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James Webb is fully deployed

nasa.gov

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Re: James Webb is fully deployed

#391

Post by mlyle »

WalterBright wrote: post #301
mlyle wrote: post #162

Earlier quoted context omitted.

> Assuming your figures are correct, you'll get double the data for another 30% cost. I think 30% is probably a reasonable guess, based on past programs where people have flown 2. You get to reuse design and some fixturing. You get to share some operational costs. But you're not at unit counts where you benefit from mass production techniques and a whole lot of verification and qualification work are still effectivel…

Another poster here remarked that spares would be made. That would indicate the cost of doing so isn't that remarkable.

Lots of engineering models. Some spare parts for parts of assemblies.

Not a lot of complete, flight-capable assemblies.

I'm actually teaching a bunch of high school students to make a cubesat right now, and we are going through costing of:

* Prototypes -> protoflight -> flight, no engineering model

* "Flatsat" electronic engineering model, prototypes -> protoflight -> flight

* Prototypes -> qualification article -> flight article, + "flatsat"

* Prototypes -> qualification article -> flight article + ground engineering model

There's a whole lot of derisk that happens as you go down that list, but the cost and labor increase (the latter is "free" for us but also limited) is substantial.

Re: James Webb is fully deployed

#392

Post by ddalex »

mturmon wrote: post #358
freeflight wrote: post #346

Earlier quoted context omitted.

> the telescope is aimed at the dark and away from the sun To be more specific; It's "parked" in an orbit [0] that constantly puts Earth between the sun and James Webb. So it's not only aimed away from the sun, Earth is also acting as a planetary scale sunscreen for it. [0] https://en.wikipedia.org/wiki/Lagrange_point

JW does indeed circle that Lagrange point, but it is definitely not in Earth’s shadow. The JW orbit semi major axis (about the L2 point) is order of 500,000 km. The radius of Earth is about 6500 km. Thus, the shadow of the Earth is extremely small compared with the excursions of JW.

The earth's shadow never reaches L2 anyhow - it's only penumbra at that distance since the angular size of the earth is smaller then the angular size of the Sun

Re: James Webb is fully deployed

#393

Post by WalterBright »

sailingparrot wrote: post #254
godelski wrote: post #213

Earlier quoted context omitted.

Instead of comparing to other telescope projects maybe better to compare to other mega science projects. Or better yet, other government costs. Though of course we'd need to run a cost benefit analysis. The thing is that these numbers are big for us and most companies, but these are government numbers and decades of work. Both factors are important. It's $11bn over 24 years, or 458m/yr. I'm happy to pay an extra $3/y…

> I'm happy to pay an extra $3/yr for this project. Yes, I think many of us would be happy to. But the reality is that NASA has to fight a pretty ferocious budget battle every year, and often (not always) delay and increase in JWST cost has meant postponing or cancelling other missions. For example the Nancy Grace Roman Space Telescope, which was deemed the top priority by the decadal survey in 2010 almost got cancel…

If it makes you feel any better, if I had Gates' money I'd be funding a fleet of probes. Most of the same design :-)

Perhaps the cost of NASA probes is so high because politically they cannot tolerate failure. This drives the cost up 10x, which means it's a self-fulfilling prophecy that failure is career-ending.

Contrast this with Musk's approach to blow them up until they work, and then he has cheap launch vehicles.

Re: James Webb is fully deployed

#394

Post by dev_tty01 »

JohnBooty wrote: post #349
dev_tty01 wrote: post #345

Earlier quoted context omitted.

Yes, I get all of that, but they still missed an excellent PR opportunity. NASA really could have built some engagement showing images of the deployment process, even if the images wouldn't have direct scientific benefit. Good PR leads to improved funding which leads to more science.

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.

Re: James Webb is fully deployed

#395

Post by mlyle »

WalterBright wrote: post #206
lisper wrote: post #187

Earlier quoted context omitted.

That's not true. The potential for surprises gets smaller and smaller the more data you collect. The Webb will produce surprises at first because it is able to make new kinds of observations that were not possible before, but after a while that new data will be used to improve our models and subsequent observations in the same regime will (almost certainly) be less surprising as a result.

> The potential for surprises gets smaller and smaller the more data you collect. Mathematically, you are quite correct. But do you really believe that with one little ole' telescope pointed at the freakin' universe you're going to reach a significant point of diminishing returns? It's like saying if you invent the first microscope, and discover bacteria, why bother with another one?

