Great new picture of James Webb before the start of the science mission

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On May 9, NASA held a media conference to discuss advances in preparing the James Webb Space Telescope for scientific operations. The host revealed that the telescope was to deliver its first images in mid-July. These footage, which should be spectacular, is eagerly awaited by all researchers. Meanwhile, some photos from photos taken during the mirror adjustment phase have been published.

The James Webb Space Telescope needs no introduction. Launched last December, the $ 10 billion unit is the largest and most powerful astronomical observatory ever launched into space. Its purpose is to collect the light emitted by the first stars and galaxies almost 14 billion years ago, while keeping an eye on possible signs of life. For now, scientists are keeping the identity of Webb’s first official target a secret. Located 1.6 million kilometers from Earth, Webb is considered the successor to the aging Hubble Space Telescope, although its observations will mostly be of a different nature.

Thus, the James Webb telescope has just completed its mirror adjustment phase. After an extensive review, it has been confirmed that the observatory is now capable of capturing sharp and well-focused images with each of its four powerful scientific instruments on board. The team held a series of important decision-making meetings and unanimously agreed that Webb is ready to move on to his next and final round of preparations, called “Science Instrument Commissioning”. This process will take about two months before scientific operations begin this summer.

Unexpected performance

The telescope’s optical performance remains better than the engineering team’s most optimistic predictions. Web mirrors now direct fully focused light, collected from space, into each instrument, and each instrument successfully captures images with the light provided to them. The image quality provided to all instruments is “diffraction limited”, which means that the fineness of visible details is as good as physically possible given the size of the telescope. From now on, as NASA engineers pointed out during the teleconference on May 9, the only changes to the mirrors will be very small, periodic adjustments to the primary mirror segments.

To test the alignment of the mirrors and the various instruments, the researchers pointed the Webb telescope at part of the large Magellanic cloud, a small satellite galaxy in the Milky Way that provided a dense field of hundreds of thousands of stars through all the sensors of the observatory. In fact, such precise points in the sky, already observed by other telescopes (Hubble or Spitzer), are valuable in the astrometric calibration phases, the project engineers explained on 9 May.

Star-studded images of part of the large Magellanic cloud, perfectly focused in the field of view of each instrument. © NASA

The new Webb image, which was sent back to the researchers and completed the adjustment of the 18 mirrors, is surprisingly much more detailed than the previous ones, especially because it uses the coldest instrument, the Mid-Infrared Instrument (MIRI). The new MIRI image thus reveals the chemistry of interstellar gas in unprecedented detail, including the emission of carbon and hydrogen molecules. The latter, called “polycyclic aromatic hydrocarbons”, are considered to be the building blocks of life. When Webb is ready to begin scientific observations, studies like these with MIRI will help provide astronomers with new information about the birth of stars and protoplanetary systems.

Instrument commissioning

Now the team will take about two months to prepare and test the scientific instruments – the so-called “instrument commissioning” – before the first scientific images and Web spectra are released this summer.

Each instrument is a highly sophisticated set of detectors equipped with unique lenses, masks, filters and equipment. The specialized features of these instruments will be configured and operated in various combinations during the instrumentation phase of the instrument to fully confirm their readiness for future missions.

The various instruments, grouped under the name ISIM (Integrated Science Instrument Module), are: (1) a near-infrared camera or NIRCam – supplied by the University of Arizona; (2) a near-infrared spectrograph, or NIRSpec – supplied by ESA, with components supplied by NASA / GSFC; (3) Mid-Infrared Instrument, or MIRI – developed by the European Consortium and European Space Agency (ESA), as well as NASA’s Jet Propulsion Laboratory (JPL); and (4) a Fine Guidance Sensor / Near InfraRed Imager and Slitless Spectrograph, or FGS / NIRISS – provided by the Canadian Space Agency.

Schematic of the James Webb Space Telescope ISIM showing instrument locations. © NASA

As part of the commissioning of the scientific instrument, scientists will direct the telescope to point to different areas of the sky where the total amount of solar radiation hitting the observatory will vary, to confirm thermal stability when changing targets. . In addition, ongoing maintenance observations, every other day, will be used to monitor the adjustment of the mirror and, if necessary, apply corrections to keep the mirrors in their directed position.

Finally, mission engineers will test Webb’s ability to track objects in the solar system, such as planets, satellites, rings, asteroids, and comets. Researchers will focus on ensuring that Webb can do this properly, as the observatory is particularly sensitive to light.

While officials have not yet released information on which commissioning goal Webb will only focus on once its testing work is complete, they stressed that the observatory remains on schedule to begin its expected scientific release this summer.

Source: NASA

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