Future Optical Space Telescopes - i.e. Hubble 2.0 ect

[redliox]

With the Hubble celebrating it's 25th Anniversary, it seems prudent to talk about a proper successor to it outside of the James Webb Telescope.  Furthermore, since there isn't a solid optical/ultraviolet space telescope planned for the immediate future, putting this thread here versus Space Science seemed a better match.  After all, by the time the Webb is in space numerous concepts that are advanced now may become feasible for "Hubble's grandchildren."

It'll start with a few pointers and let the rest of you add what you will as long as it relates to space telescopes.
1) Launchers
2) Orbits
3) Goals

The most obvious starting pointing are the rockets to haul up the 'scopes.  After all, the Hubble's size was limited by the shuttle's cargo bay.  The SLS is the most obvious candidate for a large scope; with the core about 8.5 meters wide it would be safe to assume a mirror 8 meters wide could be accommodated in a solid piece, larger if folded like Webb.  However, with SLS tied to politics smaller launchers may economical.  A fairing only 6 meters wide may be the generous norm from a future Vulcan, Falcon, or further future rockets.  On the good news, within 20 years time mirrors made out of essentially plastic could be in use, following a path the proposed MOIRE telescope takes...which means a 'scope crammed into perhaps even a 4 meter fairing could unfold into a mirror 20 meters or even wider.  So, long-term, things will depend more on the mass a rocket sends up instead of just the fairing size...which would give future projects more breathing room despite the sardine can-sizes.

The orbit we put a new telescope into will be another factor, and surprisingly more telescopes are using orbits untouched when Hubble was launched.  Obviously there are both Solar and Lunar Lagrange points, but a better example is TESS: a resonance orbit with the moon is going to be utilized, putting it into an elliptical 14 day high orbit that is surprisingly stable.  Personally, I'd suggest simply putting a new large scope into geostationary orbit for someplace close, easy to track, and very easy to remain in contact with.  Perhaps many orbits could work...but the one I'd be against is LEO; too much garbage is building up in short not to mention it's a pain for astronomers to work around dozens of daily eclipses, Earthshine, and excessive wobbling; the latter will become especially important if the 'scope needs heavy accuracy for exoplanets and extremely deep views.

Then there's the goals to prioritize.  Although infrared is the strong suit for the task, optical and ultraviolet light should be utilized for exoplanet study too especially if the scope is large enough to directly resolve an exoplanet.  There is plenty of work to be done with neighboring galaxies (certainly any within at least a 1/2 billion light years).   On top of that, a UV 'scope might be able to study the afterglow of GRBs with detail (if not the speed) SWIFT had.

What further thoughts are there for future space telescopes?

[RotoSequence]

I really, really want to see an eight meter monolithic, as something for SLS to do. I don't think any other telescope can capture as much light as a monolithic design.

[Coastal Ron]

Regarding launchers, why be limited to any single launcher?

So far it appears the assumption is that we must launch the entire space observatory in one launch, and so we are limited by the size and capabilities of a single rocket.  And if that single rocket is unique, and there are no other options should it become unavailable, that's a bad thing.

The obvious solution is to build future space observatories in space.  And by "build" I mean final assemble of course - put all the final piece parts and modules together in LEO or even beyond.  And those pieces should be able to fit on any of the commodity commercial launchers.  No more worrying about the transportation portion of the plan.

We already have some relevant experience building things in space, since we have already built the 72m x 108m x 20m sized, 450mT mass International Space Station using modular components.  And this is a skill-set we need to improve upon if we want to expand humanity out into space.

We need to get out of the Apollo mindset of single launch missions and that every mission starts on Earth.  It's the 21st Century - let's start acting like it...

[Stormbringer]

Have you guys seen the "glitter" telescope?

http://www.techtimes.com/articles/46747/20150416/hubble-space-telescope-successor-will-glitter-find-alien-life.htm

[catdlr]

Have you guys seen the "glitter" telescope?

http://www.techtimes.com/articles/46747/20150416/hubble-space-telescope-successor-will-glitter-find-alien-life.htm

additional articles:

http://www.jpl.nasa.gov/news/news.php?feature=4553

http://www.nasa.gov/content/orbiting-rainbows/#.VTxd2CFViko

[redliox]

Regarding launchers, why be limited to any single launcher?

So far it appears the assumption is that we must launch the entire space observatory in one launch, and so we are limited by the size and capabilities of a single rocket.  And if that single rocket is unique, and there are no other options should it become unavailable, that's a bad thing.

Ever heard the phase short and sweet?  Any engineer will strive for simplicity whenever possible.  Skylab and Saylut launched with a single launcher...the ISS required over two dozen with the average shuttle flight costing half a billion each.  Skylab had a telescope...the ISS doesn't.

The obvious solution is to build future space observatories in space.  And by "build" I mean final assemble of course - put all the final piece parts and modules together in LEO or even beyond.  And those pieces should be able to fit on any of the commodity commercial launchers.  No more worrying about the transportation portion of the plan.

We already have some relevant experience building things in space, since we have already built the 72m x 108m x 20m sized, 450mT mass International Space Station using modular components.  And this is a skill-set we need to improve upon if we want to expand humanity out into space.

We need to get out of the Apollo mindset of single launch missions and that every mission starts on Earth.  It's the 21st Century - let's start acting like it...

Assembling space stations is an idea older than Apollo.  Von Braun wanted to build giant rotating stations and a fleet of Martian orbiters in his original visions...but as brilliant as he was, he would have failed economics.  The SEI initiative of the 1980s was essentially a reiteration of Von Braun's old extensive plans, and it got shot down fast.  Be careful about invoking a future that was imagined in the past.

As far as assembling a telescope in space, it won't be easy...depending on how extensive the assembly.  If you're doing something simple, like docking a mirror module to the propulsion stage, that's not too big a stretch.  If you're talking astronauts or robots individually setting 100 mirror pieces...don't hold your breath.  Space isn't so much a construction yard, but a high flying circus act.

A constructive alternative could be flying a network of small telescope forming an interferometer, there have been numerous proposals for that in NASA and ESA.  They could either be larger individual satellites or a cluster of cubesats...and if one cubesat is lost it would be cheaper to launch a replacement.

[redliox]

Have you guys seen the "glitter" telescope?

http://www.techtimes.com/articles/46747/20150416/hubble-space-telescope-successor-will-glitter-find-alien-life.htm

additional articles:

http://www.jpl.nasa.gov/news/news.php?feature=4553

http://www.nasa.gov/content/orbiting-rainbows/#.VTxd2CFViko

Seems like a stretch but it could be an advanced way of making a telescope.  I wonder how far such a cluster of mirrors could focus...to a nearby satellite or directly to a telescope on Earth?

