The launch scheduled for Tuesday was postponed to December 25, due to “bad weather conditions,” NASA announced.
The James Webb Space Telescope, the most powerful ever built, will take off next Saturday after more than 30 years of waiting. This jewel of engineering belonging to NASA, will explore the development and extension of the Universe from about 13 billion years ago.
The launch scheduled for Tuesday was postponed to December 25, due to “bad weather conditions,” NASA announced.
The launch was postponed on Tuesday for the third time, this time due to weather conditions in Kurú, in French Guiana.
Here is a summary of this jewel of engineering in five questions:
1. What does it look like?
Its centerpiece is its huge main mirror, 6.6 meters in diameter and made up of 18 smaller hexagonal mirrors. They are made of beryllium and coated with gold to better reflect the light captured from the far reaches of the Universe.
The observatory also has four scientific instruments: imagers to take pictures of the cosmos and spectrometers, which break down light to study the chemical and physical properties of observed objects.
The mirror and the instruments are protected by a huge visor, made up of five superimposed layers. They are the size of a tennis court, thin as a hair, and made of kapton, a material chosen for its resistance to extreme temperatures: one side will be exposed to more than 110 ° C and the other to -235 ° C.
A service module containing the propulsion and communication system will also be on board. In total, the observatory weighs the equivalent of a school bus.
2. Where is it going?
The telescope will be placed in orbit 1.5 million kilometers from Earth, four times the distance from our planet to the Moon.
Unlike the Hubble telescope that revolves around the Earth, James Webb will be in orbit around the Sun. It will evolve in constant alignment with our greatest star and the Earth, “behind” the latter. Your mirror will constantly be with your back to our main star.
It will take about a month to reach this position, called the L2 Lagrange point. At this distance, no manned repair mission can be foreseen, as had been the case with Hubble.
3. How will it be deployed?
Since the telescope was too big to fit on a rocket, it was folded back on itself. A technical limitation that generates the most complicated part of the mission: its deployment in space, the most dangerous ever attempted by NASA.
Approximately 30 minutes after takeoff, the communications antenna and the solar panels that power it will be deployed.
So the extension of the sun visor, until now folded like an accordion, will begin on the sixth day, long after the Moon has passed. Its thin membranes will be guided by a complex mechanism that involves 400 pulleys and 400 meters of cable.
During the second week, it will finally be the mirror’s turn.
Once in their final configuration, the instruments will need to cool down and calibrate, and the mirrors will need to be adjusted very precisely. After six months of setup and procedures, the telescope will be ready.
4. What are you going to do?
James Webb has two major science missions that together will account for more than 50% of his observing time. First, to explore the first ages of the Universe, which go back a few hundred million years after the Big Bang – the Big Bang, the basis of the theory of universal evolution. Scientists want to observe the first galaxies and the first stars in the Universe.
His second major mission will be to study exoplanets, that is, planets around stars other than our Sun, in search of a habitable environment, in particular by studying their atmosphere.
The great novelty of James Webb is that it will only operate through the near and middle infrared. It will be able to see through dust clouds impenetrable to Hubble, which has a small infrared capability but operates primarily in visible and ultraviolet light.
Closer observations, in our solar system, of Mars or Europa, a moon of Jupiter, are also planned.
5. How long have we been waiting for it?
This project was launched in the 1990s, and its construction began in 2004. Its take-off has been postponed many times, initially in 2007, then in 2018 … In particular due to the complexity of its development.
The observatory is the result of an immense international collaboration and also integrates Canadian and European instruments. More than 10,000 people worked on the project, whose budget has skyrocketed, at a cost that is eventually approaching $ 10 billion.
It will work for at least five years and potentially up to more than 10 years. (I)
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