NASA merges James Webb telescope for the first time

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The James Webb telescope is assembled for the first time. NASA has combined the two halves of the telescope. The telescope should go into space in March 2021, where it will search for, among other things, ancient galaxies and investigate the atmospheres of discovered exoplanets.

“Bringing the telescope and its scientific instruments, solar shield and spacecraft part together into one observatory is an incredible achievement by the entire Webb team,” said NASA project manager Bill Ochs. He speaks of a milestone for NASA, ESA, the Canadian Space Agency, principal builder Northrop Grumman and other industrial and academic partners.

Technicians combined the halves by means of a crane. The telescope element, including the optical and scientific instruments, was lifted above the spacecraft section, after which the telescope was slowly moved into position so that all contact points were precisely aligned. The observatory is now mechanically connected. The next step in this process is to electronically connect both halves together and test those electrical connections.

James Webb’s collapsible sun shield was already attached to the spacecraft when the two halves were put together. This solar shield is central to a subsequent test procedure, in which technicians will fully unfold the five-layer shield. That test is crucial. If the unfolding in space does not go well, this may mean that the mirrors and the scientific instruments are getting too hot. The shield is intended to block the infrared light from the sun, earth and moon; due to the sun shield, the bottom of the spacecraft is 85 degrees Celsius, while the other side, where the mirror and instruments are located, is more than 300 degrees colder.

The James Webb telescope should have already floated in space, but the launch has been postponed several times, partly due to technical problems. The observatory is lifted by an ESA Ariane 5 rocket and consists of a 6.5-meter folding mirror formed by eighteen hexagon-shaped, gold-coloured mirror segments. These elements and the secondary mirror have to be put in exactly the right place to make it into a whole. In the past, the Ariane 5 was chosen, which means that these foldable elements are necessary to fit James Webb into the rocket.

The telescope is placed in space near the so-called second Lagrange point, or L2. That point is located at a distance of 1.5 million kilometers from Earth. So James Webb doesn’t orbit the Earth like the Hubble telescope; it orbits the sun at the L2 point. The telescope to be launched in 2021 focuses on infrared light; if James Webb had been placed in orbit at an altitude of roughly 540km like Hubble, targeting wavelengths in the infrared part of the spectrum would have been a lot more problematic. The Hubble telescope, on the other hand, is designed to look at wavelengths in the ultraviolet, visible and near infrared spectrum.

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