[randomly]

This is my favorite so far
SLS launch-able, no speculative development, and can observe exoplanet spectrums out to 100 ly with flying occulters.

http://www.stsci.edu/institute/atlast/documents/ATLAST_NASA_ASMCS_Public_Report.pdf

[redliox]

This is my favorite so far
SLS launch-able, no speculative development, and can observe exoplanet spectrums out to 100 ly with flying occulters.

http://www.stsci.edu/institute/atlast/documents/ATLAST_NASA_ASMCS_Public_Report.pdf

Yup!  I remember that, and it sums up what's needed in the near future if it were affordable.  The concept ought to be reviewed and perhaps even improved upon once the SLS is available.

[Jim]

 8 meter monolithic is not going to happen, there is no way of handling such a spacecraft in the US

[IRobot]

What about g-force limits and vibration limits? The Shuttle had a very low acceleration, but most cargo launchers go up to 6-10g.

[RonM]

8 meter monolithic is not going to happen, there is no way of handling such a spacecraft in the US

Good point.

The Hubble main mirror is 2.4 m. Something bigger would be good, so how large of a monolithic mirror could be launched from the US?

[Coastal Ron]

Ever heard the phase short and sweet?  Any engineer will strive for simplicity whenever possible.

OK, but that has nothing to do with how big something can or should be.  Just look around you.

Skylab and Saylut launched with a single launcher...

Yes, and the Wright Brothers could only carry one passenger on their first airplanes.  Are you suggesting we never should have increased the size or complexity of passenger aircraft?

...the ISS required over two dozen with the average shuttle flight costing half a billion each.

There are lessons to be learned, but you don't want to learn the wrong ones.

The goal of Apollo was "landing a man on the Moon and returning him safely to the Earth", and so Skylab used what was available from that specific Moon-oriented architecture.  It was not a space station optimized architecture, nor was it supposed to be a demonstration of why single-launch was better than multiple-launch architectures for building space-based observatories.

As for the ISS, we had the Shuttle, so we had to use it for construction.  But that's not to say we couldn't build another ISS without the Shuttle and spend far less on transportation costs.  So building the ISS with the Shuttle did not prove that a multiple-launch architecture was too expensive, just that it could be expensive if you use the most expensive choice.

Skylab had a telescope...the ISS doesn't.

Why would we need to turn the ISS into an observatory when you already have much better independent observatories in space?

As far as assembling a telescope in space, it won't be easy...depending on how extensive the assembly.  If you're doing something simple, like docking a mirror module to the propulsion stage, that's not too big a stretch.  If you're talking astronauts or robots individually setting 100 mirror pieces...don't hold your breath.

So echoing your first comment, we'd probably start with just assembling modules into larger assemblies.  We have a lot of experience doing that on the ISS, so this is not some theoretical exercise.

Space isn't so much a construction yard, but a high flying circus act.

OK.  But if we don't become competent in building things in space we won't be able to go far in space.  There is only so much you can do with a single launch architecture.

A constructive alternative could be flying a network of small telescope...

There may end up being many solutions we use, depending on the specific need.

[hop]

The Shuttle had a very low acceleration, but most cargo launchers go up to 6-10g.

This is not really correct. Per the users guides, Atlas 5, Ariane 5 and Soyuz all have sustained loads under 5g. Some of the lighter Delta IV configurations go up to 6, but this can be reduced at the expense of performance.

[Jim]

8 meter monolithic is not going to happen, there is no way of handling such a spacecraft in the US

Good point.

The Hubble main mirror is 2.4 m. Something bigger would be good, so how large of a monolithic mirror could be launched from the US?

Some where in the 3's.

[Hanelyp]

I really, really want to see an eight meter monolithic, as something for SLS to do. I don't think any other telescope can capture as much light as a monolithic design.

What light a mirror loses by being segmented could be made up for with a larger diameter, enabled by being segmented.

[Lee Jay]

8 meter monolithic is not going to happen, there is no way of handling such a spacecraft in the US

Then you can't do the big segmented one either.  Even folded, that mirror is about 17m long and almost 8m wide, designed to fit inside an Ares V 10m fairing.

So, you've either got to build the capability to handle payloads (or one payload) of that size, or you have to limit yourself to a smaller scope (segmented of around 9m or monolithic of around 3m).

[dchill]

With all the talk recently by DLR and the Europeans about far side of the moon operations, etc., I figured somebody else would have already brought up the old idea of putting a spinning liquid mirror on the moon.  <<http://en.wikipedia.org/wiki/Liquid_mirror_telescope#Moon-based_liquid_mirror_telescopes>>

Now we just need somebody to figure out how to keep it liquid at moon temps, have its face be reflective (e.g. assuming you can't use mercury), and for bonus points figure out how to filter out the dust and other contamination caused by being on the the surface of the moon from the liquid.  Once we know how to do all that, then all we need to do is figure out how to transport and land on the moon with barrels full of the liquid, a segmented turn table, and all the other equipment...

It probably doesn't need to be on the far side to perform optical astronomy, but if you've already got astronomers sitting around there doing radio astronomy, why not give them some more equipment to keep running? 

[RotoSequence]

8 meter monolithic is not going to happen, there is no way of handling such a spacecraft in the US

Good point.

The Hubble main mirror is 2.4 m. Something bigger would be good, so how large of a monolithic mirror could be launched from the US?

Some where in the 3's.

What are the limiting factors in the US' payload to space logistics? Is there a consensus that Congress will never allocate an SLS launch for a large mirror monolithic space telescope, or is SLS an unsuitable launch vehicle?

[Coastal Ron]

What are the limiting factors in the US' payload to space logistics?

Depends if you are assembling the observatory in space from components lifted in multiple launches, or it has to be folded up in a single launcher.

Is there a consensus that Congress will never allocate an SLS launch for a large mirror monolithic space telescope?

The SLS is supposed to be the government launcher for government payloads that are too large to fit on commercial launchers.  So I think Congress would be thrilled to hear that the SLS is actually needed for a real payload.

However the real question is whether Congress would want to fund a Hubble replacement that would be large enough to need the SLS...

[KelvinZero]

I would prefer to hear how to build a 100m telescope or 1000 meter telescope, whatever lets us blow past this SLS discussion entirely.

