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James Webb is fully deployed

nasa.gov

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Re: James Webb is fully deployed

#471

Post by SirHound »

voidfunc wrote: post #419
JohnBooty wrote: post #208

Earlier quoted context omitted.

Great blog post from NASA themselves explaining it: https://blogs.nasa.gov/webb/2022/01/06/why-doesnt-webb-have-... the post is really not very long and I would suggest getting it straight from the horse's mouth, but for those not willing to devote a click here are arguably the most relevant bits! "deployment surveillance cameras would not add significant information of value for engineering teams commanding the spac…

Once again scientists miss the entire point. It is about marketing and making people interested. It makes it easier when you go back five years later and ask for more money if people can see the multi-million dollar toy they paid for.

It’s a telescope with a camera stuck to one end. I think people will be able to see what they paid for.

Re: James Webb is fully deployed

#473

Post by bumby »

WalterBright wrote: post #304
bumby wrote: post #215

Earlier quoted context omitted.

Not every part meets the criteria to be a "critical" spare. You don't have a complete set of spares for every component.

Are you suggesting that spares are only produced for the cheap parts?

No. Only for the parts deemed critical.

An example may be a part with a long lead time and no redundancy. If it is found defective during testing, they need a replacement right away and don’t want the schedule to slip while it gets fabricated

Re: James Webb is fully deployed

#474

Post by bumby »

WalterBright wrote: post #429
kragen wrote: post #220

Earlier quoted context omitted.

A lot of times when you make one of something, there's stuff you would make tooling for if you were going to do more than one, but which instead you do by hand. Sometimes this is even true in software, but not very often, because the advantages of being able to recompile something from source code are so huge.

Even when doing things by hand, making a duplicate alongside the original is not much more time. That happens to me every time I do something by hand.

I think the error in your assumption comes, in part, that there’s is tooling set u for mass production of each part.

A lot of parts are hand-fabricated. The setup may take time but it’s not necessarily like a assembly plant that requires new dies on each design.

Re: James Webb is fully deployed

#475

Post by sailingparrot »

WalterBright wrote: post #435
sailingparrot wrote: post #355

Earlier quoted context omitted.

Your point is completely unfair. Sure if our goal was to mass manufacture a "cheap and reliable JWST" we could, with a lot of money, create an entire assembly line and benefit from economies of scale. And then what? What are we supposed to do with 100s of JWST? It's cool they only cost 200M$ each now, but we don't need them. What we need after JWST is a different telescope with different technologies to answer questi…

Is it unfair? In Spring 2020, in this forum, the vaccine experts here told me in no uncertain terms that a vaccine would take 18 months to develop. I said it could be done in 6 if all the slack was removed, and things done serially were done concurrently. I was told that was all completely unreasonable and impossible. 6 months later, the vaccine was released. The JWST has what, 390 single points of failure, and cost…

What I am saying is unfair is your insistence on trying to think of astronomy as a problem that can be resolved by scale.

> that a vaccine would take 18 months to develop. I said it could be done in 6

Cool anecdote. I was also part of those who thought it would be done earlier, we agreed on this. This is not comparable at all.

> so $10B was spent to ensure it would not fail. And it worked! But suppose for $1B one could build a less reliable JWST.

That was the plan, JWST was supposed to cost 1B$, not 10B$. And then we were supposed to start building other telescope based on the lesson learned with that design such as: https://en.wikipedia.org/wiki/Large_Ultraviolet_Optical_Infr....

But it ended costing 10B$, not because that's what anyone wanted, but because that's what happens when you try to push the enveloppe. Just like the A380 program ended up costing 25B instead of 9 planed.

> Instead, one makes redundant systems. It is far, far cheaper, and yet more reliable than going for perfection

The JWST does not have 390 single point of failures like the media like to say, a lot of those are highly preferable but not make or break: If the mirror wings failed to deploy, JWST would still work at a lower res. If some of the sunshade layers didn't deploy correctly, it would still work. If the momentum flap didn't deploy, it would still work but require more fuel to keep orbit stable, lowering life expectancy of the missions, Latching mechanisms and release bolts where all designed with tolerance for some of them to fails etc.

There are was actually just a handful of true single point of failures with no redundancy.

> But I do know how airliners are designed and built

Yes I think by now we are all aware since you keep mentioning it in every single one of your comment. And I don't doubt that you know what you are talking about when discussing airliners, but it also seems to me that your experience is a hammer and now everything you see looks like a nail to you.

What I find irritating, is that the team that build the JWST is made of many, many highly intelligent individuals that thought about about how to best respond to the need of astronomy over 25 years, and you seem to think that they are complete idiots that didn't think about solutions and problem that you can think of in 5 minutes on hacker news. They have. A lot of those people come from the world of airplanes. One the biggest contractor for the JWST is Lockheed, which knows a thing or two about designing airplanes and asssembly line.

Hubble, was actually built like that, as it's actually a repurposed KH-11 reconnaissance satellite. Lockheed built 18 of those. Only one of them was ever ordered for astronomy.

So do not worry, JWST is built like it is, not because no one thought about your ideas before, but because they don't help solve what we actually care about.

Re: James Webb is fully deployed

#476

Post by sailingparrot »

WalterBright wrote: post #390
sailingparrot wrote: post #284

Earlier quoted context omitted.

