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The James Webb Space Telescope and stuff


Streetwind
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http://www.space.com/34593-james-webb-space-telescope-complete-2018-launch.html

The largest space telescope ever built is... well, built. It's done. Everything is in place. There's going to be some final assembly work on the spacecraft later-on, but the telescope itself is complete and working! It's now going to be put through rigorous testing (they want to avoid the problems they had with Hubble) before being prepared for its 2018 launch abord an Ariane 5 ECA.

It was twenty years in the making. Whole new technologies had to be invented just to build it. It will be the most expensive single payload ever shot into space in the history of mankind, and it will be able to peer into space with 100 times the resolution of Hubble. I'm incredibly excited about this thing :)

Edited by Streetwind
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  • 1 year later...

Forgive the necro, but I figured it was better to continue this thread rather than start a new one, as most of the contributors to this thread are still active on the forum:

Seems they have now moved JWST (the combined optics and science instruments, anyway) to Northrop Grumman in LA, as of a week ago.

 

Edited by PakledHostage
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1 hour ago, NSEP said:

So why do they have to launch it in 2019 when it was finished all they way in 2016? Is the Ariane 5 a busy launcher?

The telescope was fully assembled at the end of 2016. A fully assembled telescope does not mean a launch-ready spacecraft, however.

The telecope spent pretty much the entirety of 2017 either in transit between various locations, or in long-term tests at those locations - including but not limited a 100-day stint in a vacuum chamber at super-cold temperatures. Now that it has completed all tests, it has been moved to its final integration facility.

There, it will be integrated with the other half - the spacecraft bus. And that, critically, has not been fully assembled for quite the same time as the telescope. They're still testing it, with special focus on the sun shield. Just like nothing quite like the telescope assembly has ever been built before in the history of mankind, the sun shield is also a completely unique mechanism that requires just as much careful attention. It takes a week to deploy, and a month to repackage correctly after deployment tests.

Once all those tests have been completed, the spacecraft bus will be mated with the telescope, and then the entire spacecraft will be tested again. This is what's on the agenda for 2018.

Originally, the launch was scheduled to happen in fall 2018. However, delays with the spacecraft bus have pushed this date back by half a year, into spring 2019. This is sorta convenient for other reasons, too: Ariane 5 is supposed to launch BepiColombo, a major science mission to Mercury, in fall 2018. JWST will require at least a month, maybe two, for payload integration at the launch facility; so as you can see, there was potential for schedule conflict here. And since BepiColombo needs to hit a specific, sorta short transfer window, while JWST can launch whenever it wants, BepiColombo would have definitely received priority.

Now that JWST has been delayed, that schedule conflict has been resolved, which is IMHO good for everyone involved with both of these missions. Let's not rush this.

Edited by Streetwind
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I just hope Webb will not have vision problems, like Hubble suffered at the start of the career :) As of now, we don't have any means to send a repair crew up there to fix things. So, yeah - not rushing and checking everything multiple times should be the order of the day.

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On 11/3/2016 at 2:54 PM, kerbiloid said:

It's Tarsier Telescope mod (at least it's old version), maybe its maintainer would enlarge this.

This should be stunningly easy to do, unless the part files have changed alot since I looked into one.

There should be a numerical scale adjuster value in there somewhere, just set it to whatever to multiply its radius to 3.75.

**edit**

Wow, major necro. You TRICKED me!

Edited by p1t1o
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On 2/15/2018 at 1:06 AM, Scotius said:

I just hope Webb will not have vision problems, like Hubble suffered at the start of the career :) As of now, we don't have any means to send a repair crew up there to fix things. So, yeah - not rushing and checking everything multiple times should be the order of the day.


The big worry for JWST isn't vision problems - it's the Rube Goldbergeque deployment sequence.  There's a lot of moving parts that have to precisely function to bring it to life.  Even if we could get at it, it's not at all clear that anything could be done as so many of said parts are buried deep inside the vehicle.

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  • 1 month later...
2 hours ago, tater said:

Started under 1 B$. Insane.

They are NASA contractors, do you expect different. Well given we are spending 2 bil a year for a launch system that will not technically exist until the middle of next year, its a relative thing.