Using SLS to launch a large telescope would be better suited to the HLV forum IMO, but I personally accept Jim's arguments that launching a larger monolithic mirror on a larger rocket is a dead end.

[Burninate]

I would prefer to hear how to build a 100m telescope or 1000 meter telescope, whatever lets us blow past this SLS discussion entirely.

Using SLS to launch a large telescope would be better suited to the HLV forum IMO, but I personally accept Jim's arguments that launching a larger monolithic mirror on a larger rocket is a dead end.

Hubble 2.0 isn't a 100 meter space telescope.  It's a 6.5 meter space telescope (JWST), or a 2.4 meter space telescope (WFIRST-AFTA or shorter wavelength counterpart) with a wider field.  Ideally, Hubble 3.0 would be a fleet of ~4m wide angle telescopes, but I don't discount the possibility that it will be a ~15-25m class analog of JWST.

Building a 100m telescope would involve tiling a bunch of active-optics mirror cells on an in-space-constructed truss system, and it would require a highly streamlined approach to fab, launch, and assemble for less than 100 billion dollars - and I would expect it to take ~20 years or so from inception to completion at the pace we've been working at.  Building a 1000m optical telescope is probably beyond the scope of realistic investment, unless a number of things drop in cost by an order of magnitude.

There's also diffractive telescope concepts that make some sense up to absurd scales using thin film optics, but I'd venture to guess that a 1000m Aragoscope has nowhere near the light-gathering capabilities of a 1000m segmented-glass-mirror telescope (or a 10m segmented-glass-mirror telescope, for that matter).

Another idea is to go beyond the CCD - an optical MKID on the horizon might give phase, R=100 spectral output, and effectively zero-noise (photon-counting) sensitivity over a limited band.  Mix MKIDs with diffraction gratings and you can do other interesting things like tomographic integral field spectrometers in crowded fields.

[Burninate]

If you go far beyond the optical, things look rather different.  We apparently already possess ~20m aperture commercial radio dish antennas, and might even have ~100m aperture ones (probably only to low frequency though) based on rumors of the Orion / Mentor NRO satellites.  Free-flying big-dish radio telescopes with large constellation size are useful for precision interferometry, and there are also proposals to put them in a Lunar Farside Radio Quiet Zone.

We can do quite a bit from the ground with radio.  As you descend from 1mm down to 10um, though, most of that band is not feasible to do through Earth's atmosphere, and detector technologies lag way behind the very effective techniques we have for ~200nm-2000nm (CCD/CMOS variants), the moderately effective thermal infrared bolometers from 2um to 10um, and all the radio technology from 1mm to 1km (and out to 1000km and beyond with progressively lower gain).  Submillimeter orbital interferometer constellations are probably too big to be practicably synchronized, but erecting a ~100m-1km submillimeter megatelescope from an in-orbit-constructed-truss backing is entirely possible - a lot easier than the optical equivalent due to the 1-3 orders of magnitude lower surface accuracy required.

[KelvinZero]

Um.. you understand that 100 and 1000 were just numbers pulled out of my bottom right? The point was whatever is big enough that we can get past that silly conversation of launching on SLS.

You made an interesting assertion about trusses. The earlier link on the glitter telescope specifically mentions no trusses. Will it work? I dunno, but this is advanced topics so this is the right place for it.

[Paul451]

I wonder if the mass-economics of spacecraft design has shifted with the larger launchers on the horizon, whether cheap small-diameter ones like FH or expensive large-diameter ones like SLS. There's no advantage in launching light. That's doubly so with cheap multiple launches on FH. So you need to completely rethink how you design the spacecraft, always ignoring mass and instead focusing (indeed fixating) solely on cost.

So "spending" 5+ tonnes of payload mass on dumb-bulk shielding for off-the-shelf electronics is preferable to spending $100's of millions on specialised rad-hardened electronics. Adding many redundant groups of cheaper systems is better than fewer more-reliable (but more expensive) space-rated systems.

--

But as for design: Judging by JWST, designing around foldable, self-deployable segmented mirrors is expensive. So perhaps a group of 2-3m monolithic mirrors in a simple framed interferometer, launched as separate connecting segments, assembled and tested at the ISS then SEP'd to the final orbit. Think three or more el cheapo versions of HSTs on a triangular or Y-arm truss.

That might get KelvinZero his hundred meter telescope.

[Jim]

The launch costs won't justify Five tons of shielding.  And assembly at the iss is a bad idea for telescopes

[Hanelyp]

And assembly at the iss is a bad idea for telescopes

I agree with the "at ISS" part.  But why is assembly from modules a bad idea for a larger space telescope?  Automated precision near field positioning for docking could be an enabling technology.

[Paul451]

The launch costs won't justify Five tons of shielding.

If a 50t-LEO FH launch costs $150m (with a NASA tax), then every $3m you save in development is worth 1 tonne of wasted payload mass. If adding 5 tonnes of bulk shielding saves more than $15m in development costs, it's worth it.

And assembly at the iss is a bad idea for telescopes

The only negative is orbital inclination, and that's a non-issue if you are using a SEP to reach HEO or ESL.

[Sohl]

Building a 100m telescope would involve tiling a bunch of active-optics mirror cells on an in-space-constructed truss system, and it would require a highly streamlined approach to fab, launch, and assemble for less than 100 billion dollars ...

For example, the "tiles" could be hexagonal modules that can free-fly from a release point to the assembly point, orient and dock with the growing assembly, perhaps using magnetic induction forces (like mlinder experimented with, IIRC) to align before locking into the assembly mechanically.  The interlocking mechanism could be actuated to allow the body of each tile to adjust angles slightly to correct thermal expansion/contraction or other distortion effects, and the primary mirror surface could also be actuated separately to fine-tune the mirror figure to achieve the proper focus. 

If each hexagonal tile was about 1 meter across, several could be launched in a light/medium booster, or as secondary payloads on larger missions.  The main mirror assembly could grow over time as launchers and/or  payload space allow.  Maybe $1 million each, including launch?  Tile 10 thousand of them together for a 100m class mirror, for about $10 billion.  Maybe with mass production line and launcher re-usability, the cost per mirror could be closer to $50K to $100K?  Of course, I'm neglecting the equipment needed to perform main mirror pointing and station-keeping (I like the geosynchronous orbit idea though) and the sensor array module at the focal plane.

edit: wording

[A_M_Swallow]

If we are worried about the exhaust gasses from incoming rockets contaminating the mirror's surface they could dock with a spacestation several miles away. A cable could then connect the flying control room to the partially built telescope. Ordinary electric motors can carry the parts to the telescope for assembly. A small spacestation can now be purchased/long term leased for less than a billion dollars.

