Yahoo! News Successful deployment of the world's most complex telescope-First Light as early as spring
An imaginary view of the James Webb Space Telescope with a telescope and sun shield (C) NASA GSFC / CIL / Adriana Manrique Gutierrez
NASA and others launched the "James Webb Space Telescope (JWST)" on December 25, 2021. [Photo] A huge silver sunscreen that NASA describes as "SPF 1 million sunscreen". Compared to the humans standing in the vicinity, JWST, whose size can be understood, shows various times and appearances of the universe, such as the light of stars and galaxies born in the early universe, celestial bodies in the solar system, and planets outside the solar system. It can be observed and is expected to bring many new discoveries. In Part 4 of this series, we will explain the various cutting-edge technologies that have been invested to bring about such discoveries, as well as the current status and future plans. State-of-the-art technology that realizes the world's first observation In Part 2 of this series, JWST will observe the universe centered on infrared rays, unlike Hubble, and in Part 3, what kind of discoveries are expected by looking at infrared rays. I've seen if it can be done. To achieve this, JWST has invested a lot of cutting-edge technology. After all, JWST's distinctive shape is eye-catching. It looks like a sailing ship with a golden sail on a silver hull. The golden part at the position of the sail is the primary mirror of the telescope. With a diameter of 6.5m, it is about 2.5 times the diameter and about 6 times the area of the Hubble, making it the largest space telescope ever launched. This realizes a large light collection capacity. It has become possible to observe the universe far in the past than Hubble. The primary mirror consists of 18 hexagonal mirrors, each of which is made of lightweight and robust beryllium. However, since beryllium does not easily reflect infrared rays, the surface is coated with a thin layer of gold that reflects infrared rays well. Therefore, it shines golden. The silver part on the hull of the sailing ship is the "sun shield" that protects the telescope from heat such as the sun and cools it. In order to see the faint light from distant celestial bodies and celestial bodies hidden in dust, it is necessary to capture the light with as high sensitivity as possible. For that purpose, it is necessary to prevent the heat radiated not only from the sun but also from the earth and even the spacecraft itself, and to cool the telescope and equipment to near absolute zero. Until now, infrared space telescopes have used "liquid cooling" that uses a coolant such as liquid helium. However, there is a drawback that the telescope cannot be used when the coolant is exhausted. Therefore, JWST adopted a mechanism to cool the telescope by expanding the shield and blocking the heat from the sun, the earth, and the aircraft. This is the first infrared space telescope in history that does not use coolant. The shield consists of five layers of aluminum-coated Kapton sheets, which NASA describes as "one million SPF sunscreens." Its size is as large as 20m x 12m. This makes it possible to keep the telescope and equipment at 50K (-223 ° C) at all times. Both the telescope and the sun shield are folded and compact to be mounted on a rocket at the time of launch, and are designed to be deployed in outer space. The mechanism for opening is extremely complicated, and there are 344 places where if any one fails, it will affect the whole. For JWST, if seeing the beginning of the universe and the traces of life is a challenge in science, transforming from the form at the time of launch to the form for observation can be said to be a challenge in engineering. Behind the telescope, there is a box-like part called "Integrated Scientific Instrument Module (ISIM)", which is a collection of devices such as cameras. Here you will find "Mid Infrared Equipment (MIRI)", "Near Infrared Spectrograph (NIRSpec)", "Near Infrared Camera (NIRCam)", "Fine Guidance Sensor / Near Infrared Imager Slitless Spectrograph (FGS)" -NIRISS) "and four devices and their associated subsystems are housed. Along with the telescope, these devices also have a wider observable wavelength range than the Hubble, and their sensitivity is greatly improved, which is a major factor in achieving their outstanding performance. On the other side of the telescope across the shield is the spacecraft bus, which houses solar cells, attitude control equipment, communication equipment, command data processing equipment, thrusters (propulsion systems), and thermal control equipment. The launched JWST will be placed in a halo orbit around the Lagrange point L2 of the Sun-Earth system, about 1.5 million km away from the Earth. This location is so far away from the Earth and the Moon that it has the advantage of being unaffected by the infrared rays emitted by them. Also, because the positional relationship between JWST, the Earth, and the Sun is always the same and aligned, it is possible to point the solar cell and communication equipment toward the Sun and the Earth while always pointing the telescope at space. This also improves the accuracy of celestial body introduction (pointing). It achieves higher observation efficiency than the Hubble Space Telescope orbiting the earth. However, on the other hand, since the distance is long, it is difficult to communicate and transmit observation data. Also, the L2 halo orbit is not completely stable, so thrusters must be injected regularly to maintain the orbit. The maximum operating period mentioned above is about 10 years, which comes from the amount of fuel loaded for that purpose. The Hubble Space Telescope was also able to use the Space Shuttle to send astronauts for repairs and refurbishment to improve performance, but JWST is so far away that it is difficult to go. However, in recent years, satellites that refuel and repair old satellites are appearing, so it may be possible to realize unmanned refueling and repair missions. The JWST, which was launched on December 25, 2021, is now on the orbit toward the L2 point for safe observation. The high accuracy of the rocket's orbit insertion was a bonus that the operating life of JWST was slightly extended. After separation from the rocket, JWST began by deploying solar cells. Next, develop a pallet on which the sun shield etc. can be placed. The deployment of the sun shield began on January 1st, and proceeded smoothly with confirmation on the way, and the deployment was completed on January 5th. And from January 6th, the deployment of the telescope part will start. It started with the deployment of the tripod that supports the secondary mirror, the left side of the primary mirror on the 8th, and the right side on the 9th. In this way, he successfully completed a major technological challenge in the history of space exploration. As of January 17, each device is normal, and it is sailing smoothly toward the L2 point while making fine adjustments and orbit corrections for each mirror. The arrival of the L2 point in the halo orbit is scheduled to be about one month after the launch. After that, it took several months to adjust the telescope and calibrate the scientific instruments. If all goes well, the first image shooting "First Light" will be held about 5 to 6 months after the launch. Its first target will be selected by consideration by NASA, ESA, CSA and scientific community participants participating in the project, as well as the Hubble Space Telescope imaging process. And at the earliest, scientific operation will start even before summer. The first stars born in the universe, galaxies, the birth of stars and planets, another earth, and the origin of life-the greatest challenge of the space telescope that human beings can have today, approaching the many mysteries hidden in the universe. Will start. References-NASA's Webb Telescope Launches to See First Galaxies, Distant Worlds | NASA-NASA's Webb Telescope Launches to See First Galaxies, Distant Worlds-Science Themes --Webb / NASA-Observatory --Webb / NASA-FAQ Full General Public Webb Telescope / NASA Shinya Torishima Shinya Torishima Author Profile Space development critic and space development historian. Member of the Space Authors Club. He covers various things related to space, from the latest news in space development and astronomy to history, and writes articles and articles. He also has many commentary on newspapers, television and radio.
Shinya Torishima