> but it can still "observe anything in the sky, and get the most detailed pictures ever seen of them". That's my point: it cannot! Not all objects are visible at all wavelengths. Some extremely old and far-away objects are not emitting anything in the shortest wavelengths because of red-shifting, and you need infrared capabilities to see them (hence JWST). Dust clouds are also blocking certain frequencies of light f…

Are you seriously suggesting there is no other value in infrared light images? That there's only one thing worth looking at in infrared? That nothing else one points it at could possibly yield a surprise? I'm astonished. I don't think we remotely know enough about the universe to draw such conclusions.

> Are you seriously suggesting there is no other value in infrared light images

I have never suggested that no. What I am suggesting, is that if you asked the astronomy community wether they want to spend 3-5B$ into getting an exact copy of the JWST, or spend those 3-5B$ into a different telescope, with capabilities complimentary with the JWST, you would get an absolute overwhelming majority voting for the latter.

We are still going to invest in future IR telescopes, but they won't be exact copy of JWST, they will either be complementary (see the future Roman space telescope) or will just be based on newer technologies and be more powerful.

There is simply little value in getting twice the same instrument for that price tag.

Why didn't we build another Hubble? The US build 18 of those for reconnaissance purpose but a single one for astronomy. Because the astronomy community never chose to spend their budget on that, instead they chose 4 new telescopes, with 4 different capabilities, all different from Hubble. That's where JWST comes from. They could have asked for 4 JWSTs instead, but they didn't because that would be terribly pointless.

Re: James Webb is fully deployed

#477

Post by philistine »

dev_tty01 wrote: post #394
JohnBooty wrote: post #349

Earlier quoted context omitted.

I just want to make sure I understand. Your position is that they should have added significant complexity to a maneuver that was already the most complex of its kind. A maneuver with $10 billion and two decades of work on the line. In order to make the first 30 days of a 10+ year mission marginally more entertaining. You propose this while fully aware that the "entertainment" in question consists of things unfolding…

NASA has often added video or image capability with low scientific value to increase public engagement, despite the associated risk and cost. They made a call not to do it this time. My only point is that it would have been a nice PR opportunity if they could have found a way to make it work within their mission parameters. I apologize if making such a simple and obvious point has offended you in some way.

Nope. In the category of probes/satellites, NASA doesn't put cameras that aren't needed. Probes on Mars get cameras, but that's because they're in a dynamic environment. They then use those cameras in fun, engaging ways.

Re: James Webb is fully deployed

#478

Post by BurningFrog »

sailingparrot wrote: post #284
BurningFrog wrote: post #264

Earlier quoted context omitted.

You seem to argue against something I didn't say. I understand it observes a different frequency range than Hubble, but it can still "observe anything in the sky, and get the most detailed pictures ever seen of them".

> but it can still "observe anything in the sky, and get the most detailed pictures ever seen of them". That's my point: it cannot! Not all objects are visible at all wavelengths. Some extremely old and far-away objects are not emitting anything in the shortest wavelengths because of red-shifting, and you need infrared capabilities to see them (hence JWST). Dust clouds are also blocking certain frequencies of light f…

> > but it can still "observe anything in the sky, and get the most detailed pictures ever seen of them".

> That's my point: it cannot! > > Not all objects are visible at all wavelengths.

A JWST observation showing nothing is new science. Now we know that object emits no light at those wavelengths even when observed by the most sensitive instrument!

But of course those are exceptions. Most things we point JWST to will be seen in greater detail than ever before, and also in frequencies not seen before.

> If you care about observing very energetic objects like neutron star, you need x-ray capabilities. > > If you care about studying atmosphere of exoplanet your best bet is UV light, and this is why NASA is working on LUVOIR.

This feels like deliberate misunderstandings (conscious or not) of my points. I don't think we can get any further in this discussion.

Re: James Webb is fully deployed

#479

Post by bmitc »

DSMan195276 wrote: post #447
bmitc wrote: post #418

Earlier quoted context omitted.

Who said anything about generating infrared light? And I don't know what your last sentence is in reference to. Yes, it needs to cool down. Why is that relevant to this discussion other than what's already mentioned about that being a downside to operating cameras? From the article so people can just debate NASA's own reporting: > Although infrared or thermal-imaging cameras on the cold side could obviate the need fo…

I think that article is leaving out some of the other problems (which is understandable, it already covers plenty of downsides). The whole point of keeping the cold side cold is so that it doesn't emit any IR radiation (otherwise the JWST couldn't work). So by design it's "dark" to an IR or thermal camera in the same way it's dark to a visible light camera. Certainly you can build a camera to see it anyway (without e…

That makes sense. Thanks. It was a question of mine just how much IR would be there to see.

Re: James Webb is fully deployed

#480

Post by bmitc »

ilstormcloud wrote: post #444
bmitc wrote: post #418

Earlier quoted context omitted.

Who said anything about generating infrared light? And I don't know what your last sentence is in reference to. Yes, it needs to cool down. Why is that relevant to this discussion other than what's already mentioned about that being a downside to operating cameras? From the article so people can just debate NASA's own reporting: > Although infrared or thermal-imaging cameras on the cold side could obviate the need fo…

The JWST has an extremely sensitive IR camera. And it is going to cool down to near absolute zero so that the IR sensors don't get flooded with radiation from the rest of the telescope. Because it will get so cold, it is not going to be emitting much IR (I think this is what the GP said when they said "generating"). Your typical deployment observation IR camera's won't be of much help in that case.

That makes sense, and I got thrown off (by maybe misreading the comment) thinking they meant the camera or something else would generate additional IR to illuminate the telescope, which I got confused by. It makes sense now that the comment was meaning that the cool down was to reduce as much telescope generated IR noise as possible.
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