[hop]

The only negative is orbital inclination, and that's a non-issue if you are using a SEP to reach HEO or ESL.

Contamination would likely be a concern at ISS. SEP through the Van Allen belts is not really a great thing for the detectors either.

Realistically though, the astronomy community is going to be very lucky to get a telescope that maxes out the payload of a single FH launch (let alone SLS), so on-orbit assembly is unlikely to be relevant.

But as for design: Judging by JWST, designing around foldable, self-deployable segmented mirrors is expensive.

It's reasonable to expect that designing these things will get easier with more experience.

[Coastal Ron]

I would prefer to hear how to build a 100m telescope or 1000 meter telescope, whatever lets us blow past this SLS discussion entirely.

I'll expand on what I suggested earlier about assembling new telescopes in space.

I anticipated that there would be a lot of concern about operating in LEO, and though I can't speak to the challenges of sending telescope modules through the Van Allen Belt, what I think would be doable is to final assemble the telescopes in the region of EML.

If a space station is eventually placed at an EML point in the future, besides being a scientific outpost it could also host temporary construction crews.  If we're ever going to expand humanity out into space we need to find dual use solutions for assets we keep pushing out to the boundaries of where we can operate, so such an arrangement makes sense.

Hopefully this also means we can commoditize the construction of telescopes and other types of observatories, since once you lift the weight and size restrictions, prices for components should drop to some degree.  So instead of spending $8B for building a unique telescope like the JWST, which can not be serviced or upgraded, we could use a generic platform that could easily have components swapped out or upgraded.

Unfortunately I think this is not doable near term, since there doesn't seem to be any serious interest in an EML station, but when we eventually get to that point it could provide a lot of benefits.

[Jim]

The only negative is orbital inclination, and that's a non-issue if you are using a SEP to reach HEO or ESL.

There are many negatives WRT the ISS for telescope assembly.  Among them, it is a dirty environment for optics.  It is basically a nonstarter.

[Jim]

[
If a 50t-LEO FH launch costs $150m (with a NASA tax), then every $3m you save in development is worth 1 tonne of wasted payload mass. If adding 5 tonnes of bulk shielding saves more than $15m in development costs, it's worth it.

LEO is not a destination for telescopes.  Try GEO or L2 or L1 and your numbers don't work for those.

[AncientU]

3.8m is largest that can fit in Delta-IV 5m fairing.  4ish meters is largest practical monolithic mirror size today due to processing facilities, etc., though that could be remedied (some day, but not soon). Even monolithic mirror telescopes are rather 'fluffy' payloads, so generally will be volume limited; mirror areal density of even glass mirrors is around 100kg/m² or less.  DIV-H and FH are or soon will be able to handle this size observatory, but the cost differential favors FH and may shift even more in that direction as D-IV is phased out.  No one is currently building a 4m, though one is being analyzed.

GSO is my choice for survey science (extremely high data rate required) and L-2 seems optimum for point and stare telescopes.  Extreme cooled optics (<50K) and formation flying (such as star shade/telescope pairs) are restricted to Sun-Earth L-2 or drift-away orbits with the latter limited to shorter duration/lower data rate missions.

[Stan Black]

Instead of a circular mirror, is it possible to have a spinning strip or spoke?

[Space Ghost 1962]

I would prefer to hear how to build a 100m telescope or 1000 meter telescope, whatever lets us blow past this SLS discussion entirely.

...
Unfortunately I think this is not doable near term, since there doesn't seem to be any serious interest in an EML station, but when we eventually get to that point it could provide a lot of benefits.

Would have agreed in past. Lately much more interest in EML 1/2. Both in terms of commercial, institutional, and exploration. Examples: Sower's "distributed launch" example of refueling deliveries, resurrecting DTAL, LockMart's Jupiter as arranging Exoliners to pass cargo, numerous international interests in EML 1/2 as a "jumping off" point for post ISS HSF "exploration".

The global space "toolkit" works for EML 1/2, thus international partners see it as a next step. Stands in contrast to the dopey SLS EM-1/2 missions on the board. Good enough for a reliable science product return.

Has interesting possibilities. Could history roll out like:
  * EML 1/2 Gateway
  * Commercial LEO station with nation "tenants in common"
  * ARM(s)
  * Commercial NG space telescope(s) with national "prepay" / "long term" "rent" "service" "upgrade"
  * Mars Phobos mission/station
  * Commercial lunar/asteroid missions
  * Commercial logistics to support national exploration
  * Mars surface expeditions

IP's break the path first. Commercial follows on the path, reducing cost/risk looking for long term means to expansion beyond exploration. Reliable, scalable, economic science product is first return.

Earth telescope observatories are run by consortium's. Why not space based telescopes too?

[Asteroza]

Don't forget hammerhead payload shroud configurations may enable larger (unusual?) monolithic types as well.

Though if some on orbit assembly (as in non-self-deploying requiring full assembly, or externally assisted deploying) is allowed, launching a stack of mirror hexagons, on the face on of it, seems much easier to do.

[catdlr]

A possible future use for the two scopes given to NASA from the defense department?

NASA Mulls Spy Agency's Telescopes for Dark-Energy Mission

http://m.space.com/29192-nasa-spy-satellite-telescopes-space-mission.html

[Burninate]

Don't forget hammerhead payload shroud configurations may enable larger (unusual?) monolithic types as well.

Though if some on orbit assembly (as in non-self-deploying requiring full assembly, or externally assisted deploying) is allowed, launching a stack of mirror hexagons, on the face on of it, seems much easier to do.

It would be a lot of development work to perfect the technique, but it seems workable eventually at the cost of even more active optics supplemental feedback loops.  The JWST folded approach is much easier to do, but it has hard limits on how large it can scale, relative to the payload fairing, and it's much more expensive (at n=1 anyway) than monolithic mirrors.  Building a telescope out of individual mirror cells and constructed trusses would be the next step up (or maybe two steps up) in complexity above that, but could grant you a mirror of almost arbitrary size.

[Jim]

Don't forget hammerhead payload shroud configurations may enable larger (unusual?) monolithic types as well.

It is more than just a fairing and processing facilities.  Need spacecraft factories that can handle spacecraft larger than 5m.  Need vibe, acoustic and thermovac chambers too.  And don't forget a way of getting the spacecraft to the launch site.

