October 2, 2022

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Evolution of Infrared Space Telescopes

Comparing the stunning Webb Space Telescope images with other infrared observatories

The evolution of infrared astronomy, from Spitzer to WISE to JWST. Credit: Andras Gaspar

The images released by the James Webb Space Telescope Team (JWST) last week aren’t official “first light” images from the new telescope, but somehow, they look the same. These stunning views provide the first indications of just how powerful JWST is, and how much infrared astronomy is about to improve.

The images were released after the long process of fully focusing the telescope’s mirror sections was completed. Engineers say JWST’s optical performance is “better than the most optimistic predictions,” and astronomers are on their side with excitement.

“It wasn’t break the laws of physics, Mark McGreen, ESA’s Senior Adviser for Science and Exploration and part of the JWST Science Working Group, said, on Twitter.

In their excitement, astronomers began publishing comparative images – from previous telescopes to JWST in the same field of view – demonstrating the development of the improvement in resolution.

Astronomer Andras Gaspar, working with JWST’s MIRI medium-infrared instrument, combined images from the WISE (Wide Infrared Survey Explorer) telescope into a JWST image of the same field of view, the Large Magellanic Cloud, a small satellite galaxy of[{” attribute=””>Milky Way.

How awesome is JWST/MIRI? Well, let’s compare the latest press release image to that of the WISE all-sky survey at 4.6 microns. This is the closest wavelength image I could find. Spitzer IRAC would have been better (slightly higher resolution and similar wavelength). https://t.co/EXqP57sULt

Then he realized Spitzer also has taken an image of the LMC, and then created the comparison of the three telescopes, seen in our lead image.

“To be fair, WISE with its 40 cm diameter telescope was only half the size of Spitzer’s [85cm primary] But both are very small compared to JWST [6.5 meter primary]” Gaspar said on Twitter. “That’s what you get with a large aperture! Resolution and sensitivity. MIRI gives mid-infrared! HST [Hubble Space Telescope}] I can’t get to that wavelength.”

And there is more:

Since MIRI #JWST gets so much love before and after, I thought I’d do the same with the precision-guidance sensor: this is one of its fields in the Large Magellanic Cloud as previously imaged in near-infrared by the @VISTA Survey Telescope. 1/ https://t.co/G4yfhPWTqQ

Astronomers and engineers seem amazed at how accurate JWST is. You may find this surprising. I mean don’t they test on the ground to see the capabilities of the telescopes before launching them? Yes, but ground tests don’t always tell the whole story, as does Marshall Perrin, Webb’s deputy project scientist at the Space Telescope Science Institute. He explained on Twitter.

“Yes, we tested the entire optical train in Houston’s cooling technology – but that didn’t actually tell us about the absolute performance,” he said. he wrote. “Not completely. In many ways, the test environment on the ground was challenging and different from space. “

Perrin explains how gravity plays a role, as JWST’s mirrors were designed to have a certain shape in zero gravity, but in all ground tests they were inevitably distorted by gravity, requiring digital models to compensate.

After that, there is no way to test on Earth how the telescope might operate in Zero-g, as far as stability or whether there are any vibrations from the spacecraft. And although ground testing in the vacuum thermal chamber at Johnson Space Center could match the temperatures JWST would be exposed to in space, Perrin said some impacts in the testing chamber caused optical instability.

“Performance forecasting should not be just a manual wave or desire, but should be based on quantitative numerical models and budgets including assessment of risks and uncertainties,” he wrote.

So, while predictions are useful, there are always skepticisms. For now, let’s bask in the joy and wonder what JWST actually has to offer.

The first official photos of the light are expected to come out in July.

Originally Posted in universe today.

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