Author: Marcia Rieke, Professor of Astronomy at the University of Arizona.Originally published on dialogue

The James Webb Space Telescope was launched on December 25, 2021. Astronomers hope to find the earliest galaxies in the universe, search for Earth-like atmospheres around other planets, and accomplish many other scientific goals.

I’m astronomer and Chief Researcher of Near Infrared Camera – or Near infrared camera In short-board the Webb telescope. I participated in the development and testing of my camera and the entire telescope.

In order to penetrate into the universe, the telescope has a very large mirror, which must be kept extremely cold. But sending such a fragile device into space is not easy. My colleagues and I had to overcome many challenges when designing, testing, and quickly launching and calibrating the most powerful space telescope ever built.

Young galaxies and alien atmospheres

The Webb Telescope has a mirror over 20 feet and a sun visor the size of a tennis court, which can block solar radiation and Four independent cameras and sensor systems to collect data.

It works like a satellite dish. The light from the star or galaxy will enter the mouth of the telescope and be reflected from the main mirror to the four sensors: Near infrared camera, To take images in the near-infrared region; this Near infrared spectrometer, It can divide the light from the selected light source into their constituent colors and measure the intensity of each color; this Mid-infrared instrument, It takes images and measures mid-infrared wavelengths; and Near-infrared imaging seamless spectrometer, It splits and measures the light of any object the scientist points to the satellite.

This design will enable scientists to study how stars form in the Milky Way and the atmospheres of planets outside the solar system. It may even be possible to figure out the composition of these atmospheres.

Ever since Edwin Hubble proved that distant galaxies are like the Milky Way, astronomers have been asking: How old is the oldest galaxy? How were they formed in the first place? How do they change over time?The Webb telescope was originally called “The first light machine” Because it aims to answer these questions.

One of the main goals of the telescope is to study distant galaxies near the edge of the observable universe. It takes billions of years for the light from these galaxies to travel through the universe and reach the earth. I estimate that my colleagues and I will use the images collected by NIRCam to show the proto-galaxies formed only 300 million years after the Big Bang—their age was only 2% of their current age.

Finding the first stars formed after the Big Bang is a difficult task, and the reason is simple: these proto-galaxies are so far apart that they look dim.

Weber’s mirror consists of 18 separate parts that can collect more than Six times the light of the Hubble Space Telescope mirrorObjects in the distance also look very small, so the telescope must be able to focus the light as closely as possible.

The telescope must also deal with another complex problem: due to The universe is expanding, The galaxy that scientists will study with the Webb telescope is moving away from the earth, and the Doppler effect is beginning to take effect. Just as the sirens of an ambulance move down and become deeper as it passes by and starts to move away from you, the wavelength of light from a distant galaxy also moves down from visible light to infrared light.

Weber detects infrared light-it is essentially a huge thermal telescope. In order to “see” faint galaxies under infrared light, the telescope needs to be extremely cold, otherwise it can only see its own infrared radiation. This is where the heat shield comes in. The heat shield is made of thin plastic coated with aluminum.It has five layers thick, 46.5 feet (17.2 meters) long and 69.5 feet (21.2 meters) wide. Keep the mirror and sensor at minus 390 degrees Fahrenheit (minus 234 degrees Celsius).

The Webb telescope is an incredible engineering feat, but how can such a thing be safely sent to space and guaranteed that it will work?

Test and rehearse

The James Webb Space Telescope will revolve Million miles from the earth – Approximately 4,500 times farther than the International Space Station, and too far to be serviced by astronauts.

In the past 12 years, the team has tested the telescope and instruments, shook them to simulate rocket launches, and tested them again. Everything was cooled and tested under extreme orbital conditions. I will never forget that my team tested NIRCam in a dark room designed for the Apollo lunar rover in Houston. This is the first time my camera has detected the light reflected from the telescope mirror, and we are so happy that we can’t be happy anymore-even though Hurricane Harvey is fighting with us outside.

After the test, there was a dress rehearsal. The telescope will be controlled remotely via commands sent by the radio link. But because the telescope is too far away—it takes 6 seconds for the signal to propagate in one direction—there is no real-time control.So in the past three years, my team and I have been Space Telescope Science Institute In Baltimore, and run drill missions on the simulator, covering everything from launch to regular scientific operations. The team even practiced dealing with potential problems that the test organizers had thrown at us and lovably called “abnormalities.”

Need some alignment

The Webb team has been rehearsing and practicing until the release date, but our work is far from complete.

We need to wait 35 days for the parts to cool down after launch before starting calibration. After the mirror is unfolded, NIRCam will capture a high-resolution image sequence of each mirror segment. The telescope team will analyze the image and tell the motor to adjust the segmentation in billionths of a meter. Once the motor moves the mirror into place, we will confirm that the telescope alignment is perfect. This task is so critical that there are two identical copies of NIRCam on board-if one fails, the other can take over the alignment.

This alignment and checkout process should take six months. Once completed, Webb will start collecting data. After 20 years of hard work, astronomers will finally have a telescope that can observe the farthest and most distant part of the universe.