequence of deployments in the hours and days immediately after the launch. This animation shows the nominal sequence for these deployments.

A sequence of major deployment states of Webb shown horizontally on black background in a row
A sequence of selected major deployment steps of Webb.
Steve Sabia / GSFC CI Lab

In Depth

Webb's design, development and intensive testing were keys to the success of the complex deployment process. There were over 50 major deployment steps, with 178 release mechanisms that had to perform perfectly or any one of over 300 single points of failure could have diminished or crippled the mission.

Not only that, but Webb and its subsystems were sourced from all over the world. The assembled optical telescope element alone moved multiple times across the USA before final integration and test in California with the remainder of the spacecraft. Webb's final move involved shipping it by boat from California, through the Panama Canal and to the launch pad in French Guiana in South America. Each of these moves is risky. In the end, Webb deployed and came online exceeding requirements and expectations.

Below you will find sections covering various aspects of design and deployment in deeper detail.

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Folding For Launch

Webb's design was not only driven by the science requirements for the mission, but also by the need to be able to fold it tightly for launch and succesfully deploy it in space while in flight to its final destination orbitting L2. These images highlight some of the major design features and preparation steps for launch.

The James Webb Space Telescope 3d rendering from view slightly below the sunshield revealing most of the major components and subsystems. Labeled image showing major Webb observatory subsystems
The James Webb Space Telescope's fully deployed operational configuration was designed to be folded into the Ariane 5 launch vehicle's rocket fairing.
NASA/ GSFC CIL

