There's a Problem with Webb's MIRI Instrument 

You're human. We love your work! That's all there is to it. ❤️😎

Well, I was just about to mention that!

Not everywhere though, so no big deal ;)

Could have blamed the cat.

It's good to know a bit of greek (and latin) when you work with science. It's the same "chromos" as in "monochrome", "chromosphere" and... Chrome. Di-chroic - double-coloured.

I forgot about that! There's been some big ones recently, too. I'll have to check if they went L2's way...

Yeah, I was also thinking about the issues some mission's reaction wheels had. But, its so early in JWST's lifetime.

nah, when china manufacturers opened back up, everyone and their dogs got defective junk

@@MrPaxio looool. You can get good parts from china and bad parts from china. What your referring to is the lack of quality control. This isn't a Chinese specific issue my man. Not sure how everyone can quite grasp that. And recently supply in a lot of industries is outpaced by demand so there's more pressure to do less rigorous QC to try and produce enough to make demand.

Check out the company ASML which makes the advanced lithography instruments in the world based in the Netherlands. Now they are doing ultraviolet lithography. The do the same complex rerouting of light in their instruments.

I'll give it a shot - but I will ignore the very large number of flat mirrors which are used to fold a very long optical path (which gives high magnification and fine detail) into a compact instrument. 0:31 The input beam from the telescope is fed into the MIRI instrument and most of it is directed into the imager. 0:36 A group of curved and flat mirrors changes the f/number of the beam from the telescope to match the requirements of the medium-resolution spectrograph (MRS). 0:38 A tilted flat mirror diverts the beam into the spectrograph. A small image of the primary mirror is formed on the flat mirror (eighteen hexagons and one missing in the middle). Where the missing hexagon would be there is a hole and this is used (as needed) to introduce a uniform light through the entire spectrograph for calibration. Rather than keep switching the calibration light on and off (which would eventually burn out the filament) it is kept running and a tilting mirror directs the beam through the hole. This is one of only three mechanisms in the MRS. When the calibration light is not needed it is directed into one of the many light traps in the MRS. They are not all shown in this animation - it's already cluttered enough ... 0:40 The incoming light is split into four channels by wavelength. Sets of three filters reflect selectively longer wavelengths. The filters are carried on two rotatable drums which allow different parts of the wavelength range to be examined. Three consecutive observations are needed to cover the whole wavelength range. 0:48 An image of the sky (in a specific wavelength range) is produced on the image slicing mirror. This is a crucial feature of the MRS - it slices the image of the sky into short strips and then 0:51 projects them as a single long strip which is equivalent to the slit at the entrance of a conventional spectrograph. In this way, a larger object ( a nebula, say ) can be analysed in a single observation and best use is made both of detector real estate and available observing time. 0:57 The four channels of sliced, stacked light are then re-imaged (again as the image on the primary mirror) onto diffraction gratings which spread out the light to form a spectrum. The diffraction grating is a flat mirror which has very fine grooves cut into it - it acts in much the same way as the pits in a CD can form a spectrum. The gratings are mounted on the underside of double-ended motors which also rotate the dichroic barrels. In this way, the dichroics and gratings can never get out of synch with each other. 1:06 For each channel, a set of three curved mirrors then produces an image of the spectrum on the detector array. There are only two detectors so the images from two channels are aligned side by side on a single detector array. The detectors are 1024 x 1024 arrays of Arsenic-doped Silicon pixels, each of which is 25 micrometres square.

Not near as complicated but just look at a modern camera lens, I'm an amateur Wildlife Photographer and when I see a blueprint of some of my lenses it makes me wonder how they focus correctly much less last for many years..Some of them will have 20+ elements ( groups of glass ) in them that all have a specific job like correcting for sharpness and chromatic aberrations etc etc...And like I said earlier they do it flawlessly for years in sub zero conditions to extreme heat and humidity.. Humans have made some amazing things. It's a shame we can't figure out how to keep from putting bullets in each other to resolve a conflict...And I'm not anti gun by no means I'm referring to war

Thanks!

Thank you kindly!

He was mad I put him on camera, but he was walking on my keyboard!

Glad it helped!

110% w/ ya!

Totally disagree. I want my money back.

Here’s hoping!

Life is terminal and in the future all of Webbs knowledge will be lost to the sands of time.