> But do you really believe that with one little ole' telescope pointed at the freakin' universe you're going to reach a significant point of diminishing returns?

I believe that James Webb has some unique capabilities, and a whole lot of overlap with other instruments, too. For things that you can only do in infrared, we have Herschel's history of observations, and VISTA. Sure, JWST is bigger and up at L2, and will be better overall, but VISTA's instruments have some advantages.

Not to mention all the other telescopes and ways we have of studying the universe.

There's all kinds of other things the government has spent $3B on in the intervening development time that I'd trade for another JWST. But it's a bit moot, here: NASA didn't have another $3B to spend. If you made JWST $3B more expensive, you'd not get 2 telescopes instead of 1: you'd get 0, because JWST almost died because of cost overruns.

(And even if NASA had $3B more--- there's a lot of other things that might have been better to do with it than JWSTx2).

Re: James Webb is fully deployed

#396

Post by dragonsky »

dmead wrote: post #354
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…

Literally every other nasa mission is filmed like this now. 10 billion and we can't even get visual confirmation it's doing well. And yes. Hubble being deployed was a big deal.

I'm wondering if there is a correlation between the level of bowing to media hype by including cameras and the actual scientific value of the mission?

The recent filming of EDL of the Perseverance rover was spectacular, but a significant aim of that mission and indeed most of the recent mars rovers has been to inspire an interest in exploration and science in the public, a significant part of that is getting happy snaps of events as they happen. The pictures taken were also of significant interest to the engineers involved as they showed events that were extremely dynamic, video being one of the best methods to gain information about the events without impacting the operation.

Web is more aimed at direct science, the products of which will, as happened with Hubble be used to make pretty pictures, which in themselves have limited scientific value, but are of enormous value in engaging the public. This combined with the difficulty and risk of capturing meaningful images given the environment makes live video a non starter.

Re: James Webb is fully deployed

#397

Post by nullc »

dTal wrote: post #324
Sebb767 wrote: post #322

Earlier quoted context omitted.

We're talking about "see the faintest light from stars millions of lightyears away"-dark (for that reason you also can't shine a light on it), with our sun in the background. To see something on that side, you'd basically need the vision capabilities the telescope itself has and that's obviously not going to happen.

It obviously needs a selfie mirror.

It has a selfie 'lens': NIRcam has extra optics that can be swung in that allows the camera to focus on the primary mirror instead of out in the great infinity.

So in this sense webb is already a camera which can photograph itself!

This capability exists for mirror alignment: They'll point webb at an isolated star, switch to focusing on the primary mirror, swap in optics that cause small phase differences to result in diffraction patterns, and then they can use the resulting images to fine tune the positioning of the mirror segments to a small fraction of the wavelength of light that they're using.

Re: James Webb is fully deployed

#398

Post by causi »

I can't help but be a little sad. JWST will be an incredible tool for scientific discovery, but its sensitivity range means it will never produce the kind of compelling imagery that Hubble did. Those pictures played a role in inspiring many of the people in the field today.

Re: James Webb is fully deployed

#399

Post by russellbeattie »

willis936 wrote: post #350
freeflight wrote: post #346

Earlier quoted context omitted.

> the telescope is aimed at the dark and away from the sun To be more specific; It's "parked" in an orbit [0] that constantly puts Earth between the sun and James Webb. So it's not only aimed away from the sun, Earth is also acting as a planetary scale sunscreen for it. [0] https://en.wikipedia.org/wiki/Lagrange_point

Actually JWST orbits around L2 at appreciable altitude. The unique aspect of the orbit is that it is never in the shadow of the Earth or moon. It guarantees consistent solar power and thermal load. https://jwst-docs.stsci.edu/jwst-observatory-characteristics...

That explains the animation! I just thought NASA was just adding some more realism into the orbit animation by adding what looked like a wobble. Derp.

Re: James Webb is fully deployed

#400

Post by cycomanic »

causi wrote: post #398

I can't help but be a little sad. JWST will be an incredible tool for scientific discovery, but its sensitivity range means it will never produce the kind of compelling imagery that Hubble did. Those pictures played a role in inspiring many of the people in the field today.

I would not be so sure about that. Many (most) astronomy photos are false color photos from quite different wavelength regions (often several different overlayed ones). So I do expect some fascinating images to come out of jwb as well.
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