The James Webb Space Telescope has safely arrived at its destination, and preparations begin to obtain the first image of the farthest universe. The first photo is not expected until April (at least)
The Space Telescope NASA’s James Webb Has Just Arrived at His Final Destination: around a gravitationally special place, in a piece of space known as the second Lagrange point, or L2. The observatory that cost a whopping 10 billion dollars will stay in L2 for at least 20 years.
L2 is on the opposite side of the Earth from the Sun, about 1.5 million kilometers away, or four times the distance from the Moon. There, the combined gravitational pull of the Sun and Earth balances the centripetal force that pulls Webb toward opposite.
Only a handful of space missions have traveled to L2, which is one of the five Lagrange points in the Sun-Earth system. From there, it is possible to observe most of the universe without obstacles.
From L2, James Webb’s tennis court-sized sunscreen blocks the sun, while its 6.5-meter-wide main mirror peers into the darkness of deep space.
The first star to be photographed by James Web
Webb’s optics and instruments will soon cool to around -230C (some sections of the telescope are already at that temperature). When that happens, controllers will turn on the Webb’s infrared camera (NIRCam) to take a picture of a test star to start the big mirror alignment process. But that first image will be totally blurry.
Controllers on Earth need several months to adjust the telescope and calibrate its mirrors until the first focused image is obtained. When they do, it will be a historic moment in astronomical observation.
James Webb’s first focused and useful photo is expected in April. First you have to turn on the four instruments of the observatory and also calibrate your mirrors.
When you get closer to the star, you will see 18 different points of light because the 18 individual mirror segments will not be aligned. Then you have to adjust the mirrors to join all the dots and make a single star.
It’s a long process. It can last up to three months.
The approach involves driving small actuators, or motors, on the back of the 18 segments of the main mirror to harmonize their curvature. The current misalignment, which is measured in millimeters, will be reduced to a measurement in nanometers.
Similar adjustments will apply to the 74 cm diameter secondary reflector which is located in front of the primary mirror and is used to reflect light onto instruments.
James Webb was designed to see the cosmos in infrared light and therefore must maintain constant extreme cold conditions for his hardware.
Infrared light has slightly longer wavelengths than visible light. “Seeing” in the infrared will allow the telescope, for example, to peer through dust to image stars that would otherwise be obscured.
So far, the Webb mission hasn’t made a single misstep. The launch and trip to L2 were uneventful. From Earth, we look forward to seeing its “first light”, the name given to the first telescope image.