@@suspicionofdeceit that's a very eloquent way to put it, but what I meant was that I hope it's not going down so soon

@@suspicionofdeceit Aren't you just a ray of sunshine.

@W Never going to happen

@@ElderberryThee3rd But he is right tho.

Good news then. This shouldn't affect MIRI's imaging at all. This affects only mid-resolution spectroscopy. That would be a significant loss of scientific data, but the pretty pictures will continue unimpeded.

@@mal2ksc A picture is worth a thousand words but a spectrum is worth a thousand pictures. Actually it's 1024 - but who's counting.

I’m sure they thought about it a lot but remember everything costs weight and that reduces possible performance elsewhere. It might not be at all practical to make it “repairable” remotely

@@mduckernz -- I was not pushing the remote-repair as the issue, the issue is we don't have a way to send people to repair or upgrade it, so if anything happens that we can't repair remotely then we are stuck and could end up with a 10 billion dollar rock.

With starship launch capability, a reasonable cost unmanned repair/upgrade mission to JWST will be possible in 2 or 3 years.

Unfortunately, JWST lacks the provisions for being serviced in space. Hubble has handles and easily accessible fasteners to make the job a lot more practical. I use the present tense because it's still technically possible to perform more servicing missions on Hubble, so long as a vehicle exists to get there -- like Starship, perhaps. And since we don't have another comparable optical band telescope in orbit, we really should be looking to keep Hubble going as long as possible. In other words, it won't work for Webb, but it might still work for another Hubble service.

@@MrPaxio why bother typing ?

Keep in mind that only the spectroscopy instrument in MIRI is the issue not the imaging instrument. Also the team has a process for addressing technical issues that arise just as Hubble did. And Hubble often had issues resolved remotely.

Same here. So far, all we have is the press release plus the already available information. I'm sure they'll reveal more info as they learn it though.

From some time I generally became curious about bearings used in space. Things like lubricants would need to work in those temperatures and vacuum (so not sure if they are even used that much).

@@ImieNazwiskoOK Yea agreed, I wouldn't be surprised if there aren't any lubricants. I would imagine there could be specialized sputtered coatings or surface treatments instead. The extreme high and low temperatures, vibrations during launch - I couldn't imagine any kind of lubricant staying in place... they'd probably find their way all over the shop.

Yes.

@@LaunchPadAstronomy Thanks

Almost certainly there will be at least one flight-spec motor/rotor assembly and probably more than one.

Yup it's important and mechanical stuff tends to be hard to fix when it's 1,000,000 miles away. Hopefully it's just a setting that needs an adjustment and not a mechanical problem.

He specifically says it needs to be split for spectroscopy and the packaging is actually as compact, lightweight, and least complex that it could be. When you have a telescope that needs different sensors and mechanism to do different types of science and the only light input for all the instrument is the secondary mirror, there has to be a way to split that light up for the needs of the differing instrumentation. Otherwise you’d be building 4 or more telescopes to do the job of one. He even breaks down the main science that the telescope is used for In this video. Want to know more? Go watch other videos on his channel he explains how everything works and why. Physics isn’t easy, at least not on the level Webb is performing. If you’re interested check it out seriously. It’s not like they found just send a big space telescope with a single Sony cmos sensor in it and call it a day.

NIRCam is fully redundant, with an A and B side.

There is always a tradeoff to adding more complexity to an already complex piece of technology. And besides that your question may be premature as this issue only just happened so the team has hardly begun to problem address the matter. Hubble had problems arise as we which were often dealt with remotely. Learn some patience. I hear that is a virtue!!

The space available is very small; the triangular dichroic wheel is only 65mm across flats. This precludes the use of a bearing which has an inner race, one set of balls, an intermediate race (grooved on both the inner and outer surfaces), a second set of balls (with more balls) and an outer race.

high dynamic range

Love it!

2:20

He's a good guy, but he thinks he's a lion. Suffice to say, he doesn't like it when "Samson and Delilah" comes up.

And if it's not a fixable problem, I expect they'll figure out the most useful setting to get stuck in and leave it there -- better to have the instrument stuck on one known setting than to have it get stuck with things misaligned so it can't be used at all.

feel free to design (and build) one

Losing MRS capability on MIRI would be really bad indeed but I'm just gonna wait and see what the resolution is going to be.

I hope you get your spacebar fixed, buddy