[Jim]

The JWST folded approach is much easier to do, but it has hard limits on how large it can scale, relative to the payload fairing, and it's much more expensive (at n=1 anyway) than monolithic mirrors. 

Not a proper comparison.  JWST is 6.5m vs a 5m monolithic.

[RotoSequence]

Don't forget hammerhead payload shroud configurations may enable larger (unusual?) monolithic types as well.

It is more than just a fairing and processing facilities.  Need spacecraft factories that can handle spacecraft larger than 5m.  Need vibe, acoustic and thermovac chambers too.  And don't forget a way of getting the spacecraft to the launch site.

Space Power Facility at Glenn Research Center isn't large enough?

[KelvinZero]

If we are worried about the exhaust gasses from incoming rockets contaminating the mirror's surface they could dock with a spacestation several miles away. A cable could then connect the flying control room to the partially built telescope. Ordinary electric motors can carry the parts to the telescope for assembly. A small spacestation can now be purchased/long term leased for less than a billion dollars.

Getting off topic, but I was wondering if the SEP tug could actually make the Gravity movie's orbital mechanics make sense. Im referring to ISS and Hubble apparently in same orbit, or reachable with very little delta-v. That is the orbit in which you assemble it, and possibly return it for repairs. The SEP tug moves it to and from its working orbit over several months. In that universe it could make sense for the chinese station and any other LEO HSF to be in the same orbit as well, a few hundred miles apart. Shuttling between these locations would be with something not too unlike an Orion or Dragon that is usually docked to the ISS.

[Paul451]

Contamination would likely be a concern at ISS.

Contamination near ISS has been exaggerated. Long-duration exposure experiments haven't found significant issues (unless you get a direct blast from a thruster, obviously.) A 6-12 month construction would not experience significant contamination unless the mirrors were cryo-cooled the entire time.

Realistically though, the astronomy community is going to be very lucky to get a telescope that maxes out the payload of a single FH launch (let alone SLS), so on-orbit assembly is unlikely to be relevant.

That's kind of my point. The availability of cheap launch mass, but not payload-shroud-diameter, may require a change in how you think about designing spacecraft. If heavy-lift additionally frees up significant mass to "waste" on an inefficient design that is cheaper to build, you may get more telescope bang for the buck. (As my previous example of cheap electronics and heavy bulk shielding. Similarly heavy but cheaply built structural elements instead of ultra-light sculpted materials typical of spacecraft.)

SEP through the Van Allen belts is not really a great thing for the detectors either.

But again, when you've got 50 tonnes to play with in a single launch, adding a few tonnes of jettisonable shielding around the instruments isn't a big cost. (Of course, with cheap launches and on-orbit assembly, launching a fast chemical upper-stage as a separate payload might also be an option. But SEP is becoming so off-the-shelf with commercial satellites, it may be the cheaper option.)

LEO is not a destination for telescopes.

Which is why, if you read what I wrote and not what you are pretending I wrote, I didn't say that. You even quoted the part of the comment where I specifically talked about other orbits (including ESL) as the final destination.

[Sohl]

Instead of a circular mirror, is it possible to have a spinning strip or spoke?

I don't see why not... after you capture a series of images over at least a half-rotation, it would be possible to process them all together into higher-resolution approximation of what the fully-filled aperture image would be.  Re-pointing it would be a bit trickier due to gyroscopic effects, and using solar for power also trickier, or perhaps you'd confine your aim to be within something like 30 degrees of the anti-sun direction.

But this kind of setup would be best for targets where image resolution is more important than light-gathering capability... maybe resolving exoplanets separately from their parent stars, measuring star diameters, better resolve face-on binary stars, and other stuff like that.

But yes, this is an interesting idea to think about! 

[AncientU]

<snip>

Earth telescope observatories are run by consortium's. Why not space based telescopes too?

I have a proposal in for just such an observatory...

[Jim]

1.  Contamination near ISS has been exaggerated. Long-duration exposure experiments haven't found significant issues (unless you get a direct blast from a thruster, obviously.) A 6-12 month construction would not experience significant contamination unless the mirrors were cryo-cooled the entire time.


2.  Which is why, if you read what I wrote and not what you are pretending I wrote, I didn't say that. You even quoted the part of the comment where I specifically talked about other orbits (including ESL) as the final destination.

1.  Wrong context and take away.  It isn't "significant" for the experiments and vehicles that visit it and not applicable to telescope optics.    Your points on 6-12 months and optic temps are unsubstantiated.


2.  Then don't make a  claim of 50 tons with 5 tons of shielding.  The mass to those actually orbits is significantly less.  There is no need for SEP when a launch vehicle can get it there directly.  There is no real savings.

3.  This  nonsense  "heavy-lift additionally frees up significant mass to "waste" on an inefficient design that is cheaper to build"  is not proven and doesn't look like it will

[Jim]

Space Power Facility at Glenn Research Center isn't large enough?

a.  It can't do true thermal vac
b.  can't get to it.  There are too many obstructions between it and the airport.

[RonM]

Instead of a circular mirror, is it possible to have a spinning strip or spoke?

I don't see why not... after you capture a series of images over at least a half-rotation, it would be possible to process them all together into higher-resolution approximation of what the fully-filled aperture image would be.  Re-pointing it would be a bit trickier due to gyroscopic effects, and using solar for power also trickier, or perhaps you'd confine your aim to be within something like 30 degrees of the anti-sun direction.

But this kind of setup would be best for targets where image resolution is more important than light-gathering capability... maybe resolving exoplanets separately from their parent stars, measuring star diameters, better resolve face-on binary stars, and other stuff like that.

But yes, this is an interesting idea to think about! 

Sorry, that won't work. Vibrations would be a problem, ruining the resolution. Less area equals less light gathering capability.  Defeats the purpose of having a larger mirror.

If the need is for a Hubble replacement, then something a little larger with modern electronics is the solution.

If the need is to resolve exoplanets, then multiple telescopes acting as an interferometer is the solution.

[Sohl]

Instead of a circular mirror, is it possible to have a spinning strip or spoke?

I don't see why not... But yes, this is an interesting idea to think about! 

Sorry, that won't work. Vibrations would be a problem, ruining the resolution. Less area equals less light gathering capability.  Defeats the purpose of having a larger mirror.

If the need is for a Hubble replacement, then something a little larger with modern electronics is the solution.

If the need is to resolve exoplanets, then multiple telescopes acting as an interferometer is the solution.

