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The James Webb Space Telescope has passed the final mission analysis review

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Re: The James Webb Space Telescope has passed the final mission analysis review

#71

Post by JoeAltmaier »

minikites wrote: post #70
endymi0n wrote: post #69

While it‘s awesome to finally see the JWST finally come to close to launch after all those years, now it‘s a close race between it and SpaceX Starship that could have taken the 6.5 meter mirror up to space in one whole piece in its 9m diameter belly rather than having to do all the miraculous origami that took two decades to develop in the first place…

I wouldn't trust any payload on a SpaceX ship given their track record.

That's how space travel development works. It doesn't take off; it crashes; it explodes; it fails to land; it works. From then on pretty much, it works.

Re: The James Webb Space Telescope has passed the final mission analysis review

#72

Post by systemvoltage »

DubiousPusher wrote: post #65
systemvoltage wrote: post #14

Earlier quoted context omitted.

Another way to put it is that it’s a jobs program. Edit: what’s with the downvotes? I would like to understand what the disagreement is here. Any gov program can be split up into two parts. One, the actual cost as dictated by the market economy, and second, the additional costs for delays, bureaucracy, etc which usually tends to be multiples of the actual costs. This money goes into paying salaries without actually m…

By that logic, so is the military, public schools and highway maintenance.

Any over budget and poorly run government program I see it as a jobs program. F-35, CalTrain, NASA SLS, etc.

This is in stark contrast with partnerships with private industries. For eg DARPA + Moderna or NASA + SpaceX.

Re: The James Webb Space Telescope has passed the final mission analysis review

#73

Post by nrdgrrrl »

ultramegachurch wrote: post #61
jl6 wrote: post #54

If the JWST survives launch but has a subsequent mechanical problem that prevents it deploying properly (and it’s the kind of problem that would have been fixable on Hubble, using a shuttle mission) would it be feasible to mount a robotic rescue mission to chase it down and remote-hands it back to life? For less than the cost of just launching another JWST?

Highly unlikely. That would require designing a new spacecraft from the ground up while also developing new robotics and operations technologies. I'd peg that mission at $300 - $500 million. NASA would almost certainty be better off documenting lessons learned and pursuing a new observatory.

They've spent almost 10 billion dollars on this telescope so far. What's another 0.5 billion for a repair mission?

Re: The James Webb Space Telescope has passed the final mission analysis review

#75

Post by jcims »

lisper wrote: post #9
baggy_trough wrote: post #2

Going to be amazing if this thing can actually unfurl, but I'm scared.

I used to work at JPL, and I was there when the sky-crane (the system currently used to land rovers on Mars) was first proposed back in the late 90s. I remember thinking to myself, "That is the craziest idea I have ever heard, there is no way that could possibly work." But it did. Never bet against NASA engineers. Sure, they have the odd high-profile screwup, but on the whole they are shockingly competent.

Do you know if there is any test footage of that anywhere? That's, to me anyway, the second most amazing thing about the sky crane...that I can't find a single frame of it in operation on earth.

Re: The James Webb Space Telescope has passed the final mission analysis review

#76

Post by keanebean86 »

pkaye wrote: post #50
sonograph wrote: post #33

I remember getting excited about this telescope a decade ago. I haven't heard of it since; but I thought it's budget was cut and it was over. I'm excited NASA is finally going to get it up in space!

Actually the budget was overrun quite a bit. I think it will cost $10B at this point.

$9.5 billion over is pocket change! If you adjust for inflation $10 billion is only $7.7 billion in 2007 dollars. Assuming the telescope works I can live with it being expensive.

Re: The James Webb Space Telescope has passed the final mission analysis review

#77

Post by perihelions »

DubiousPusher wrote: post #63
tomschlick wrote: post #11

Earlier quoted context omitted.

