Thousands of astronomers are holding their breath. The Ariane 5 rocket, which will carry the James Webb Space Telescope (JWST), arrived Thursday on its launch pad from the Guyanese Space Center, for a launch scheduled for Saturday morning. This was the last major step to be taken before takeoff scheduled for 1:20 p.m. (Paris time). The JWST will then be the most advanced cosmos observation instrument to be put in space. He will be responsible for tracing the origins of the Universe and exploring extrasolar planets similar to Earth.
After several days of bad weather causing the postponement of final operations, the sliding doors of the final assembly hangar have been raised under the sun. To unveil the rocket, placed on its “table”, an enormous steel platform, with sides browned by the fires of previous launches.
480 tons of powder
Until the supported by jacks, the whole was placed on railway bogies, to take the 2.8 km of double track bringing it to its position at the firing point. A truck, ballasted with 14 tons to ensure the grip of its wheels, then got down to the task of towing everything, weighing 1,500 tons, at the speed of a man in walking, for about an hour. And in the rain, which could not help but come back.
At this point, the rocket cannot take off yet, but can already turn into fireworks. “Thank you for putting your cell phones in airplane mode”, to avoid any odds, warns Bruno Gérard, director of Arianespace Guyane, at the foot of the machine.
The rocket is indeed already equipped with its two booster thrusters, long tubes attached to the main body, containing a total of 480 tonnes of powder, and providing 90% of the thrust needed for Ariane 5 to tear itself away from the attraction. earthly.
Once arrived at its launch pad, the rocket will be filled, approximately 4:30 before H hour, with its two propellants, liquid hydrogen and oxygen, the mixture of which will start the combustion of the main engine.
Time machine
This “generalist observatory”, unequaled in size and complexity, has an immense mirror, made up of 18 hexagonal segments, measuring 6.5 meters in diameter, or nearly three times that of Hubble. It is so big that it had to be bent to fit in the rocket fairing, like an origami. Once in space, the challenge will be to fully deploy its mirror and its sun visor, as large as a tennis court, before calibrating its four instruments.
The “monster” will be placed in orbit around the Sun, 1.5 million kilometers from Earth, well beyond the limits of its big brother, which has been operating at an altitude of 600 km since 1990.
Carefully chosen, this destination called the Lagrange 2 point, ensures it a position “with the Earth, the Sun and the Moon all on the same side of its sun visor, which places it in the dark and very cold” , explained Pierre Ferruit. He will thus be able to work sheltered from disturbances, an essential condition for his visual acuity, deployed in the infrared domain: a wavelength invisible to the naked eye that Hubble could not see.
Where Hubble was able to observe the Universe up to 500 million years after the Big Bang, its successor can hope to go back up to 200 million years “only” after the explosion which gave birth to the Universe, he 13.8 billion years ago. A huge gap to understand this mysterious period when the Universe was just emerging from its dark ages.