While NASA's James Webb Space Telescope has faced countless obstacles and delays in its more than decade in the making, the observatory's most difficult days lie ahead in the coming months.
The James Webb Space Telescope, the successor to the Hubble Space Telescope, is set to launch on Dec. 18, 2021 aboard an Ariane 5 rocket from the European Space Agency's launch site near Kourou, French Guiana. Development for the observatory, said to be the most powerful space telescope ever built, began in 1996 with an initial launch planned for 2007. Now, 14 years later, the completed telescope has arrived at its launch site and is almost ready for liftoff.
About 28 minutes after liftoff, Webb will detach from its launch vehicle and begin "the most complex sequence of deployments ever attempted in a single space mission," according to NASA (opens in new tab). This deployment, which will see Webb unfold and unfurl its sun shield once in space, includes quite literally hundreds of "single points of failure," Mike Menzel, Webb lead mission systems engineer for NASA's Goddard Space Flight Center in Maryland, said Tuesday (Nov. 2) during a news briefing.
344 points of failure
"There are 344 single-point-of-failure items on average," Menzel said about the Webb mission, adding that "approximately 80% of those are associated with the deployment … It's hard to avoid when you have a release mechanism. It's hard to put full redundancy into that."
Webb has 144 release mechanisms "which all must work perfectly," Krystal Puga, Webb spacecraft systems engineer for Northrop Grumman, which built the spacecraft, said during the briefing.
"Like an origami object, proper folding and unfolding is necessary in order to achieve a specific shape," Alphonso Steward, Webb deployment systems lead for NASA Goddard, said during the briefing.
Menzel explained that the team decreased the number of release mechanisms as much as possible. "We found the sweet spot between getting the control that we want, with these large flexible membranes," without adding too many single points of failure, he said.
However, while the mission, and especially the deployment stage, have such a large number of single points of failure, Menzel emphasized the extensive work that the mission team has done to ensure success. "When we identify a single point failure, we give it very special treatment. We have what we call a critical item control plan, and we always throw in extra inspection points. And we've done extra offline testing on these devices," Menzel said.
He added that for every one of these items identified, NASA and Northrop Grumman have done extra inspections and tests to understand the different ways that it could fail, to be as prepared as possible. "We've given our single-point-failure items a lot of attention," he said.
Ensuring backup plans
Extra care has to be taken with these aspects of the mission because the team can't build in redundancy, but the mission overall also has many contingency plans, or plans for if things do not go as planned.
"We do have multiple contingency plans," Menzel told Space.com during the briefing. He added that some of the plans have been "pre-formulated" for the time-critical parts of deployment. "There's only one deployment really that time critical, and that's to get the solar array out," he said.
Steward added that contingency plans for Webb range from the super-simple to the very complex, with some plans being as straightforward as re-sending a command that did not go through. He said that there is "quite a bit of redundancy," in much of the Webb mission. "We have multiple ways of sending the same signal," he added.
And the Webb team has been making sure that their backup plans and built-in redundancies work as intended, just in case.
"Over the past two years or so, the team has been practicing these contingencies scenarios, where [an] anomaly is introduced, and the team will work to try to solve it and sort of rehearse plans," Steward said.
Over the course of the 24 years it's taken since development began, Webb is estimated to cost NASA $9.7 billion in total. The massive space observatory will succeed Hubble with a mirror six times the size of Hubble's and a sunshield about the size of a tennis court.
Webb will peer our into the farthest reachest of the universe, observing infrared light. Scientists hope to use the space telescope to see farther out into the universe, and therefore farther back in time, than ever before and learn about our universe's origins while uncovering new information about everything from planet formation to dark matter.