I envisioned the long "strip or spoke" might be a relatively rigid framework for an optical long(ish)-baseline interferometer.  http://en.wikipedia.org/wiki/Astronomical_interferometer

Active vibration damping or passive rigidity could be engineered in as needed.  Might be easier than a pair or larger numbers of free-flying interferometer mirros, no?  As I pointed out, it would have its limitations though.

Edit:  That said, I would like to add that I'd like to see a somewhat bigger, better version of optical/UV Hubble flown for general-purpose astronomy too (and probably first, before the more exotic concepts I and others have shared).

[Paul451]

I envisioned the long "strip or spoke" might be a relatively rigid framework for an optical long(ish)-baseline interferometer.

If it's an interferometer, you don't need the rotation. Just two smaller 'scopes on a truss. (Or three or four on a y-arm or triangular truss.)

before the more exotic concepts I and others have shared

Oddly, this kind of interferometer would be much simpler than a large conventional telescope, it just wouldn't give you the classic HST astronomy-porn images.

It isn't "significant" for the experiments and vehicles that visit it and not applicable to telescope optics.

Jim, you know damn well that long-duration exposure experiments (including MISSE) have included mirror elements.

[Jim]

Jim, you know damn well that long-duration exposure experiments (including MISSE) have included mirror elements.

And the results can't hand waved away as not "significant"

[Sohl]

Oddly, this kind of interferometer would be much simpler than a large conventional telescope, it just wouldn't give you the classic HST astronomy-porn images.

No, not for a single interferogram image capture, but if you combine the interferogram from multiple angles, you can synthesize  something close to a conventional image.  That would be the motivation for rotating.  Multiple arms could provide even more data for better full-image estimation accuracy and low-light sensitivity.

Look, I'm not saying this is the best thing to promote as a high priority now, but the initial post struck me as an interesting and innovative approach to a capability we don't have now: ultra-high resolution from an atmosphere-free observatory.  It could be a stepping stone to massive in-space mirror telescopes.  But, yeah, for a presumed Hubble 2.0, probably not the best approach.

[llanitedave]

8 meter monolithic is not going to happen, there is no way of handling such a spacecraft in the US

That's simply not true, Jim.  You've been corrected on that claim before with specific examples.  8 meter monolithic mirrors are being produced right now in Phoenix, Arizona, and are being shipped on public roads.

[Jim]

That's simply not true, Jim.  You've been corrected on that claim before with specific examples.  8 meter monolithic mirrors are being produced right now in Phoenix, Arizona, and are being shipped on public roads.

Wrong and those were corrections were wrong too.  I have been saying spacecraft not just a mirrors.

[gosnold]

Membrane optics might be the way to go. They can give large, lightweight apertures albeit with reduced collecting efficiency (around 30% currently) and restricted bandwitdth.

[llanitedave]

That's simply not true, Jim.  You've been corrected on that claim before with specific examples.  8 meter monolithic mirrors are being produced right now in Phoenix, Arizona, and are being shipped on public roads.

Wrong and those were corrections were wrong too.  I have been saying spacecraft not just a mirrors.

The mirror is the largest single component, and the only one that would even potentially cause problems due to size.  There is no reason for NASA to be considering an 8.5 meter fairing if they have no plans to develop the capability of  handling payloads that require it.


The corrections were factual, BTW.  I listed specific examples of monolithic mirrors produced by spin casting, 8m in diameter, from the University of Arizona, that have been transported out of Phoenix and are being installed in major observatories worldwide.  Please don't misrepresent me.

[Jim]

1.  The mirror is the largest single component, and the only one that would even potentially cause problems due to size. 

2.  There is no reason for NASA to be considering an 8.5 meter fairing if they have no plans to develop the capability of  handling payloads that require it.

3.The corrections were factual, BTW.  I listed specific examples of monolithic mirrors produced by spin casting, 8m in diameter, from the University of Arizona, that have been transported out of Phoenix and are being installed in major observatories worldwide.  Please don't misrepresent me.

1.  Wrong again.  It is not just the mirror.  It would be part of a larger telescope assembly and then yet part of a spacecraft.    So, it doesn't matter if they can get a mirror around.  The issue is the telescope assembly and the spacecraft

2. Surely you jest.  The only thing they really look at was the LSAM and that could be broken down into pieces.  There are only pie in the sky ideas like ALAST.  There is no real look at the money needed to pull it off.   Why do you think JWST costs so much?  It is still within existing fairings and can use existing planes, but still needed a new dedicated container and transporter.    Itt has to be tested in the deployed configuration and there was only one place that was large enough to test it.  They had to modify the JSC thermovac chamber and build a clean room around it.

3.  No, the corrections were meaningless since I was talking about spacecraft.

[wizzzard3]

use spiderbot

[gosnold]

use spiderbot

It won't produce optical-quality surfaces, but it could be interesting for a radio telescope at high frequencies

[Burninate]

A telescope assembly is constrained by the size of the mirror, but also by structural elements of the mirror cell and the truss (which must fall outside the FOV of the mirror aperture's edges to avoid vignetting).  Hubble has a 2.4m mirror but the two cylindrical body sections have diameter 2.9m (the outer edge of the optical tube) and 4.2m (an instrument, power, & avionics bay behind it).  http://hubblesite.org/the_telescope/hand-held_hubble/the_real_thing.php#size

It's hard to generalize, but the optical tube assembly being ~20% larger than the mirror itself is probably a good starting estimate.  Outside of the optical tube, the rest of the telescope's diameter is going to depend *heavily* on the configuration choices that the designers made, and might be half the size of the OTA or twice the size.

[the_roche_lobe]

Slightly tangental because the talk is about ground based exoplanet telescope innovation, but here:



Is a very interesting recent talk about radically lightening mirror segments (second half of the talk) by using UNPOLISHED commercial float glass, slumping, and fine figure control entirely by active sensors!

I'm skeptical, but if it works it promises a revolution in space-based mirror surfaces as well.

P

[Burninate]

Slightly tangental because the talk is about ground based exoplanet telescope innovation, but here:



Is a very interesting recent talk about radically lightening mirror segments (second half of the talk) by using UNPOLISHED commercial float glass, slumping, and fine figure control entirely by active sensors!

I'm skeptical, but if it works it promises a revolution in space-based mirror surfaces as well.

P

Before watching the talk:
Slumping to form (on smaller mirrors) and fine figure control by active sensors (on larger mirrors) are existing techs.  Generally, float glass is rather wasteful for large telescopes - the mass costs scale better with commodity borosilicate blends.  There are specialty glasses with better thermal or better rigidity properties, but they're very expensive and have some compromises.

