Share the news of December 29 with friends and circle of friends with wechat scanning QR code < / P > < p >, NASA's James Webber Space Telescope (JWST) has been flying in space for three days, but the most risky part of its space journey has just begun. Soon, the telescope will begin a carefully choreographed mechanical dance, slowly changing its shape and unfolding into its final form, so as to observe the distant universe. < / P > < p > figure 1: the Weber Space Telescope has been launched for three days and is about to change into its final form

This is a reverse space origami that has never been done before, but it is necessary for the Weber telescope to complete its expected mission. The size of the Weber telescope is too large to carry any controllable rocket launch when it is fully deployed. Therefore, the telescope was folded like a Swiss Army knife when it went into space on the Ariane 5 rocket at Christmas < p > over the next two weeks, the Weber telescope will reshape until it is fully configured to peep into the deepest part of the universe. Amy lo, an engineer of Northrop Grumman, the main contractor of Weber telescope, explained: "we sometimes call Weber 'transformer telescope'." < p > deploying the final form is a daunting process. Hundreds of moving parts need to be redeployed. Engineers have repeatedly tested it on the ground because it must be flawless. But in this process, even a small release mechanism or pulley failure may endanger the future of the whole Weber telescope. Although the ground mission control personnel have mastered a lot of troubleshooting techniques, if something gets stuck, they can intervene immediately, but ultimately the telescope must complete each deployment by itself to get close to perfection < p > Figure 2: Weber space telescope was completely folded on top of Ariana 5 rocket before launch < / P > < p > Weber space telescope is going to its final destination about 1.6 million kilometers away from the earth. At present, no rocket or spacecraft can safely take astronauts to such a far place to adjust the telescope. Therefore, if the Weber telescope has an irreparable failure, it will mean the end of the mission, which cost a total of $9.7 billion < p > for tasks of this scale, it has always been very complex. The designers of Weber telescope knew from the beginning that their design must be able to be carried out in space. As early as 1996, when scientists first proposed to build such a telescope, then NASA Director Dan Goldin challenged engineers to build a telescope with a main mirror diameter of 8 meters. Finally, the designers chose a mirror with a diameter of 6.5 meters < p > this is because the largest rocket currently flying is not big enough to take off with such a big mirror. Whenever anything is launched into space, the payload must be installed in the fairing of the rocket. This design is crucial because it covers the top of the rocket during launch and can protect the payload from the atmosphere until it goes into space. However, the diameter of the fairing is a major limitation in spacecraft design, because the aircraft must be able to be installed in it < p > Figure 3: the main mirror of Weber space telescope is folded and will not be fully deployed until it goes into space < / P > < p > Ariana 5 rocket has one of the largest payload fairings on the market, with a diameter of 5.4 meters. But it is still too small to accommodate the main mirror of the Weber telescope. Therefore, the mission designer of the Weber telescope divided the mirror into several parts from the beginning, with two flaps on each side that can rotate inward and outward. This is a major design challenge because these parts need to be perfectly aggregated, like a complete mirror, in order to collect light from the distant universe. "We have never tried to deploy the primary mirror in space orbit," Amy Rowe said < p > the Weber telescope will deploy its primary mirror about 12 to 13 days after launch. But before that, it must complete a more complex task, which takes up to six days. This is the deployment of the telescope sunscreen. It is a complex device designed to block the heat from the sun and help cool the telescope in space. Although the deployment process is designed to be very flexible and can change as the situation changes, the first step of sunscreen deployment will begin immediately, which means that almost everyone related to this task will wait with bated breath next week < p > Lee Feinberg, optical telescope element manager of NASA's Goddard Space Flight Center, said: "in all our deployments, the sunscreen itself is the most complex because it has the most moving parts." < p > due to the design of Weber telescope, the sunscreen is a necessary function. The telescope will use infrared to observe distant stars and galaxies. Infrared is a kind of light invisible to the naked eye, but any object containing heat will emit this light. In order to collect infrared photons, the Weber telescope must work at ultra-low temperatures as low as minus 188 degrees Celsius. If it gets too hot, the telescope itself may emit too much infrared, which may interfere with its observation of the universe < p > Figure 4: unfolding and tightening state of the sun shield of Weber Space Telescope < / P > < p > this sun shield provides good protection for Weber space telescope. It is composed of five layers of ultra-thin shiny material called Kapton, each layer is the size of a tennis court. The outermost layer will always face the sun and absorb most of the heat, with an operating temperature of up to 100 degrees Celsius. But then each layer will become colder and colder, so that the instruments on the telescope can maintain a good low temperature < p > the heat reflective film of the sunscreen is very fragile and requires additional special care and engineering to extend these layers outward in space and tighten them without tearing. "Some systems will spread these protective layers and tighten them. It's a bit like a sail on a ship, just like how you spread it in the wind," Feinberg said < p > according to NASA, the whole process depends on hundreds of different moving parts, including up to 140 release mechanisms, 400 pulleys, 70 hinge assemblies and 90 cables. In addition, NASA has developed various emergency plans in case the deployment cannot proceed as expected. NASA can choose to resend the command to the telescope in case the first command fails. Engineers also add redundancy to the telescope as much as possible, such as multiple circuits that can perform the same taskTo prevent the main circuit from starting normally < p > but sometimes there is really no backup option. During the whole deployment process, there are more than 300 events that can be called "single point of failure". These deployments must be designed because they cannot increase the probability of success by redundant construction. However, NASA is no stranger to dealing with single point of failure. When perseverance landed on Mars in February this year, there were about 100 single point failures in the landing sequence, but the whole landing process was perfect < p > in addition, NASA and Northrop Grumman have tested various deployments of Weber telescope on the ground in the past two to three years, and conducted complex exercises for the final mission. Before adding each component to the telescope, it was tested dozens of times on the ground. Then, the Weber telescope as a whole was folded and unfolded many times One of the biggest differences between the Weber telescope and its predecessor Hubble Space Telescope is that it cannot be adjusted and repaired. However, NASA did make design improvements to prevent the agency from adjusting the telescope in the future. The back of the telescope includes cross shaped stickers that will serve as targets to help guide the robot. NASA may send maintenance equipment to the Weber telescope in the future to add more propellant to its storage tank and prolong its stay in space. If this happens, these stickers will provide a reference point to indicate where the visiting robot should be connected to fill the propellant < p > however, no one at NASA has considered such a refueling mission. Everyone involved is focused on deployment. Once the telescope is fully deployed in the next two weeks, there is still a lot of work to be done during its deep space journey. NASA will continue to fine tune the lenses of the Weber telescope to ensure that they are aligned as expected. Then, about 29 days after launch, the Weber telescope will start the propeller to enter the final position in deep space < p > < / P > < p > until then, the work of the Weber telescope had just begun. Mission controllers will then test and calibrate all instruments on the telescope to ensure that they work properly. This process will take several months, and the scientific operation plan will start sometime next summer. (small) < / P > < p >