The James Webb Space Telescope mirrors upright on a white stand in the NASA Goddard cleanroom. The 3 mirrors on the right “wing” are folding back like a leaf on a drop-leaf table. The telescope has 18 golden hexagonal segments. The secondary mirror support structure, made of three thin black lines, is folded and the secondary mirror sits atop this folded tripod. There are 5 people in white cleanroom suits supervising the folding maneuver. One of them is on a red lift at the back right. There is a wall of HEPA filters behind the telescope.
Webb's folding mirrors include the primary mirror wings and the secondary mirror and booms. NASA’s James Webb Space Telescope is shown with one of its two “wings” folded. Each wing holds three of its primary mirror segments. During this operation in the clean room at NASA Goddard, the telescope was also rotated in preparation for the folding back of the other wing. When Webb launched, both wings were stowed in this position, which enabled the mirror to fit into the launch vehicle. This image was captured July 17, 2016.
NASA/Chris Gunn
NASA’s Webb Sunshield Successfully Unfolds and Tensions in Final Tests
Webb is now in its final series of deployment and checkout tests before the observatory is packed for shipment to French Guiana for launch aboard an @ArianeGroup Ariane V rocket. These tests will verify that Webb will deploy perfectly in space after its launch.
NASA/Chris Gunn
Webb in the Northrup Grumman clean room for final integration and test before launch. Technicials are preparing the sunshield and sunshield covers into their folded launch configuration
Webb's 5 layer folding sunshield, each layer less than the thickness of a human hair, needed to be carefully folded for the complex, "in flight", deployment in space. The image is from April 2020. Webb in the Northrup Grumman clean room for final integration and test before launch. Technicians preparing the sunshield and sunshield covers into their folded launch configuration.
Northrop Grumman
This archival image is from May 2021 when Webb was at the Northrop Grumman facility. During this approximate time period (late spring to early summer), the telescope was having its sunshield packed up and prepped for launch, and the final test fold of the mirror wings was also taking place.
This archival image is from May 2021 when Webb was at the Northrop Grumman facility. During this approximate time period (late spring to early summer), the telescope was having its sunshield packed up and prepped for launch, and the final test fold of the mirror wings was also taking place.
NASA/Chris Gunn
Webb is encapsulated in its rocket fairing
On Friday 17 December 2021, the Ariane 5 rocket fairing was closed around the James Webb Space Telescope. This protective fairing, or ‘nose cone’, will shield the telescope during liftoff and its journey through the atmosphere on 24 December.
ESA/CNES/Arianespace
James Webb Space Telescope Launch
Arianespace's Ariane 5 rocket launches with NASA’s James Webb Space Telescope onboard, Saturday, Dec. 25, 2021, from the ELA-3 Launch Zone of Europe’s Spaceport at the Guiana Space Centre in Kourou, French Guiana.
NASA/Bill Ingalls
This image shows the James Webb Space Telescope atop its launch vehicle
Webb in it's folded launch configuration, being prepared to be inserted into the rocket fairing.
NASA/Chris Gunn
Webb Launch Vehicle Components
Webb Launch Vehicle Components
Arianespace
Simulated view of the James Webb Space Telescope (JWST) in it's folded and stowed launch configuration inside the nose cone of an Ariane 5 rocket.
Simulated view of the James Webb Space Telescope (JWST) in it’s folded and stowed launch configuration inside the nose cone of an Ariane 5 rocket.
Arianespace
Montage of Webb (JWST) in it's folded and stowed launch configuration inside the nose cone of an Ariane 5 rocket.
Montage of the James Webb Space Telescope (JWST) in it's folded and stowed launch configuration inside the nose cone of an Ariane 5 rocket.
Illustration credit Courtesy of ArianeSpace.com. Photo credit: ESA-CNES-Arianespace/Optique Vidéo du CSG-OV.
NASA, Partners Roll Out Webb to Launch Pad
NASA’s James Webb Space Telescope has begun its stately rollout to the Arianespace ELA-3 launch complex at Europe’s Spaceport located near Kourou, French Guiana. Arianespace and NASA will closely monitor the vitals of Webb and the Ariane 5 rocket during the nearly two-hour process. Webb is scheduled for liftoff at 7:20 am EST Saturday, Dec. 25.
NASA/Chris Gunn
Prelaunch of Ariane 5 with James Webb Space Telescope
Arianespace's Ariane 5 rocket with NASA’s James Webb Space Telescope onboard, is seen in the final assembly building ahead of the planned roll to the launch pad, Thursday, Dec. 23, 2021, at Europe’s Spaceport, the Guiana Space Center in Kourou, French Guiana.
NASA/Chris Gunn
Ariane 5 with James Webb Space Telescope Prelaunch
Arianespace's Ariane 5 rocket with NASA’s James Webb Space Telescope onboard, is seen at the launch pad, Thursday, Dec. 23, 2021, at Europe’s Spaceport, the Guiana Space Center in Kourou, French Guiana.
NASA/Chris Gunn
Webb’s Ariane 5 rocket launches from Europe’s Spaceport in Kourou, French Guiana. A glowing, white-yellow stream of gas and fire is streaming from the rocket towards the ground below. The ground is covered with puffy clouds of pink-orange gas. In the background, lit up by the launch, is a building that is emblazoned with dark blue European Space Agency (ESA) and Ariane logos. The sky is a dark blue-gray and largely cloudy.
“Liftoff – from a tropical rainforest to the edge of time itself, James Webb begins a voyage back to the birth of the universe.” Arianespace's Ariane 5 rocket launched with NASA’s James Webb Space Telescope aboard, Dec. 25, 2021, from the ELA-3 Launch Zone of Europe’s Spaceport at the Guiana Space Centre in Kourou, French Guiana.
NASA/Chris Gunn
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Unfolding Webb

Webb's First 6 Months

The Ariane 5 launch vehicle provided thrust for roughly 26 minutes after liftoff from French Guiana. Moments after the upper (second) stage engine cut-off, Webb separated from the upper stage and began flying on its own in its fully stowed state. Deployments began minutes after separation.