My point about the STS is that we were faulting the shuttle for overruns and failures that were primarily due to contractor malfeasance and pandering to contractors from the public guidance.

" From its original total cost estimate of about US$400 million, the telescope cost about US$4.7 billion by the time of its launch. " wikipedia - Hubble_Space_Telescope
Then add another 2 billion dollars for the repair mission (Shuttle cost per mission 1.5billion + instrument costs)
Thats in 1993 dollars. That 6.7 billion dollars then hubble would be 11.5 billion dollars if launched today. (Note these are just the cost to get the Hubble working properly, as some of you would likely correct me, the actual cost of 2006 were billions of dollars higher, but then by 2006 the hubbles optics detectors had been near completely upgrade to new instruments; IOW a few billion more for a new telescope)

Value is a relative game, so to speak. It was actually cheaper to keep the Hubble running than replace it simply because its a known, people always go by paper cost, but what you have to look at is the δ$/T$ for the last project cost.(Where the change of cost from proposal to completion is divided by the final cost) If you know what the cost of a repair mission/upgrade mission is based on the last mission it easier in real time to estimate future cost than building and launching something from scratch. But eventually the hubble will reach the end of  a list of potential targets, it might be capable of modification, and then after that . . .obsolete.

We are not going to have 1 Hubble replacement but 2 (WFIRST, almost got cancelled but was revived last week, estimated cost is $3.2B - is essentially a telescope of the Hubble form-factor and will likely be billions higher at operation).

This is what I was saying about the shuttle, its cost were high, but the cost were a known thing, if you completely change things its only exceptional contractors who won't find a way to jack things up and create all kinds of delays.

The exceptional thing about JWST is that its cooling system is way superior to the Hubbles, it can see very close to the edge of the known universe at the hydrogen absortion/emmision spectrum red shifted at 50K. The Hubbles detectors were kept at around 15C (288K) which means they could theoretically detect as low as 5 microns, because the JWST mirrors and main instruments are kept at 50K they can 'see' light that is obscured by the glow of our atmosphere at that temperature. These mirrors on the JWST are larger and can see fainter objects from 600 nm to 5 micron much more clearly than anything the Hubble could see.

300px-Atmospheric_Transmission.png

But the mid-infrared detectors on the JWST can detect down to 27 micrometers a red shift of 270 fold of hydrogens most UV part of lyman series. Given the CMBR is Z=1089 than there are just millions of years differences between the first stars detected at Z=11 (Tbb = 3E8 years) and the matter JWST will try to detect, a small percent difference of the total age of our known Universe. The problem is that these detectors are very sensitive to temperature and the very specialized cooling system on board, if these fail for any reason the advantage of the JWST over known telescopes will be minimal (mainly resolution at high wavelength). Failures may include a faster than expected loss rate of the coolant (which has happened before)

270px-JWST-HST-primary-mirrors.svg.png

There is the claim that there is a service docking port on the JWST such that Orion could service the device if something 'failed' or needed to be repaired. The problem is Orion per flight cost are higher than the shuttles costs; and the mission to go to the JWST at L2, service it, and then return would certainly be in the billions. So we are crossing our fingers hoping the contractors are representing the risk of failure of the sensitive instruments properly. As we recall  the contractor who built the Hubbles mirror did not carefully inspect their work before launch, costing an additional 2 billion dollars.

So if everything works on JWST and works for its stated mission life, 8 9 billion is not too bad. It could be worse (it just got worse).
 

 

Edited by PB666
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2 minutes ago, PB666 said:

 

There is the claim that there is a service docking port on the JWST such that Orion could service the device if something 'failed' or needed to be repaired. The problem is Orion per flight cost are higher than the shuttles costs; and the mission to go to the JWST at L2, service it, and then return would certainly be in the billions. So we are crossing our fingers hoping the contractors are representing the risk of failure of the sensitive instruments properly. As we recall  the contractor who built the Hubbles mirror did not carefully inspect their work before launch, costing an additional 2 billion dollars.

So if everything works on JWST and works for its stated mission life, 8 billion is not too bad. It could be worse.
 

 

The docking port was eliminated long ago.

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