Government red tape and contracting at its finest Edit: Downvotes with no comments as to why... This thing is 24 years in development and 20x over budget. If thats not a failure of government contracting, budgeting, etc then idk what is: https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Cos... - Obviously the platform will be cool once they get it launched, but until then its just a money pit.

It's because this is a flippant, unhelpful attitude. If we were talking about building a mile of blacktop highway then such a casual observation about the overrun might be warranted. But we're not talking about that. We're talking about building the first non-orbital space telescope in human history. To a certain extent, no one could know the actual cost ahead of time. It's one of those things you kind of have to do…

"the first non-orbital space telescope"

There've been a few others, including Gaia (SEL-2 halo orbit -- same as JWST), and Kepler (heliocentric). [edit]: also Herschel (SEL-2)

https://en.wikipedia.org/wiki/Gaia_(spacecraft)#Launch_and_o...

https://en.wikipedia.org/wiki/Kepler_space_telescope#Orbit_a...

https://en.wikipedia.org/wiki/Herschel_Space_Observatory#Lau...

Re: The James Webb Space Telescope has passed the final mission analysis review

#78

Post by mcbutterbunz »

ultramegachurch wrote: post #61
jl6 wrote: post #54

If the JWST survives launch but has a subsequent mechanical problem that prevents it deploying properly (and it’s the kind of problem that would have been fixable on Hubble, using a shuttle mission) would it be feasible to mount a robotic rescue mission to chase it down and remote-hands it back to life? For less than the cost of just launching another JWST?

Highly unlikely. That would require designing a new spacecraft from the ground up while also developing new robotics and operations technologies. I'd peg that mission at $300 - $500 million. NASA would almost certainty be better off documenting lessons learned and pursuing a new observatory.

> I'd peg that mission at $300 - $500 million.

If that was the cost for that mission, it would be worth it considering JWST cost about 20x that amount.

Re: The James Webb Space Telescope has passed the final mission analysis review

#79

Post by DiogenesKynikos »

wthomp wrote: post #51
0xF57A wrote: post #23

I was watching a presentation given by the MGT project manager at cal tech and he mentioned that the MGT has a lower diffraction limit than the JWST. I think “diffraction limit” was the term he used, I don’t remember. The idea was that the images are supposed to be sharper. I was very confused about that. Why build JWST if MGT is going to maker cleaner images?

The diffraction limit is the fundamental resolution limit of a telescope. This is the size of "spot" that will be created on the camera sensor for a single point of light like a star [1]. Its easy to calculate, just take the wavelength of the of light you want to observe and divide it by the diameter of the primary mirror (and multiply by ~1.2). For example, for JWST observing in the mid-infrared, say 4micron, with a…

I'll add to this that resolution is not the only metric by which you can judge a telescope. One major advantage that space telescopes have is that their environment is much more stable, making calibration (for example, of the flux of a source) easier. On Earth, the weather changes from night to night, or even from minute to minute. You're effectively looking through a constantly changing, semi-opaque filter - the atmosphere.

Ground-based telescopes have their own advantages, like the fact that they can be much larger and therefore can collect much more light.

This is just to say that both space- and ground-based telescopes are useful, and have their own strengths.

Re: The James Webb Space Telescope has passed the final mission analysis review

#80

Post by wyldfire »

nabla9 wrote: post #56
jl6 wrote: post #54

If the JWST survives launch but has a subsequent mechanical problem that prevents it deploying properly (and it’s the kind of problem that would have been fixable on Hubble, using a shuttle mission) would it be feasible to mount a robotic rescue mission to chase it down and remote-hands it back to life? For less than the cost of just launching another JWST?

The JWST will not orbit Earth. It will be located near the second Lagrange point (L2) over 1,500,000 km away (The Moon is just 405,000 km from the Earth). Space Shuttle could not have reached it.

How long can it stay stable at that point? Does it have thrusters to keep a station there? If so, how long is the fuel for them provisioned for?

Does use of the thrusters impact the sensors that the telescope uses?

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