Author Topic: Orion for Hubble Service Mission?  (Read 56429 times)

Offline Hog

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Re: Orion for Hubble Service Mission?
« Reply #200 on: 12/15/2014 11:10 AM »
  Depends what your goal is  "better" is subjective in this case.

Even before Hubble was launched, there were techniques that allowed for better resolution from ground bases telescopes, though back in the 90's HST could look at MUCH dimmer objects(edit: 8 magnitudes dimmer than 90's ground based using aperture masking inferiometry).

Its not all about resolution.
"The usefulness of adaptive optics versus HST observations depends strongly on the particular details of the research questions being asked. In the visible bands, adaptive optics can only correct a relatively small field of view, whereas HST can conduct high-resolution optical imaging over a wide field. Only a small fraction of astronomical objects are accessible to high-resolution ground-based imaging; in contrast Hubble can perform high-resolution observations of any part of the night sky, and on objects that are extremely faint."

Creating artificial guide stars using lasers and multi-conjugate AO (adaptive optics) have gone far to mitigate the need for natural AO guide stars and small isoplanatic patch size.  Of course, we can't do much about the night sky brightness, you're right.  But there is JWST coming up, and if it works as intended, it will see far deeper than HST.

But JWST is an IR telescope, with no UV and little if any optical instrumentation (there was a plan to go down to about 650nm, but wasn't it either eliminated or the requirements loosened years ago?  I forget).  There's lots of interesting science that can be done between 91 nm (or 122 for Lyman alpha) and ~400 nm.  The atmosphere blocks light at those wavelengths, but it's where hot stars have most of their really important diagnostic spectral features.  When HST is gone, we won't have much in orbit to do science there, spectroscopy in particular.  I remember a bitter quote from many years ago, lamenting that it would be a shame if we had a Milky Way supernova go off and couldn't observe it in the UV.

Don't get me wrong, I'm as big a fan of space telescopes as you'll find--I used HST!--but at some point we have to let HST go and move on.  I will have a good cry when that happens.  I will especially lament the loss of the UV, though.  I wish we had a plan of regularly (5-7 yrs cadence) launching meter-class or so observatories.  It would be great for spurring instrument and tech development, and there would be many eggs in many baskets.  You could have them focus on particular science areas, with a clear target of opportunity program that's more open.  But alas.
I'm not sure on the visual component of JWST, I do remember that its visual componentry was always a tag on, in order to possibly keep interest in the project.

I like your idea and cadence about meter class observatories, and the advantages that come with it.  Instead of servicing like HST, new observatories take advantage of technological advances.

I think the following graphic illustrates just how far HST and its upgrades have taken us, and what the future may bring.  HST is a baby of the Shuttle era, economical or not, the work that has been done is astonishing.
« Last Edit: 12/15/2014 11:11 AM by Hog »
Paul

Offline newpylong

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Re: Orion for Hubble Service Mission?
« Reply #201 on: 12/15/2014 02:47 PM »
If something is known come right out and say it. We don't get gold stars for guessing hints.

That's an interesting change nonetheless. What is the evidence for the omission?

Servicing a serviceable system in low orbit like HST is complicated. Servicing something that is not designed to be serviceable in L2, like the JWST, is impossible. As simple like that.

You cannot bend the reality of things, and there are  plenty of official resources about the JWST online clearly saying it is not serviceable.

No one is "bending" reality. But others, such as the ones designing JWST obviously have put thought into contingencies, or there wouldn't have been a ring on initial designs or a grapple on the flight article. Call it serviceable, call it last ditch resort, it doesn't make a difference.

Offline jgoldader

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Re: Orion for Hubble Service Mission?
« Reply #202 on: 12/15/2014 04:30 PM »
If something is known come right out and say it. We don't get gold stars for guessing hints.

That's an interesting change nonetheless. What is the evidence for the omission?

Servicing a serviceable system in low orbit like HST is complicated. Servicing something that is not designed to be serviceable in L2, like the JWST, is impossible. As simple like that.

You cannot bend the reality of things, and there are  plenty of official resources about the JWST online clearly saying it is not serviceable.

No one is "bending" reality. But others, such as the ones designing JWST obviously have put thought into contingencies, or there wouldn't have been a ring on initial designs or a grapple on the flight article. Call it serviceable, call it last ditch resort, it doesn't make a difference.

My guess, as I noted earlier, is that the grapple fixture is there in case of some catastrophic deployment failure.  And even then, getting a positive outcome is iffy at best.  Just getting an Orion to JWST would cost billions and take so long the telescope might have died before the capsule even got there.

JWST was designed such that Hubble-type servicing just isn't feasible.  There are no openable bays, and no easily accessed parts that could be replaced. 

A deployment failure is about the only thing a grapple fixture might help fix (call it clumsily analogous to a flat tire in your car), so including the grapple fixture for a last-ditch chance makes some sense (as does having a spare tire) as long as it does not compromise the operation of the telescope.  But HST was designed to have its innards accessible, and JWST is not.  Having a grapple fixture does not make servicing possible.  Having a spare tire in your car is good if you get a flat tire, but useless if the problem is in your engine, and you can't get the hood open.

