The James Webb Space Telescope's commissioning process is unfolding the universe.
However, the telescope will not be ready for scientific observations right away when it is launched.
In fact, the telescope won't make any observations for another six months after it's launched.
James Webb will spend the next month after separation from the Ariane 5 second stage deploying all of the instruments, mirrors, and structural systems that will be used for scientific observations.
The telescope will spend up to six months performing tests and calibrating systems for observations once it reaches its orbit at Earth-Sun Lagrange Point 2 (L2).
This entire deployment and testing process is known as commissioning, and it is an important part of a spacecraft's life that determines whether or not it will be able to function properly as expected.
Commissioning is a critical process for James Webb, and the entire telescope team will keep an eye on it.
NASASpaceflight spoke with Keith Parrish, James Webb's Observatory Manager and Commissioning Lead, to learn more about the mission's commissioning process and what the team can expect.
"Commissioning begins when the rocket leaves the ground," Parrish explained, "so once Ariane 5 takes off, that's when we say commissioning begins."
"Now that we're in orbit, we'll do a mid-course correction phase, where we'll use Webb's thrusters to correct any errors that Ariane 5 gave us. We tell the Ariane 5 team to send us in a certain direction at a certain velocity, and they'll get us really, really close to that target. We're talking [40,200 km/h], so we might have to put in a few meters per second of velocity [to get to the exact velocity
"We'll see how that first mid-course correction went on the first day, about 12 and a half hours after launch, and then about two days later, we'll do another small correction. The corrections will start getting smaller and really narrowing us down so that we're right on track to get to L2."
"We actually go into our deployments phase about three or four days after launch."
"We'll start with our sunshield deployment. We have very large pallets that are 20 to 30 feet tall that hold all of our membrane material [for the sunshield]. We have five small and very thin membranes that make up our sunshield, and we have to unfold all of that material and get it pulled into place. We start by lowering the front and back pallets down, which takes about a day. Then we start releasing all of our piping over the next two to three days
"Also, once we get that sunshield out, we start to see rapid cooling of our telescope and its instruments."
"So our telescope consists of a primary mirror, which is made up of eighteen individual mirror segments; for launch, we fold back six of the segments so Webb can fit inside the launch vehicle; and then we have a secondary mirror, which is actually what takes in all the light collected by the main mirror and puts it down into our cameras and instrument systems. The secondary mirror is mounted on a tripod that is broken up into diffraction gratings."
"We feel like we'll have the primary and secondary mirrors fully deployed somewhere in the 10 to 14-day range," Parrish said.
The Optical Telescope Element Manager for James Webb recently spoke with NASASpaceflight about the mirror's systems and complexity.
The mirror team from James Webb will then begin aligning each of the 18 individual mirror segments.
Each mirror has its own motor, which allows the team to "wiggle" all of them into place.
"After that, our optical folks will take about two weeks to start [aligning] those 18 mirrors around, and we'll also be turning on a lot of other electronics on the telescope, and we'll be getting the spacecraft more and more up and running as we bring more and more systems online."
"Then, around 30 days into the mission, we confirmed that everything moves and is deployed."
L2 orbital insertion is the next step in commissioning for James Webb and his team back on Earth.
"After that, we'll do a final mid-course correction burn to put us in our orbit at Lagrange Point 2, or L2," Parrish explained.
"The first 30 days are action-packed and very exciting; it doesn't stop; it's just one activity after another, but then it actually quiets down, and we'll be focused on our instruments and the telescope for the next two to three months."
However, in order to do so, the telescope must be properly cooled.
"It'll probably take three to four months to get everything down to the 30 to 50 Kelvin temperature ranges that [most instruments] require, but in the meantime, our optical team is continuing to align the telescope. They're continuing to do something called a wavefront sensing exercise, which is where they'll use one of the cameras to actually retrieve what we call the wavefront, which is really an optical metric for how aligned the telescope is. Then, based on that data, it'll
"During this time, we also do something called fine guiding, which is when we bring our Canadian instrument, the fine guidance sensor, FGS, online. It's basically a really, really high precision star tracker that allows the telescope to point to its astronomical targets, and it takes about two to four months."
The sunshield has now allowed James Webb to cool to the temperatures required for observations, but how does James Webb cool some of its instruments, and how do the instrument teams work to adapt their instruments to the temperatures?
"We have a mechanical cryocooler that cools the instruments down to the temperature we need, and we're getting very, very close to absolute zero on one of our instruments, the mid-infrared instrument (MIRI), which requires a mechanical cryocooler, so we're also bringing that cooler system online. That cooler system generates vibrations, so our optical team and our cooler team are working together to tune that cooler to make sure those vibrations don't interfere with the instruments."
James Webb is then handed over to the instrument teams.
"We have four instruments, and [those teams] will go through a series of calibration exercises with those instruments, which will include everything from measuring thermal stability to looking for dark areas to simply calibrating out all of the artifacts in the instruments that would interfere with science observations."
This delicate work will take two months, bringing the commissioning phase to a total of about six months.
Many instruments and spacecraft systems require redundancy due to the complex commissioning and deployment process.
So, how much redundancy is built into the deployment and commissioning process? What if a specific system fails to deploy? How long does the team have to fix the problem within the deployment/commissioning timeframe before serious problems arise?
"We paid a lot of attention to what we implemented in our systems," Parrish said. "But the one thing we really wanted to make sure of is that when it comes to our deployments, we are not on any clock. We can go as slow as we want to keep the entire Observatory safe."
There is, however, always an outlier.
"But remember those 170 release devices? In their natural state, mechanically, they want to be released, so we worked hard to make sure they didn't release prematurely. These release devices are also electrically redundant; we have two different systems that can release those devices."
That electrical redundancy also applies to the entire telescope.
"We have two computers on board that control all of our deployments, one primary and then a complete secondary backup computer that can handle all of our deployments, so all of our wiring is completely redundant as well."
"Take the sunshield, for example. You can't have two sunshields, so you can't have one sunshield that doesn't work and a full backup of it. That's obviously not feasible at all, so we built mechanical redundancy into the system."
"What we ended up finding was that our efforts to make something more reliable actually made it less reliable because we introduced more parts, so we've had to balance that. So now, when it comes to something like a motor, we have dual windings, which means there are two sets of windings in the motor that can be accessed by those two computers, as well as two sets of wiring, so we can always have electrical redundancy in our motors all the time."
On December 18, 2021, James Webb is scheduled to launch atop an Ariane 5 rocket from Kourou, French Guiana.
(Photo credit: NASA/Chris Gunn: Engineers inspect James Webb's secondary mirror after a deployment test.)