The James Webb Space Telescope and stuff

[Shpaget]

The engineering of the mirror actuators is genius. Coarse and fine adjustment using the same motor, getting 21 mm of travel while still being capable of 8 nanometer resolution. It's just crazy.

 

[Elthy]

Cant watch the video right now, but this looks very interessting.

[JoeSchmuckatelli]

7 hours ago, Shpaget said:

The engineering of the mirror actuators is genius.

That is a cool vid - thanks!

 

In other news, First Light:

Quote

This week, the three-month process of aligning the telescope began – and over the last day, Webb team members saw the first photons of starlight that traveled through the entire telescope and were detected by the Near Infrared Camera (NIRCam) instrument. This milestone marks the first of many steps to capture images that are at first unfocused and use them to slowly fine-tune the telescope. This is the very beginning of the process, but so far the initial results match expectations and simulations.

...

The images taken by Webb during this period will not be “pretty” images like the new views of the universe Webb will unveil later this summer. They strictly serve the purpose of preparing the telescope for science.

The Blog has WAY more info on what they're doing and the process than most people are interested in - but for those who are, take a look: James Webb Space Telescope (nasa.gov)

Edited February 9, 2022 by JoeSchmuckatelli

[StrandedonEarth]

 

[VaPaL]

 

https://blogs.nasa.gov/webb/2022/02/11/photons-received-webb-sees-its-first-star-18-times/

Edited February 11, 2022 by VaPaL

[JoeSchmuckatelli]

Webb took a Selfie!

(Time stamped)

NINJA'd!

[HebaruSan]

The dots have been arranged to mirror the panels while the team works on each segment's individual alignment:

https://phys.org/news/2022-02-webb-team-dots-starlight-hexagonal.html

Edited February 19, 2022 by HebaruSan

[HebaruSan]

The mirrors have been aligned:

And stacked:

https://blogs.nasa.gov/webb/2022/02/25/webb-mirror-alignment-continues-successfully/

[Minmus Taster]

51 minutes ago, HebaruSan said:

The mirrors have been aligned:

And stacked:

https://blogs.nasa.gov/webb/2022/02/25/webb-mirror-alignment-continues-successfully/

Great news! so.. who's gonna get to post the "It's working!" GIF when this baby starts doing science? 

[Shpaget]

In the stacked image, the gaps in "lens flare" - are caused by wave interference, right? Is it because the mirrors are still slightly misaligned vertically making some light paths longer than others?

[HebaruSan]

4 hours ago, Shpaget said:

In the stacked image, the gaps in "lens flare" - are caused by wave interference, right? Is it because the mirrors are still slightly misaligned vertically making some light paths longer than others?

That seems to me like a plausible interpretation of the current status and remaining work, but I don't know enough about optics to say whether it's responsible for that specific visual artifact:

Quote

Although Image Stacking put all the light from a star in one place on NIRCam’s detector, the mirror segments are still acting as 18 small telescopes rather than one big one. The segments now need to be lined up to each other with an accuracy smaller than the wavelength of the light.

The team is now starting the fourth phase of mirror alignment, known as Coarse Phasing, where NIRCam is used to capture light spectra from 20 separate pairings of mirror segments. This helps the team identify and correct vertical displacement between the mirror segments, or small differences in their heights. This will make the single dot of starlight progressively sharper and more focused in the coming weeks.

[JoeSchmuckatelli]

Quote

This week the Webb team continued to make progress in aligning the telescope to the NIRCam instrument. Between taking the data to understand the optical components, we continue to check out the science instruments. The NIRSpec instrument includes a microshutter array of a quarter-million miniature movable windows, each 0.1 by 0.2 millimeters in size. The microshutter array allows scientists to target specific galaxies in fields they are studying, while closing the windows on the background or other objects which would contaminate the spectra. We have begun testing the mechanism and electronics that control and actuate the microshutters.

 

 

James Webb Space Telescope (nasa.gov)

 

For those of us hoping, in effect, for a 'Hubble 2.0' (lots of pretty pictures along with cool science) it seems Webb's main goal is looking at the early universe & trying to find first generation stars:

 

Quote

 

“One way to confirm whether we are finding the first stars is to accurately measure metallicities of very distant galaxies. The astronomical term, metallicity, is a measurement of the amount of material heavier than hydrogen and helium – so a low metallicity galaxy would indicate it was made up of these ‘First Stars.’ One of the most distant galaxies discovered so far, known as MACS1149-JD1, is confirmed to be at redshift 9.1 and emitted the light we see when the universe was only 600 million years old. The light from this distant galaxy has been traveling ever since then and is just reaching us now.

