5 critical moments will determine the success or failure of NASA’s James Webb Space Telescope

On December 22, 2021, NASA’s James Webb Space Telescope will finally launch.

James Webb will have seven times the light-gathering power of Hubble, but will be able to see much farther into the infrared portion of the spectrum, revealing those galaxies existing even earlier than what Hubble could ever see. Galaxy populations seen prior to the epoch of reionization should abundantly be discovered, including at low masses and low luminosities, by James Webb beginning in 2022. (Credit: NASA/JWST Science Team; composite by E. Siegel)

Success means humanity’s most powerful space observatory ever.

The same object, the Pillars of Creation in the Eagle Nebula, can have vastly different details revealed dependent on the wavelength of light used. Here, the visible light (L) and near-infrared (R) views are shown, both taken with the Hubble Space Telescope. Capable of extending much farther in the infrared than Hubble, James Webb will view details in this (and other) objects that have never been glimpsed before. (Credit: NASA, ESA/Hubble and the Hubble Heritage Team)

Failure means the most expensive “space junk” in history.

NASA’s James Webb Space Telescope, as shown during a “lights out” inspection after its final vibration and acoustic test, performed in October of 2020. Having passed that final test without any red or yellow flags, Webb is ready for launch, but must endure and survive a number of critical milestones before it can even begin taking science data. (Credit: NASA/Chris Gunn)

These five critical events will determine its fate.

A rough launch-and-deployment diagram of the order-of-operations of the James Webb Space Telescope. Depending on what happens during the mission, these timetables may vary significantly, but this is the expected order of the most critical stages of initial deployment. (Credit: NASA/Clampin/GSFC)

1.) The Ariane 5 launch.

This 2017 launch of an Ariane 5 rocket mirrors the launch vehicle of NASA’s James Webb Space Telescope. The Ariane 5 had a string of more than 80 consecutive launch successes before a partial failure in January of 2018. This launch, the 82nd successful one in a row before that failure, hopefully offers a preview of James Webb’s launch. (Credit: ESA-CNES-ARIANESPACE/Optique Video du CSG – OV)

After 82 consecutive successes, a 2018 launch went catastrophically off course.

The Ariane 5 rocket has been one of humanity’s most reliable launch vehicles, with a string of 82 successful launches from 2003 to 2018. That string was broken in early 2018, and despite the successes since, no one is taking Webb’s successful launch for granted. (Credit: NASA/James Webb Space Telescope team)

Webb subsequently burns fuel for course corrections: the same fuel needed for telescope operations.

An artist’s conception (2015) of what the James Webb Space Telescope will look like when complete and successfully deployed. Note the five-layer sunshield protecting the telescope from the heat of the Sun, and the fully-deployed primary (segmented) and secondary (held by the trusses) mirrors. The same fuel used to maneuver Webb in space will be required to point it at its targets and keep it in orbit around L2. (Credit: Northrop Grumman)

Without an L2 Lagrange point arrival, Webb will be utterly useless.

Assuming a successful launch and deployment, Webb will enter orbit around the L2 Lagrange point, where it will cool, turn its instruments on, calibrate everything, and then begin science operations. Everything rests on its successfully getting there. (Credit: ESA)

2.) Separation and solar array deployment.

30 minutes after liftoff, the final separation of the James Webb Space Telescope from the last stage of the launch vehicle will occur. Just ~3 minutes later, the solar array will plan on deploying. If this occurs successfully, the spacecraft will gather the power necessary for all future operations. If it fails, the mission will end prematurely: in failure. (Credit: ESA/D. Ducros)

Occurring ~30 minutes after launch, deploying the solar array is mandatory.

30 minutes after launch, the spacecraft will separate from the final stage of the launch vehicle. Just 3 minutes later, the solar array must deploy. If the deployment fails, Webb’s battery will last mere hours before the telescope runs out of power entirely. (Credit: NASA/James Webb Space Telescope team.)

