[우주를 보다] ‘Twenty-nine days of travel on the brink’.. James Webb’s difficult journey

▲ ‘The Eye of the Next Generation’ The James Webb Space Telescope is starting a ’29-day cliff-edge journey’ towards its destination, L2, after it was separated from the Ariane 5 rocket. NASA TV

NASA’s next-generation space telescope, which cost 10 billion dollars, has finally been launched after 14 years of tardiness, but it will take some time before the promising scientific mission begins.

The mission of the James Webb Space Telescope (JWST), which was launched from French Guiana on Christmas 25th aboard the Ariane 5 rocket, is to uncover the secret of the origin of the universe, a long-cherished dream of mankind. To this end, JWST plans to look into the early universe 13.5 billion years ago, and also to search for life on nearby exoplanets.

All of these missions are directly related to the primal problem of when, where, and how we humans got here. However, in order to carry out this mission, the members of the JWST team must maintain patience for a considerable period of time. This is because there are many things that need to be solved and performed before the web starts full-scale exploration.

JWST is directed at the Sun-Earth Lagrange point 2 (L2), 1.5 million kilometers (about 4 times the Earth-Moon distance) away from the planet Earth, opposite the Sun, in the direction of the current Mars. This is a gravitationally stable point where the gravitational force of the sun and the earth are balanced, and the web can orbit the sun without a separate power source. It will take the Web 29 days to get there, and in the process it will have to go through a number of difficult rites of passage that will make you sweat.

Mike Menzel, web engineer at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said: “There are about 50 major deployments that the Webb telescope will perform, 178 release mechanisms deploy 50 related devices. “As he revealed in his ’29 Days on the Edge’ published in October, he said, “This deployment is the most complex spacecraft activity I’ve ever done, and none of it should fail.” it was

The web has already achieved several major milestones. For example, about 30 minutes after takeoff, solar panels are deployed and begin to absorb solar energy. And last night, the engine was injected for 65 minutes to correct the course, and it was on the orbit towards L2.

The following is a summary of the major steps to be taken, and the timeline given is approximate. (See NASA’s web deployment site for details)

A day after launch, the Web will rotate its high-gain antenna towards Earth, further facilitating communication with ground control. The next day, the spacecraft performs another engine injection to correct its orbit towards L2. And three days after launch, a pallet is lowered that holds the web’s massive sun screen (a five-tier structure designed to keep infrared telescopes and equipment cool).

The five-sheet sun screen, when fully expanded, was the size of a tennis court, and folded flat, mounted inside the rocket’s payload fairing. The process of unfolding this is incredibly complicated. Inside the structure are 140 release devices and 70 hinge assemblies, 400 pulley devices, 90 cables and 8 deployment motors, all of which must work for the 5 rolls to deploy as planned, NASA officials explain.

On the 5th day after firing, the shielding protective cover is removed, and the pedestal is extended a day later. Deployment of the sun shield must be completed within eight days of launch, at which point team members begin shifting focus to the optics.

About 10 days after launch, Webb will deploy an auxiliary reflector 0.74 m wide. This secondary reflector is the second reflector that deep space photons strike the telescope’s main reflector.

Then it’s when the web’s 6.5m wide primary mirror shines. The main reflector, composed of 18 hexagonal mirrors like a honeycomb, was launched in a folded state like a sun shield. 12 to 13 days after launch, the mirror’s two side ‘wings’ unfold and lock in place to become the full size of the main reflector.

At this point, the web is finally complete. The giant space observatory arrives at its destination in less than two weeks, and 29 days after launch, it fires another engine injection and enters orbit around L2, where another ramp-up procedure begins.

▲ An image of the James Webb Space Telescope (JWST) posed at Lagrange 2 at 1.5 million km, which is four times the Earth-Moon distance. It will follow in the footsteps of the Hubble Space Telescope and take mankind back to the primordial universe. NASA

For example, two to three months after launch, the team aligns the single main reflector mirrors into a single collecting surface. This will be a laborious and time-consuming task, as mirror alignment must be perfect to an accuracy of 150 nanometers (one billionth of a meter). For reference, a sheet of paper is about 100,000 nanometers thick.

“One of our scientists calculated that the mirror must move slower than the grass grows,” said Jonathan Gardner, web chief scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

In the process, the team will also test and calibrate the Web’s four scientific instruments, which will be arduous as well. The goal is to embark on a regular scientific mission six months after launch. “We’re looking at the end of June,” Gardner predicts.

Webb’s observation time, like NASA’s Hubble Space Telescope, is distributed among various projects selected through peer review by scientists. “It will be a tough marathon,” Gardner said, adding that “the first year’s worth of web projects have already been decided, so the new observatory will start working as soon as it’s ready.”

Columnist Lee Kwang-sik


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