I watched Kuhn's previous talk on the Colossus, from a few years ago:


And I thought that the revolutionary bit was that they were solving for phase differences of up to 10^2 waves from one side of the mirror array to the other *in software*, albeit over a tiny FOV.  A true imaging interferometer, with software coronography, albeit over single-digit arc-seconds, without needing to penetrade the extremely difficult step of fringe-tracking optical correlators and 20nm precision alignment.  The telescope is extraordinarily specialized though - it's pretty much only good for imaging one point source in a pencil beam, and he explicitly declares that it's not even being presented as an astronomical facility, only a SETI facility.  In response to that I say "Good luck getting that funded".

Watching the new talk now.

[tea monster]

The cost of a space telescope isn't so much in the mirror glass itself. It's in logistics, software, spacecraft buss, thermal/attitude control and then hauling the whole kaboodle up into orbit. After that, you have to hire a room full of spacecraft engineers to maintain and look after the thing.

[llanitedave]

A telescope assembly is constrained by the size of the mirror, but also by structural elements of the mirror cell and the truss (which must fall outside the FOV of the mirror aperture's edges to avoid vignetting).  Hubble has a 2.4m mirror but the two cylindrical body sections have diameter 2.9m (the outer edge of the optical tube) and 4.2m (an instrument, power, & avionics bay behind it).  http://hubblesite.org/the_telescope/hand-held_hubble/the_real_thing.php#size

It's hard to generalize, but the optical tube assembly being ~20% larger than the mirror itself is probably a good starting estimate.  Outside of the optical tube, the rest of the telescope's diameter is going to depend *heavily* on the configuration choices that the designers made, and might be half the size of the OTA or twice the size.

That's not necessarily the case.  We visualize mirrors in tubes, but, especially in a space telescope, an external tube is completely unnessecary.


The Spitzer Space Telescope is a case in point:





All instrumentation and mirror mounting gear can be hidden below the mirror itself, and the primary is the only part that needs to be in one piece (assuming a monolithic mirror)  All the instruments and supporting trusses can be parts of smaller assemblies that can be handled separately.


There's no reason to cling to the mindset of futility that just assumes it can't be done.

[Jim]

That's not necessarily the case.  We visualize mirrors in tubes, but, especially in a space telescope, an external tube is completely unnessecary.

The Spitzer Space Telescope is a case in point

All instrumentation and mirror mounting gear can be hidden below the mirror itself, and the primary is the only part that needs to be in one piece (assuming a monolithic mirror)  All the instruments and supporting trusses can be parts of smaller assemblies that can be handled separately.

No, wrong again.

A.  There was a light shield around the telescope.  Most will need one or a deployable one.
b.  The telescope was very small so the secondary mirror is not a big deal.  The secondary mirror on a large telescope will be bigger than the Spitzer spacecraft itself.
c.  All the instruments and supporting trusses still have to attached to the telescope and tested before delivery to the launch site. 

testing - including acoustic, random vibe or modal survey, and thermo vac.

[Jim]

And to use your example against you, the rest of the spacecraft is larger than the telescope.

[Oli]

2. Surely you jest.  The only thing they really look at was the LSAM and that could be broken down into pieces.  There are only pie in the sky ideas like ALAST.  There is no real look at the money needed to pull it off.   Why do you think JWST costs so much?  It is still within existing fairings and can use existing planes, but still needed a new dedicated container and transporter.    Itt has to be tested in the deployed configuration and there was only one place that was large enough to test it.  They had to modify the JSC thermovac chamber and build a clean room around it.

So you think telescopes bigger than JWST won't happen because they're too expensive? What's the alternative to bigger telescopes?

[llanitedave]

And to use your example against you, the rest of the spacecraft is larger than the telescope.

That's irrelevant to what I'm talking about.  Spitzer was an infrared instrument that needed shielding, it was in low Earth orbit  as well.


An optical instrument in a high orbit does not need the shielding, and as long as you were in the mood to go searching for images, you should have found abundant examples of observatory telescopes that do not need tubes.  The largest telescopes have observatory clamshells for protection from the weather, but when in use, they are mostly exposed.  A large space telescope can get by just fine without a tube.


In fact, JWST does not have a tube either, which your attempted counterexample seems to miss.  The fact remains that an 8 meter monolithic mirror, minus maybe a small amount to accommodate the inner fairing, can be launched on SLS with an 8.5 meter fairing.  You don't need to add space for a tube.  It's a non-problem, and an artificial objection.

[hop]

And to use your example against you, the rest of the spacecraft is larger than the telescope.

That's irrelevant to what I'm talking about.

The fact that Spitzer actually uses the classic mirror in a tube design hardly seems irrelevant. Even if you are correct, the example you chose does not support your argument.

Spitzer was an infrared instrument that needed shielding, it was in low Earth orbit  as well.

Spitzer is in an earth-trailing heliocentric orbit.

JWST and Herschel are examples of space telescopes that forgo the tube, but neither contradicts Jim's point about generally needing structures larger than the primary mirror.

[Jim]

In fact, JWST does not have a tube either, which your attempted counterexample seems to miss.  The fact remains that an 8 meter monolithic mirror, minus maybe a small amount to accommodate the inner fairing, can be launched on SLS with an 8.5 meter fairing.  You don't need to add space for a tube.  It's a non-problem, and an artificial objection.

I never said it couldn't be "launched".  I said we don't have the infrastructure in the country to build and test it for flight.
It is not a non-problem, It is a very very expensive problem and it is a failure on your part to understand this simple concept.

JWST has a giant deployable sun shield (Hershel has a fixed one which still makes my point), which any SLS telescope spacecraft would need an even larger one.  Another facility which does not exist.

Also, JWST's mirrors are in a vertical plane which reduces it susceptibility to contamination.  A large mirror in the horizontal plane would need covers.

Also look at SIRTF, Herschel and JWST, the instruments and spacecraft bus are still a significant size compared to the telescope.

All the concepts here:  http://www.stsci.edu/atlast either have a tube or a large deployable sunshield.  All the concepts ignore the ground infrastructure much like JWST did and will incur large cost increases.

[llanitedave]

And to use your example against you, the rest of the spacecraft is larger than the telescope.

That's irrelevant to what I'm talking about.

The fact that Spitzer actually uses the classic mirror in a tube design hardly seems irrelevant. Even if you are correct, the example you chose does not support your argument.

Spitzer was an infrared instrument that needed shielding, it was in low Earth orbit  as well.

Spitzer is in an earth-trailing heliocentric orbit.

