Webb Space Telescope and the Merry Machine Told by the French Who Made It

This time, there he is! The telescope The James Webb Space Telescope, or “Webb”, is in Kourou and will be launched by a rocket Ariadne 5 The December 24 [la date de lancement peut encore changer, NDLR]. Yes, with a delay of more than 10 years compared to the first estimates! Yes, its cost has been multiplied by 10! But the scientific harvest promises to be exceptional.

Webb will make it possible to scan areas Universe Notes virgins thanks so Mirror With a diameter of 6.5 meters, it is the largest space ever spread out Four tools watch inInfrared : Near CameraAnd the NeresAnd the NIR and MIRI (“IR” sounds come from “infrared”).

Meri Tool Explanation. © CNRS

Webb, the main task of NASA and European space agencies (ESA) and Canadian (CSA), from Hubble Space Telescope For more monitoring inUniverse. The speed of light obliges him, and therefore he will consider earlier in history, even the moments when he is the first galaxies The first stars were formed. But it will also transfer a file Spitzer Infrared Space Telescope to check ambiance Exoplanets, stars, planetary systems in formation, the evolution of galaxies …

In short, everything fields of astrophysics You will benefit from it. We are one of more than 1,200 scientists from 14 countries who contributed to the development of JWST. In France, we mainly participated in the development of the Miri instrument, which is the only instrument among the four that works in the so-called “thermal” infrared field. watch in wavelengths between 5 and 28 micrometerwill be better able to monitor Gas And dust is in bodies much cooler than stars like us Sun. It would allow, for example, to see the young stars still deeply buried in the Cloud The gas and dust they form in. Miri will also be the primary complement to NIRCam to identify the first galaxies in the universe.

Epic telescope web

Initially, it was not certain that a thermal infrared instrument would be part of the JWST instrument cluster (called ” Next generation space telescope in time). NASA and the European Space Agency must be convinced of the scientific importance and feasibility of such a device. one of us (Pierre Oliver Laggage) was part of a small group ofastrophysicists Who campaigned in Europe and the United States for such a tool.

That was… in the late ’90s. The launch of the.. the launch of the.. the take off of the web telescope Then 2007 was planned. But Webb launch postponed Many times, the Merry Machine saga actually explains the reasons for these consecutive delays.

Webb will be in orbiting 1.5 million km from Earth, which is 4 times the distance between Earth and the Moon. It will not be possible to go and fix it if a problem occurs, as it was done for Hubblewhich orbits “only” 570 kilometers from Earth: when Hubble was turned on, the quality of the images proved very disappointing, but the installation by astronauts Optical corrector made it possible to restore the expected image quality.

For Webb, we have no room for error – hence the importance of pre-launch design and testing!

MERI, a sophisticated instrument for the exoplanets

Mary It consists of two main parts: the “imaging device”, which allows you to take pictures (this is the part called “Maryam”and one spectrometerwhich makes it possible to study the light received as a function of wavelength – thus, for example, to determine which chemical elements present in the object being observed (that is “Ms”). The performance of these tools is placed in lobby Of the largest space telescope in operation would be unprecedented.

Meaning, to study outer planetsWebb’s launch delays are good news. In fact, the field has exploded in recent decades and we currently have a wealth of exoplanets to monitor, including rocky planetswhich was not known in 2007.

We are now studying a lot outer planets by the method known as Transit »: We check for small differences in a file brightness A distant star due to the passage of an outer planet surrounding it. So Merry was “enhanced” to use this method of crossing. It is a matter of reading only a small part of the detector, in order to do it very quickly without saturating the detector. Essentially, we’re slightly “skew” from the primary purpose of Webb, which is designed to monitor faint or very distant objects, to take advantage of its greater sensitivity.

Mary also has Coronagraphs Historically used to observe the sun’s corona by masking the super-bright disc that prevents seeing surrounding details, the crescentic vertebrae have been adapted for stargazing, thus marking any exoplanets that may be nearby. Merry bears a classic vertebra (known as “de Lyot”) and three vertebrae. Corona with stage mask ‘, very effective, which will be sent into space for the first time.

From cradle to take off

After several years of preliminary studies, in 2004 the French contribution to Merry was approved by CNESand CEA and CNRS.

Mirim’s photographic flight model was assembled and tested at CEA Paris-Sclay in 2008 and 2009; A test platform that can reproduce the vacuum and cold conditions Mirim will encounter once in space, has been specially developed for the occasion. In 2010, Mary was sent to Rutherford Appleton Laboratory In England to be coupled to the other part of the Merry, the MRS spectrometer, then tested in a vacuum chamber large enough for the complete instrument.

In 2012, Mri was sent to Goddard Space Center NASA, near Washington, where it has been linked to the three other JWST instruments. Three rounds of cryogenic testing followed between 2012 and 2016.

18 hexagons of the telescope’s primary mirror were also assembled Goddard Space Center From November 2015 to February 2016. The instruments were installed on the back of the telescope’s primary mirror and the assembly was sent in 2017 to Houston for testing, as the test station at Goddard Space Center It was not large enough to accommodate the telescope. The CEA team was on site to conduct the tests when Hurricane Harvey He fell. more fear of harm; Just a few nights in the lab without being able to go back to the hotel and a Sentences Totally drowned!

Assembling the telescope (mirrors and gold instruments, including MIRI) and the heat shield (which looks like foil or plastic and is deployed at 0:28 in the video). © NASA Goddard

Once the tests were completed, we “dropped” Merry for his flight to Northrop Grumman’s California headquarters, where he arrived in early 2018. There, the telescope was attached to a satellite and large thermal screens that would block sunlight, Earth and the moon to reach the telescope. This would then be able to passively reach a temperature of about 45 K (-228 °C), which is necessary so as not to interfere with observations in the infrared.

Finally, at the end of September 2021, Webb left California to Kor He arrived after a 16-day boat trip that took him across the Panama Canal (which was banned a few months ago!).

Ready to take off … and start with tests and scientific observations

The space adventure will then begin on December 22, 2021, with a series of tests in the sky that will last 6 months. Then, at the end of June 2022, scientific exploration will be able to begin, after three decades of development.

A small portion of the observation time is devoted to the astrophysicists who were involved in developing the instruments. In this context, we coordinate the observations that will be assigned to the exoplanets, Supernova 1987a, and two photozones.

Most of the observation time will be “open”: every year during the 5-10 years of Webb’s life, several calls are scheduled for Webb use. The first call was made in 2020. More than 1,000 applications were submitted, involving more than 4,000 astrophysicists around the world. The number of observation hours required is much higher (4 to 5 times) than the number of hours available and was chosen by committees of scholars. It is gratifying to see that Meri is the second most sought after machine. Well done for insisting that it “come aboard” the Web!

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