An unsuccessful deployment will cause power failure after mere hours, ending Webb’s life prematurely.

All five layers of the sunshield must be properly deployed and tensioned along their supports. Every clamp must release; every layer must not snag or catch or rip; everything must work. If not, the telescope will not cool properly, and it will be useless for infrared observations: its primary purpose. Shown here is the sunshield prototype, a one-third scale component. (Credit: Alex Evers/Northrop Grumman)

3.) Full sunshield deployment.

In order to deploy the sunshield, aft and forward sunshield pallets, as well as other support and protective structures, must first come out and deploy properly. Only then, once the proper setup is in place, can the sunshield come out and be tensioned. (Credit: Northrop Grumman)

After deploying support structures and the tower assembly, a cumulative 178 sunshield releases must fire.

The process of tensioning and unfurling the 5-layer sunshield aboard NASA’s James Webb Space Telescope is shown here. If the support structures fail, if the sunshield catches or snags, or if every one of the 178 “releases” that must occur doesn’t succeed, the mission could be a total loss. (Credit: NASA/James Webb Space Telescope team.)

If it fails, or if tensioning catches or snags, the telescope won’t cool: a catastrophic loss.

During a 2018 environmental test of the spacecraft element, some screws and washers came off of the bus and sunshield: a flaw that required correction. As of the last and final round of vibration and acoustic testing, this problem appears to have been successfully corrected, while no other comparable ones have arisen. This is essential, as if either the sunshield or the mirrors fail to properly deploy, the mission could be a total loss. (Credit: NASA/Chris Gunn)

4.) Mirror deployments.

The 18 segmented mirrors must unfold, deploy, and form a single surface that’s calibrated to a positional precision of ~20 nanometers, while the secondary mirror must then focus that light precisely onto the instruments. Any failure here would be disastrous for the telescope. (Credit: NASA/James Webb Space Telescope team)

The primary mirror must deploy, making a single, smooth surface to ~20 nanometer precision.

The secondary mirror’s deployment sequence is shown in this time lapse image. It must be precisely located just under 24 feet, or a little over 7 meters, from the primary mirror. The support structures must not fail. (Credit: NASA/James Webb Space Telescope team)

The secondary mirror focuses the gathered light; any misalignment is ruinous.

When all the optics are properly deployed, James Webb should be able to view any object beyond Earth’s orbit in the cosmos to unprecedented precision, with its primary and secondary mirrors focusing the light onto the instruments, where data can be taken, reduced, and sent back to Earth. (Credit: NASA/James Webb Space Telescope team)

5.) L2 orbital insertion.

Every planet orbiting a star has five location around it, Lagrange points, that co-orbit. An object precisely located at L1, L2, L3, L4, or L5 will continue to orbit the Sun with precisely the same period as Earth does, meaning that the Earth-spacecraft distance will be constant. L1, L2, and L3 are unstable points of equilibrium, requiring periodic course corrections to maintain a spacecraft’s position there, while L4 and L5 are stable. Webb is headed to L2, and must always face away from the Sun for cooling purposes. (Credit: NASA)

29 days post-launch, Webb’s thrusters fire, entering orbit around L2: its ultimate destination.

If these five mission-critical steps succeed, calibration and science operations commence.

A portion of the Hubble eXtreme Deep Field that’s been imaged for 23 total days, as contrasted with the simulated view expected by James Webb in the infrared. With the COSMOS-Webb field expected to come in at 0.6 square degrees, it should reveal approximately 500,000 galaxies in the near-infrared, uncovering details that no observatory to date has been able to see. (Credit: NASA/ESA and Hubble/HUDF team; JADES collaboration for the NIRCam simulation)

Only fuel limits Webb’s operational lifetime.

Although it was not designed for servicing, it remains technically possible for a robotic spacecraft to meet up with and dock with James Webb to refuel it. If this technology can be developed and launched before Webb runs out of fuel, it could extend Webb’s life by ~15 years or so. (Credit: NASA)

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