NASA refines the instruments of the James Webb telescope to revolutionize its observations

Last week, the James Webb Space Telescope successfully completed its alignment and calibration phase of its 18 mirrors and sent its first unified image of a distant star.

This action was the first adjustment of its instruments to have the telescope fully active from next June. After reaching the main milestone of aligning the telescope with the NirCam instrument, a near-infrared camera, the team of scientists operating the space telescope is beginning to tune other key instruments to see what has never been seen before in the Universe.

But the observatory still has four other instruments that it must be able to switch between with perfect alignment to obtain clear images of distant objects. The work will begin with the guidance instrument (called Fine Guidance Sensor or FGS) and then extend to the other three instruments, said a current NASA communication. Webb engineers expect this process, called “Multi-Instrument, Multi-Field Alignment (MIMF)”, to take 6 weeks to complete.

Webb should complete its start-up period around June, six months after its launch on December 25 on an ambitious mission to observe the universe from deep space and collect data on objects ranging from exoplanets to galaxies.

Camera change

When a terrestrial telescope changes cameras, sometimes the instrument is physically removed from the telescope and a new one is installed during the day when the telescope is not in use. If the other instrument is already in the telescope, there are mechanisms to move part of the telescope's optics (known as a collection mirror) into the field of view.

“In space telescopes like Webb, all cameras see the sky at the same time. To change a lens from one camera to another, astronomers point the telescope to place the lens in the other instrument's field of view. After MIMF, Webb's telescope will provide good focus and sharp images on all instruments,” explained Jonathan Gardner, deputy principal scientist for the Webb project at NASA's Goddard Space Flight Center in Maryland.

“In addition, we need to know precisely the relative positions of all fields of view. Over the past weekend, we mapped the positions of the three near-infrared instruments relative to the guide and updated their positions in the software we used to point the telescope. At another milestone of the instrument, FGS recently achieved fine guidance mode for the first time, blocking a guiding star using its highest level of accuracy. We have also been taking dark images to measure the response of the reference detector when light does not reach them, an important part of the instrument calibration,” added the expert.

The goal of the new lineup, Gardner said, is to “provide good focus and sharp images on all instruments” while knowing the relative positions of each instrument's field of view. The last instrument to be aligned will be the Mid-Infrared Instrument (MIRI), as it is waiting for the ability of a cryogenic cooler to bring it to its operating temperature of minus 448 degrees Fahrenheit (minus 267 degrees Celsius). Interspersed with the initial observations of MIMF, the two stages of the cooler will be switched on to bring MIRI to its operating temperature. The final stages of MIMF will align the telescope for MIRI.

Gardner also explained how instruments will work together to observe a goal. “With parallel scientific exhibitions, when we point an instrument to a target, we can read another instrument at the same time. Parallel observations don't see the same point in the sky, so they provide what is essentially a random sample of the universe. Parallel data allows scientists to determine the statistical properties of the galaxies that are detected,” Gardner concluded.

If we ask ourselves whether all instruments can see the sky at the same time, can we use them simultaneously? The answer is yes! With parallel scientific exhibitions, when we point an instrument to a target, we can read another instrument at the same time, NASA experts say.

Parallel observations don't see the same point in the sky, so they provide what is essentially a random sample of the universe. With a large amount of parallel data, scientists can determine the statistical properties of the galaxies that are detected. In addition, for programs that want to map a large area, much of the parallel images will overlap, increasing the efficiency of Webb's valuable dataset.

With the culmination on the 11th of the “critical” stage of fine calibration in the telescope alignment, the team has managed to completely align Webb's main imager, the camera for the near infrared, with the mirrors of the observatory.

Following the success of this first key phase, the new space observatory is able to successfully collect light from distant objects and send it to its instruments seamlessly, noted NASA, which collaborates on this mission with the European Space Agency (ESA) and the Canadian Space Agency. An example of this is an image sent from Webb that shows a star named 2MASS J17554042+6551277.

Last February, the telescope had already obtained its first images, of lower quality, and in that case of HD 84406, after taking off from Earth on December 25 and reaching its final position almost a month later. NASA also published a photo of a “selfie” from the telescope showing the 18 segments of the primary mirror picking up the light of the same star in unison. The largest space science observatory in the world is still several months away from being ready to be ready, as Thomas Zurbuchen, NASA briefing pointed out, to be able to “see the universe as we have never seen it before.”

What distinguishes James Webb from previous generations of telescopes is that he will observe the universe in the infrared spectrum, so he can observe the first galaxies, the ones closest to the time of the Big Bang.

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