James Webb Space Telescope - the ultimate

Who's going to try and image it?
Curious to know its change in brightness once the shields start deploying.
https://unistellaroptics.com/ephemeris/

Well deserved apod dedicated to the JWST today 
Let's keep fingers crossed that everything will go well in the upcoming stages of its way to L2.

Sean van Drogen:
Only another 6 months or so before it starts collecting its first data. Can’t wait to see the first results

I heard of it but didn't know the reason of such a term. Here is a good arcticle I've found on this topic 
https://www.planetary.org/articles/jwst-first-images

I wonder if it is possible to find it with the scope now?

Cool website, Where is Webb?, from NASA that tracks how far Webb is and it's various deployments

https://www.jwst.nasa.gov/content/webbLaunch/whereIsWebb.html

What a relief the launch went so well!  

I spent many years working on JWST in different capacities.  Early in the program, I sat on the optical test review committee for a while.  One of our first jobs was to evaluate the two proposals made by the vendor groups who were vying to build the telescope.  These proposals were huge and they incorporated a thousand technical graphs and charts.   A key argument centered around how to meet a requirement to optically test the telescope at low temperature (50 K as I recall) in a vacuum.  It turned out that finding a vacuum chamber large enough to hold this telescope was a serious challenge.  Vendor A had access to a vertical test chamber and the other vendor had found a horizontal test chamber.  So vender A came in and gave a complicated technical presentation showing that the only way to test the telescope was by offloading gravity in a vertical test chamber.  They had a large number of charts, calculations, and measurements showing that the test was not possible with a horizontal chamber.  The next day, vendor B came in and demonstrated through calculations, charts, and measurements that the ONLY way to successfully test the telescope was to measure it horizontally!  They showed conclusively that a vertical test tower would not work.  Behind the scenes, we were all left scratching our heads!  Both groups had very effectively proven that the other group's method would not work–so which is it?  The calculations and data were all so complicated that no one could easily shoot down either argument.  So it will be interesting to see how well the telescope works when it gets on orbit.  As I recall, the telescope was tested horizontally.

I also ran a company called 4D Technology that supplied all of the optical metrology test equipment for the program.  Our Phasecam interferometers were used to test all of the optical components and I was lucky to install one of them at Tinsley where the primary mirrors were figured.  I remember standing next to one of the hexagonal primary mirrors on the polishing machine while it was being figured.  Since beryllium is so toxic, the machine was tented and we all had to wear gloves, clean suits, and masks.  I might have even set up the interferometer on another segment, but it may have been a dummy.  I don't recall.

We also made the multi-wavelength interferometer for testing the phasing process on the primaries.  Remember that all of those hexagonal mirrors don't just have be geometrically aligned.  They have to be adjusted in piston to have less than a quarter of a wave step between the wavefronts reflected from each mirror segment.  This is a very tricky thing to do so there were a lot of optics folks developing algorithms for doing the alignment and for evaluating the results.  In hindsight, this would have been a relatively simple job using AI but to my knowledge, that's not how it was done.  I think that it uses some sort of Kalman-filter to recursively align the mirrors.  Anyway our multi-wave Phasecam could measure how well the aligned primary mirror was phased during testing.

We also supplied a 100+ Mega-Watt speckle interferometer for evaluating the carbon-fiber backplane structure.  The backplane was large, it was flat black, and it was sparse, which is why the interferometer required so much power.  It used a 1 ns pulsed laser that only had a coherence length of 1 foot so it incorporated fiber path matching loops in the reference arm to get a signal back from the structure.  That interferometer had so much power that it was a little scary when we ran it.  We had to be VERY careful with our laser safety protocols.  Charlie Precourt who used to be the chief pilot/astronaut for the Space Shuttle told me that he managed the group at Northrup that made the backplane structure.  They used the speckle interferometer to look for defects in the structure and to characterize its thermal performance.

At the SPIE meeting last summer, Ritva Keski-Kuha, who is the JWST deputy telescope manager for NASA, told me that without 4D Technology, JWST would not have been possible. We had some VERY smart engineers working on all that stuff and I was very proud to hear that all of our hard work was so important to the program.  Some of those projects were really challenging and our guys did an amazing job delivering state-of-the-art metrology capability.

I can't wait to see the first images!

John

Jonh, your insights are so exciting to read! Thanks for sharing.
I have a hope, that JWST is definitely going to tell us something about Universe that we didn't know before.

OK, it looks like NASA have given themselves a day off after the stressful deployment of the side booms and the pulling out of the sun shield.  Looking at their site, things are starting to cool down nicely on the dark side (already down to -183 C, but some way to go.  Tomorrow (Sunday) and Monday are set up for the separation of the sunshield layers and the tensioning.  Fingers crossed (yet again).

I'm a bit worried about the deviation from the planned timeline. Layer tensioning should have started already.To me this is a sign that something doesn't (didn't ?) work out as intended and that there are (were ?) some unplanned difficulties to overcome. I don't think they give themselves a day off, would be very unusual and hard to justify in such an important project. Let's hope for the best.

Hi Kuechlew,

everything is fine. Here are some more information https://blogs.nasa.gov/webb/2021/12/31/first-of-two-sunshield-mid-booms-deploys/

Resp full blog: https://blogs.nasa.gov

CS
Rüdiger

OK, they've decided to spend today characterising the operational behaviour of JWST's power systems and monitoring the temperature of various deployment motors.  So, no sunshield tensioning today.  We all need to wait another 24 hours.

Andy,

Thanks for starting this thread, I've been waiting for the JWST to go up for a while, this is very exciting! I'm really looking forward to seeing some of its first images, especially the earliest galaxies and stars.

John,

That's a great picture, thanks for sharing! I had no idea you were a contributor to this magnificent telescope.

-Jeff

Indeed, I'm very relieved. In their teleconference they revealed that they had some challenges to overcome related to the temperature of the motors involved. The project manager pointed out that the sunshield deployment is one of the most critical steps in the overall procedure and once they managed to achieve it they will have passed about 75% of the 344 single points of failure. They seem to progress well, at the time of writing they have deployed the three layers closest to the sun with two to go. On a side note: with 344 single points of failure, assuming a 99.99% probability to mitigate each single point of failure you still end up with only 96.6% success rate (assuming independent probabilities). Making this project a success is an awesome achievement.

It looks like the "Where is Web" website is not updated properly. Temperature is still about the same as the days before but with 3 sunshields deployed there should already occur a quite significant change.