Webb in its folded launch configuration separates from the Ariane 5 upper stage.
Webb in its folded launch configuration separates from the Ariane 5 upper stage. Deployments started minutes after separation.
Steve Sabia / GSFC CI Lab
Last Glimpse of the James Webb Space Telescope before it goes deep into space.
A camera on board the upper stage of the Ariane 5 rocket caught this last glimpse of Webb just after it separated and began its deployment and journey to L2.
Arianespace, ESA, NASA, CSA, CNES
  • First day: The solar panel automatically deployed to supply Webb with power and the high gain antenna deployed for high bandwidth communications. The Ariane launch sent Webb on a direct route to L2, without first orbiting Earth. During the first day, a first and most important trajectory correction maneuver was executed using small rocket engines aboard Webb itself. Ariane's launch was so accurate that very little correction was needed, saving fuel for operations and extending Webb's operational lifetime.
  • In the first week: Sunshield deployment:  Shortly after a second trajectory correction maneuver was executed, the sequence of major deployments began with the fore and aft sunshield pallets. The next step was separation of the spacecraft bus and telescope by extending the telescoping tower between them. The tower extended about 2 meters, which was necessary at this point in the sequence so that the rest of the sunshield deployment could proceed. Next, the sunshield membranes were unpinned and the telescoping sunshield midbooms were extended – first the port side and then the starboard side – pulling the membranes out with them. The last sunshield deployment step was the tensioning of the membranes. In the meantime, other things like radiators were released and deployed.
  • Second Week:  Mirror/Telescope Deployment: During the second week after launch, we finished deploying the telescope structures by unfolding and latching the secondary mirror tripod and rotating and latching the two primary mirror wings. This brought Webb into its fully deployed operational configuration.
A sequence of deployment step images from the launch pad to fully deployed
A sequence of major deployment steps from launch configuration to a fully deployed operational configuration Webb Space Telescope.
Steve Sabia, GSFC CI Lab
  • 1st Month: Cooldown, instrument turn-on, and insertion into orbit around L2. The telescope and scientific instruments started to cool rapidly in the shade of the sunshield, but it took several weeks for them to cool all the way down and reach stable temperatures. This cooldown was carefully controlled with strategically-placed electric heater strips so that everything shrinks carefully and so that water trapped inside parts of the observatory can escape as gas to the vacuum of space and not freeze as ice onto mirrors or detectors, which would degrade scientific performance. We unlocked all the primary mirror segments and the secondary mirror and verified that we can move them. Near the end of the first month, we executed the last mid-course maneuver to insert into the optimum orbit around L2. During this time we also powered-up the scientific instrument systems. The remaining five months of commissioning were all about aligning the optics and calibrating the scientific instruments.
This graph shows a sample of temperature monitors on the hot (a, b) and cold (c,d) sides of Webb during its cooldown phase. Note the major changes in the area marked as days 3-10 when the sunshield was deployed.
Steve Sabia / NASA
  • In the second, third and fourth months: Initial optics checkouts, and telescope alignment. Using the Fine Guidance Sensor, we pointed Webb at a single bright star and demonstrated that the observatory could acquire and lock onto targets, and we took data mainly with NIRCam. But because the primary mirror segments had yet to be aligned to work as a single mirror, there were distorted images of the same single target star. We then embarked on the long process of aligning all the telescope optics, beginning with identifying which primary mirror segment went with which image by moving each segment one at a time and ended a few months later with all the segments aligned as one and the secondary mirror aligned optimally. Cooldown effectively ended and the cryocooler started running at its lowest temperature and MIRI started taking good data too.
  • In the fifth and sixth months: Calibration and completion of commissioning. We meticulously calibrated all of the scientific instruments’ many modes of operation while observing representative targets, and we demonstrated the ability to track “moving” targets, which were nearby objects like asteroids, comets, moons, and planets in our own solar system. We made “Early Release Observations,” to be revealed right after commissioning was over, that showcased the capabilities of the observatory.
  • After six months: “Science operations!” Webb began its science mission and started to conduct routine science operations.