The riskiest part of NASA's journey to deep space is just getting underway, as the James Webb Space Telescope has been in space for three days now. Soon, the telescope will begin an intricately choreographed mechanical dance as it slowly contorts its shape and unfurls, in order to reach its final form for observing the distant cosmos.
It is a type of reverse space origami that has never been done before and is necessary for the James Webb Space Telescope to fulfill its mission. The telescope was too large to be launched on a rocket. It was like the world's most expensive Swiss Army knife when it catapulted into space on top of a European Ariane 5 rocket.
We sometimes call him the transformer telescope.
Over the course of the next two weeks, the JWST will be configured so that it can peer into the deepest parts of the Universe. Amy lo, the alignments engineer at the telescope's primary contractor, tells The Verge that they sometimes call it the "Transformer Telescope". Engineers have tested hundreds of moving parts over and over again on the ground, as it has to be nothing short of flawless. There are many points where a failure of one small release mechanism or pulley could jeopardize the future of the entire mission. The mission controllers on the ground have a few techniques they can use if something gets stuck, but the JWST must do every deployment on its own to near perfect.
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The Ariane 5 rocket held the JWST on top.
Chris Gunn is the author of the image.
There are no operational rockets or spaceships that can safely bring astronauts to 1 million miles from Earth to give the telescope a tuneup. Even if humans could reach it, it wouldn't be good. If the telescope breaks in a fundamental way, it will be the end of the mission.
NASA says that there was never an easy path for the mission of this magnitude. Thomas Zurbuchen, the associate administrator for the science mission directorate at NASA, tells The Verge that it is not possible to make it simpler. This is what it is.
The designers of JWST knew that their creation would have to unfold in space. NASA administrator Dan Goldin challenged engineers to create a telescope with a primary mirror that was up to eight meters wide in 1996, when scientists first proposed making a telescope like this. The mirror that designers settled on was 21 feet across, but that decree determined the fate of the organization.
The largest rockets aren't wide enough to carry a mirror of that size. When you launch a rocket, you need to fit the spaceship inside the first part of the rocket's payload fairing. The fairing is important as it protects the payload from the atmosphere until it reaches space. Since the vehicle must fit inside, the vehicle's width is a major limiting factor. The problem is often referred to as the "tyranny of the fairing."
The primary mirror folded.
Chris Gunn is from NASA.
The Ariane 5 rocket has one of the widest payload fairings on the market, covering over 18 feet wide. It is too small to hold the mirror fully extended. The mirror was built in segments, with two flaps on either side that could be turned inward or outward. The design challenge was that the segments need to come together in a way that looks like a flat mirror in order to gather light. Unfurling a primary mirror has never been done before in space.
Unfurling a primary mirror has never been done before.
The mirror flaps will be put in around 12 to 13 days after launch. The deployment that the observatory must get through will take up to six days to complete. The sun shield is an intricate apparatus designed to block heat from the Sun and keep the telescope cool. The deployment process is designed to be flexible and could change, which means that almost everyone associated with this mission will be holding their breath for the next week.
Lee Feinberg, the optical telescope element manager for the NASA Goddard Space Flight Center, tells The Verge that the sun shield is the most complex. It has a lot of moving parts.
The sun shield is needed because of how the JWST is designed. The telescope will be looking at distant stars and galaxies in a type of light that is invisible to our eyes but emits heat. The temperature at which the JWST must operate to collect the infrared photons is -370 degrees Fahrenheit. The telescope might emit too much of its own light if it gets too warm.
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The sun shield extended and pulled taut.
Chris Gunn is the author of the image.
The sun shield provides some protection from the sun. Each layer of the shield is the size of a tennis court. Most of the heat from the Sun will come from the outermost layer, which is at a sizzling 230 degrees. Each layer will be cooler so that the instruments stay nice.
Extra special care and engineering was needed in order to extend the taut layers of the shield out into space and pull them without ripping them. Feinberg says there are systems that will spread the layers out. It is like a sail on a boat in terms of how you wind it up.
There are times when there are no backup options.
The entire process relies on hundreds of different moving parts, including up to 140 release mechanisms, 400 pulleys, 70 hinge assembly, and 90 cables. There are contingency plans in place if the deployment doesn't go as planned. If the first command doesn't cause a move, NASA has the option to send a new command. Engineers have made as many changes to the vehicle as they could. If the primary circuit doesn't fire properly, there are areas with multiple circuits that can perform the same task.
There are times when there are no backup options. There are more than 300 single point failures throughout the deployment process. They can't be built with redundant components, so they have to work as designed. There are single point failures that are funny. They are used a lot. This thing must happen. Throughout the deployment process, they are relied on a lot. The sun shield membranes need a total of 107 release devices to unfurl to their full shape. All of the devices are single point failures.
NASA has had many single point failures. According to Zurbuchen, the landing sequence for the Perseverance rover on Mars had 100 single point failures baked in. The entire landing was perfect. For the past two to three years, NASA and Northrop Grumman have tested the various deployment on the ground, intricately rehearsing them for the final show. Each component was tested individually on the ground before being added to the spaceship. The telescope was folded multiple times as a cohesive unit.
Do we have confidence in our ability to deploy? "Yes, we do," says Lo. We go through such rigorous testing from the ground level up.
Do we have confidence in our ability to deploy? Yes, we do.
The testing of the JWST took many years longer than planned, but it had to be rigorous because of its inability to be repaired. It is one of the biggest differences between the Hubble Space Telescope and the JWST. Hubble was designed to get tuneups by visiting astronauts, but the JWST doesn't have that capability. Sending humans to the telescope would cause too much heat. Zurbuchen says that even if you put a spacesuit around you, it is still warmer than the telescope environment.
NASA made a small design change in case they ever need to give the telescope a tuneup. There are crosses on the back of the JWST. They are meant to be targets to help guide a potential robotic visitor to the future. Over the last decade, various space companies have been working on "servicing satellites," designed to catch up with satellites already in space and grab hold of them, either to refuel their tanks or to tinker with aging components. It is possible that one day NASA will send a servicing satellite to the telescope to add more propellant to its tanks. If that happens, the targets will give a reference point for where the visiting spacecraft should attach to fill up the tank.
No one at NASA is thinking about that mission right now. Everyone associated with the organization is focused on the deployment. There is still a lot of work to be done as the observatory travels through deep space once the telescope is completely unfurled over the next two weeks. NASA will adjust the mirrors slightly to ensure they all align as they should. After 29 days after launch, the telescope will burn its thrusters and put it into its final position in deep space.
The work is just beginning. Mission personnel will calibrate all of the instruments to make sure they work. Science operations are scheduled to begin this summer.
The anxiety doesn't really end after two weeks if the deployment is planned. The instruments and the mirror phasing would have just begun, and a lot of us will breathe a sigh of relief. A different group of people, including the instrument builders, designers, engineers, and the scientists, would be holding their breath.
