It will be necessary to activate more than 150 mechanisms from the earth without any possible misstep."Only" so that the James Webbb Telescope (JWT) unfolds once in space, he who will embark folded from the Ariane 5 rocket.
This step alone shows all the complexity of the launch of the largest and more powerful telescope ever sent to space.A sun visor as large as a tennis court, a primary mirror 6.5 meters in diameter, composed of 18 hexagonal segments made up of Béryllium and covered with a golden film ... The JWT is "undoubtedly the machineThe most complicated that humans have built, "says German astronomer Markus Kissler-Patig, head of management" science "of European spatial agency (ESA), one of the three involved in this mission with the ASC (Canadian) and especially NASA (American), which is in charge.
A jewel of technology at 10 billion euros in the hands of Europeans
It is this Saturday that we will have to hold your breath.After several postpones, this is the last date arrested by NASA for the launch of the JWT, encapsulated in the cap at the top of the European rocket Ariane 5 which will send it from Lecentre Spatial Guyana (CSG) to Kourou.Takeoff scheduled at 9:20 a.m. local time, 12:20 p.m. on the Greenwich meridian.
A formality for the European rocket?Ariane 5 is in any case far from novice with his 112 flights on the clock, who make him "the world leader in heavy launchers, says Daniel de Chambure, engineer and manager of the adaptation of Ariane 5 for the JWST mission.A little more after her last flight, for which Ariane 5 sent to the geostational transfer orbit more than ten tonnes of useful loads.A record.»»
With the JWT, we are on 6.5 tonnes of useful loads.But what a payload!The space telescope, presented as Hubble's successor, has been imagined since 1989 and has required $ 10 billion in investments.And expectations are colossal. Avec sa capacité à voir dans l’infrarouge proche et moyen, le James Webb représente un « tel bond en avant»» pour l’astronomie « qu’il sera forcément à l’origine de découvertes et que les plus belles sont celles qu’on n’imagine pas encore»», glissait en juin Perre Ferruit, coresponsable pour l’ESA de la mission.This gives an idea of the pressure on the shoulders of more than 100 experts present at the CSG, in recent weeks, to prepare for this launch.
Already several hot strokes
Hot strokes will not start on Saturday.Daniel de Chambure cites a first: transport by boat from the telescope from Long Beach (California), from where he left on September 26, to Kourou, where he arrived on October 12.A cruise of about 10.000 km, passing through the Panama Canal, which the JWT made in a container specially designed for him.Keeping from the slightest contamination, whether dust, organic molecules or clothing fibers.In short, everything that is likely to deposit on one of its two mirrors (secondary and primary in the 18 hexagonal segments) and which could harm the quality of its observations.
Daniel de Chambure fait de cette « nécessité de maintenir en permanence le James Webb Telescope dans une atmosphère ultrapropre»» l’une des complexités de la mission.Not only during his boat transport, but also throughout his preparation in the final assembly building (BAF), where he spent his last weeks on Earth. Au point de l’avoir placé « sous une atmosphère surpressurisée dans une sorte de tente délimitée par des rideaux [de 12 mètres de haut] et dans laquelle les intervenants entrent par un SAS et en combinaison intégrale»», raconte l’ingénieur de l’ESA.In other words, a white room in the white room, the BAF having itself been prepared to be rid of all visible dust and organic molecules in suspension before welcoming the JWT.
Folded and encapsulated at the near 8 mm in the rocket cap
Cleanliness was not the only challenge in recent weeks.Another, just as colossal, was to be able to bring the telescope into the launcher.No choice: we had to fold it. « A la manière d’un origami»», décrit-on à l’ESA.Until it only forms a rectangle 10.66 m high and 4.5 m wide. « Il occupe toute la coiffe avec des marges d’espaces qui ne dépassaient pas les 8 mm»», raconte Daniel de Chambure.This encapsulation was successfully carried out last Friday.A week earlier, the telescope found itself suspended from a cable 40 meters high before being delicately placed to the top of the Ariane 5 rocket.Another delicate operation.
The James Webb Telescope and its launcher will be transferred on the shot this Wednesday, indicates ESA, and then not move to takeoff, Saturday. « La phase de lancement sera courte, 27 minutes précisément»», reprend Daniel de Chambure.This step includes takeoff, the separation of the rocket with its propellants, then the capsule with the rocket, and finally the telescope with its capsule.The first signals of the JWT captured from the earth are expected in the 30th minute after takeoff.
A month to get to your destination ... and deploy
Will it finally be time for the teams of the three space agencies to blow?No way.The JWT will then only be at the very beginning of a long journey of 1.5 million kilometers to the point of Lagrange L2, where it is expected that it is placed in orbit around the sun.Count for about four weeks, during which the James Web Telescope should not be content to move forward.He will also have to deploy.We then come back to the 150 mechanisms which must be triggered without false note.Starting with the solar panels, 31 minutes after takeoff, which will supply the telescope instruments.
Then, "the sequence will begin with the deployment of the sun visor, describes Catarina Alves de Oliveira, head of scientific operations of ESA.First of all of the two structures that protect him, then from the sun visor in itself.Before, finally, to ensure the right tension [stretching] and separation of the five layers of insulation which compose it.»» Ensuite, il sera temps de s’attaquer aux deux miroirs. D’abord « en déployant le support du miroir secondaire, puis des deux ailes latérales qui composent le miroir secondaire»», reprend Catarina Alves de Oliveira.
Fully operational in six months
All these operations are at risk, concedes the scientist of the ESA, "but they were prepared and repeated with meticulousness on the ground, she assures.And, once the webb in space, we will proceed with caution, taking all our time.»» Une fois à destination et déployé correctement, on pourra alors dire qu’il a fait le plus dur.It will still remain to calibrate the telescope and its instruments by exercising it on several targets.A phase that should last five months.In other words: the first images of a fully operational James Webb are not expected for six months.
Hoping that they are the first of a very long series, Hubble's big brother being planned to operate five years.At least at least because it takes fuel to operate at least double.
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