“In the first year of Webb science, I have an observing program to study this galaxy and determine its metallicity. I will do this by attempting to measure the ratio in the strength of two spectroscopic lines emitted by oxygen ions, originally emitted at violet-blue and blue-green visible light (rest frame wavelengths at 4,363 angstroms and 5,007 angstroms). Thanks to cosmological redshift, these lines are now detectable at the infrared wavelengths that Webb can see. The use of a ratio of two lines of the same ion can provide an exquisite measurement of the gas temperature in this galaxy and, through relatively simple theoretical modeling, will provide a robust measurement of its metallicity.

“The challenge is that one of these lines is usually extremely weak. However, this line tends to get stronger at lower metallicity. So if we failed to detect the line and measure metallicity for MACS1149-JD1, that would likely mean that it has already been enriched by the heavier elements, and we need to look further and harder. Whether using my data or with future programs, I fully expect that during its operational lifetime Webb will be able to find objects with metallicity sufficiently low to hold keys for understanding the first generation of stars.”

–Massimo Stiavelli, Webb Mission Office head, Space Telescope Science Institute

 

 

[Spaceception]

This looks really good https://www.nasa.gov/press-release/nasa-s-webb-reaches-alignment-milestone-optics-working-successfully

Edited March 16, 2022 by Spaceception
Ha, ninja'd

[Minmus Taster]

[HebaruSan]

Some more details on how this step was done. "We have exceeded every expectation. The telescope has performed better than the models said it should."

[JoeSchmuckatelli]

1 hour ago, HebaruSan said:

Some more details on how this step was done. "We have exceeded every expectation. The telescope has performed better than the models said it should."

The sheer enthusiasm is awesome!  They must be quite pleased.  (So much better than a quibbling 'uh-oh'!)

[Just Jim]

And I thought I got excited... lol
 

 

Edited March 16, 2022 by Just Jim

[HebaruSan]

They've added interactive graphs of the temperatures of the various components during the cooldown phase:

https://jwst.nasa.gov/content/webbLaunch/whereIsWebb.html (click "Temperature Plots")

[Gargamel]

I don't think I saw this in thread before:

 

[Gargamel]

A candidate star that is possibly 12.9 billion LY away has been identified, and is now on the schedule for the first round of observations by the JWST.

[HebaruSan]

The cryo-cooler has gotten Miri pretty close to its target temperature. I'm guessing that they've gone back to passive cooling for the last few degrees, since it's going more slowly again now (but I haven't seen any official announcement along those lines):

[NFUN]

9 minutes ago, HebaruSan said:

The cryo-cooler has gotten Miri pretty close to its target temperature. I'm guessing that they've gone back to passive cooling for the last few degrees, since it's going more slowly again now (but I haven't seen any official announcement along those lines):

They can't passively cool that low, which is why they have the cooler in the first place. At a certain point they're turning off the heaters they were using to prevent ice from forming as it cools, so they've probably turned off the heaters and turned down the cooling power to compensate 

[NFUN]

or they just decided to yeet it to below 7 lmao

 

explanation for the plateau: https://blogs.nasa.gov/webb/2022/04/06/webbs-mid-infrared-instrument-cooldown-continues/

Edited April 8, 2022 by NFUN

[HebaruSan]

5 minutes ago, NFUN said:

or they just decided to yeet it to below 7 lmao

Heh, now I'm imagining that the operator of the cryo-cooler saw my post, swore, and turned it back on.   

[JoeSchmuckatelli]

If you want to get a feel for just how ridiculously insane Webb is - read this:

Quote

 

At cryogenic temperatures, beryllium has a long thermal time constant, which means that it takes a long time to cool or to heat up. The primary mirror segments are still cooling, very slowly.

The secondary mirror, hanging out on the end of its support structure a long way from any heat sources, is the coldest mirror, currently at 29.4 kelvins. The 18 primary mirror segments range in temperature from 34.4 kelvins to 54.5 kelvins. An advantage of beryllium mirrors is that they don’t change shape with temperature the way glass mirrors would at these temperatures, so the temperature range does not affect the telescope alignment process.

Currently, four of the 18 mirror segments are above 50 kelvins: at 52.6, 54.2, 54.4, and 54.5. These four mirror segments emit some mid-infrared light that reaches the MIRI detectors. Since all the mirror temperatures are now below 55 kelvins, it is expected that MIRI will be sensitive enough to perform its planned science, but any additional cooling of these mirrors will only enhance its performance. The Webb team hopes to see the mirrors cool by an additional 0.5 to 2 kelvins.

...

Later in commissioning, we plan to test the thermal dependence of the mirrors on the attitude. We will point Webb at a hot attitude for several days, and point Webb at a cold attitude for several days, in a process called the thermal slew. This will inform us how long it takes for the mirrors to cool down or heat up when the observatory is at these positions for any given amount of time.

 

"Is Webb at its final temperature? The answer is: almost!"

James Webb Space Telescope (nasa.gov)