Designing the telescope in a way that prohibits servicing was a design choice made very early in the project.  The cost of designing with servicing in mind would have been higher, and JWST has always had budget issues; it required a whole lot more tech development than was originally anticipated, IIRC.  The HST servicing missions were some of NASA's greatest triumphs since Apollo, but were quite expensive.  Put simply, that money wasn't going to be there for JWST, and the telescope was designed accordingly.
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Offline pagheca

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Re: Orion for Hubble Service Mission?
« Reply #203 on: 12/15/2014 04:39 PM »
My guess, as I noted earlier, is that the grapple fixture is there in case of some catastrophic deployment failure. 

Is there? Where?

Maybe you mean should have been there?

Offline jgoldader

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Re: Orion for Hubble Service Mission?
« Reply #204 on: 12/15/2014 05:17 PM »
My guess, as I noted earlier, is that the grapple fixture is there in case of some catastrophic deployment failure. 

Is there? Where?

Maybe you mean should have been there?

Others have posted that it IS there.  **IF** is there, then I stand by my post.  And I don't think there's much reason for JWST to have a grapple, as I've noted.
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Offline newpylong

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Re: Orion for Hubble Service Mission?
« Reply #205 on: 12/15/2014 07:07 PM »
If something is known come right out and say it. We don't get gold stars for guessing hints.

That's an interesting change nonetheless. What is the evidence for the omission?

Servicing a serviceable system in low orbit like HST is complicated. Servicing something that is not designed to be serviceable in L2, like the JWST, is impossible. As simple like that.

You cannot bend the reality of things, and there are  plenty of official resources about the JWST online clearly saying it is not serviceable.

No one is "bending" reality. But others, such as the ones designing JWST obviously have put thought into contingencies, or there wouldn't have been a ring on initial designs or a grapple on the flight article. Call it serviceable, call it last ditch resort, it doesn't make a difference.

My guess, as I noted earlier, is that the grapple fixture is there in case of some catastrophic deployment failure.  And even then, getting a positive outcome is iffy at best.  Just getting an Orion to JWST would cost billions and take so long the telescope might have died before the capsule even got there.

JWST was designed such that Hubble-type servicing just isn't feasible.  There are no openable bays, and no easily accessed parts that could be replaced. 

A deployment failure is about the only thing a grapple fixture might help fix (call it clumsily analogous to a flat tire in your car), so including the grapple fixture for a last-ditch chance makes some sense (as does having a spare tire) as long as it does not compromise the operation of the telescope.  But HST was designed to have its innards accessible, and JWST is not.  Having a grapple fixture does not make servicing possible.  Having a spare tire in your car is good if you get a flat tire, but useless if the problem is in your engine, and you can't get the hood open.

Designing the telescope in a way that prohibits servicing was a design choice made very early in the project.  The cost of designing with servicing in mind would have been higher, and JWST has always had budget issues; it required a whole lot more tech development than was originally anticipated, IIRC.  The HST servicing missions were some of NASA's greatest triumphs since Apollo, but were quite expensive.  Put simply, that money wasn't going to be there for JWST, and the telescope was designed accordingly.

I'm with ya. Deployment failure is a scenario I was referring to rather than routine service.
« Last Edit: 12/15/2014 07:07 PM by newpylong »

Offline sghill

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Re: Orion for Hubble Service Mission?
« Reply #206 on: 02/23/2016 07:21 PM »

Then why is there a docking ring on it?

 Are you sure it is still on the spacecraft?

I haven't seen anything that that particular feature has been removed in the design. Have you?

I don't see much evidence that this feature actually made it into the final design, either. I can't find any recent references to any kind of docking or grapple fixture.

Thread bump.

Huh?  A docking ring is right there at minute 14:32 on the video when STS-125 released Hubble. 

Bring the thunder Elon!

Offline Jim

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Re: Orion for Hubble Service Mission?
« Reply #207 on: 02/23/2016 07:45 PM »

Then why is there a docking ring on it?

 Are you sure it is still on the spacecraft?

I haven't seen anything that that particular feature has been removed in the design. Have you?

I don't see much evidence that this feature actually made it into the final design, either. I can't find any recent references to any kind of docking or grapple fixture.

Thread bump.

Huh?  A docking ring is right there at minute 14:32 on the video when STS-125 released Hubble. 


The docking ring was in reference to JWST and not HST

Offline sghill

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Re: Orion for Hubble Service Mission?
« Reply #208 on: 02/25/2016 03:56 PM »

Then why is there a docking ring on it?

 Are you sure it is still on the spacecraft?

I haven't seen anything that that particular feature has been removed in the design. Have you?

I don't see much evidence that this feature actually made it into the final design, either. I can't find any recent references to any kind of docking or grapple fixture.

Thread bump.

Huh?  A docking ring is right there at minute 14:32 on the video when STS-125 released Hubble. 


The docking ring was in reference to JWST and not HST

Ok.  Thank you Jim.  It was driving me nuts.
Bring the thunder Elon!

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