JWST and Herschel are examples of space telescopes that forgo the tube, but neither contradicts Jim's point about generally needing structures larger than the primary mirror.

Thanks for the correction on the orbit, but my point still stands.  The Spitzer's tube is not structural.  The supporting structure of the telescope is the mirror-mounting framework on the back, and the central support that comes up through the central perforation of the primary mirror.  There is no need for any structure outside the primary's diameter.


The tube was necessary ONLY because it is an infrared instrument and needed thermal protection.  It doesn't need it for structure, didn't need it for glare, and didn't need it to protect against launch vibrations.


An optical telescope can just as easily use a similar structural design, and can just as easily dispense with the tube.  If it still needs a sunshade, a rollout structure can be fitted to the base, one that would be far simpler than what the JWST needs.


Regardless of design details, there's nothing about an 8 meter monolithic mirror that precludes it from launching on an SLS-class rocket.


Jim, I acknowledge the lack of ground infrastructure for such instruments, and that's a valid point, but it's far from a deal-breaker.  If the SLS is going to carry larger payloads, then a larger assembly facility will have to be built anyway.  I don't envision that a single 8 meter telescope is the only package that calls for an 8.5 meter fairing.

[Jim]

If the SLS is going to carry larger payloads, then a larger assembly facility will have to be built anyway. 

That's the point, it is a deal breaker.  There is no money for such payloads much less the infrastructure upgrades.

The Cape/KSC would only need a processing facility.  The nation (meaning spacecraft  contractors and users) needs bigger manufacturing facilities like in Denver, Sunnyvale, Palo Alto, El Segundo, Renton, Redondo Beach, JPL, GSFC, etc.  And testing facilities and transportation systems to go between them.  Right now, everything is centered around 5m and still not many facilities can handle it.

tens of billions of dollars.

[Jim]

If it still needs a sunshade, a rollout structure can be fitted to the base, one that would be far simpler than what the JWST needs.

That is not true either.  It is not that simple

[Todd Martin]

Just a couple comments. 

It may be lost on some that the light collecting ability of a telescope is not linear to primary mirror diameter.  Hubble has a 2.4 meter diameter lens, which translates to 4.52 m^2 of surface area (Pi * R^2).  If we choose to replace Hubble with a 4 meter diameter lens telescope, the surface area increases to 12.57 m^2, which is a 278% increase in light gathering power.  We don't have to replace all the ground testing lab equipment to get an upgrade of over double the power of Hubble.  And this is without folding mirrors.

Secondly, Hubble has been popular in large part because of the spectacular images.  JWST simply won't provide that and public support for space astronomy will suffer.  That popularity allowed for NASA to do several servicing missions over the years.  I think a "Save the Hubble" mission could still be started today if the Scientific community would decide it was a priority.   

[Oli]

If the SLS is going to carry larger payloads, then a larger assembly facility will have to be built anyway. 

That's the point, it is a deal breaker.  There is no money for such payloads much the infrastructure upgrades.

The Cape/KSC would only need a processing facility.  The nation (meaning spacecraft  contractors and users) needs bigger manufacturing facilities like in Denver, Sunnyvale, Palo Alto, El Segundo, Renton, Redondo Beach, JPL, GSFC, etc.  And testing facilities and transportation systems to go between them.  Right now, everything is centered around 5m and still not many facilities can handle it.

tens of billions of dollars.

Off topic but how was Skylab tested? According to wiki it cost $10bn in 2010 dollars.

[RotoSequence]

If the SLS is going to carry larger payloads, then a larger assembly facility will have to be built anyway. 

That's the point, it is a deal breaker.  There is no money for such payloads much the infrastructure upgrades.

The Cape/KSC would only need a processing facility.  The nation (meaning spacecraft  contractors and users) needs bigger manufacturing facilities like in Denver, Sunnyvale, Palo Alto, El Segundo, Renton, Redondo Beach, JPL, GSFC, etc.  And testing facilities and transportation systems to go between them.  Right now, everything is centered around 5m and still not many facilities can handle it.

tens of billions of dollars.

How many different, single parts of the space telescope scale with the size of the main mirror, would require new/unique tooling, have unique transportation needs that cannot be met with existing infrastructure, and/or need to be independently tested and evaluated before being shipped to NASA?

[Jim]

How many different, single parts of the space telescope scale with the size of the main mirror, would require new/unique tooling, have unique transportation needs that cannot be met with existing infrastructure, and/or need to be independently tested and evaluated before being shipped to NASA?

The testing of a spacecraft is done at the factory and not at the launch site.  And it is done as a complete spacecraft as possible.

[Jim]

Off topic but how was Skylab tested? According to wiki it cost $10bn in 2010 dollars.

Skylab was a rocket stage and not a spacecraft.  But the ATM was treated as a science spacecraft.

Science spacecraft have closer thermal interactions between the spacecraft and instruments.

[a_langwich]

Secondly, Hubble has been popular in large part because of the spectacular images.  JWST simply won't provide that and public support for space astronomy will suffer.  That popularity allowed for NASA to do several servicing missions over the years.     

A great chunk of NASA's images, including Hubble images, that are shown today include a fair amount of information from outside the visible spectrum.  The gorgeous thing about Hubble images isn't a visible-spectrum lighting special effect, it's the wonderful structure and complexity and awe-inspiring scale of the universe.  It's entirely possible to generate spectacular visual images from JWST.  Parts of them ARE perfectly normal visible light images, just red-shifted by velocity. 

Part of the fascination behind the Hubble images is the science behind it, and at least the implication there are exciting new discoveries coming from it, rather than just a really hi-res version of the image you could get at a star-gazing party.  So just making a dedicated multi-billion star-party imager is likely to lose a little bit of the wonder. 

JWST overlaps Hubble capabilities, up into the visible spectrum.

I think a "Save the Hubble" mission could still be started today if the Scientific community would decide it was a priority.

That is precisely the problem:  it is NOT a _scientific_ priority.  For the limited amount of money they have, it's not on the priority list. 

But, if you think the popular support for Hubble-like images really is worth several billion dollars (as in the servicing missions), and won't be met by JWST or all the terrestrial big 'scopes for some reason, there's hope!  Simply raise the billion and a half or two in a foundation, and fund the launching of the second of the Hubble-sized mirrors NASA was given as a Hubble visible-light follow-on.  The first NASA hopes to use for WFIRST, but everything I've read suggests they don't have the money to use the second.  Or, if you think only a 4-5m size is the minimum for your tastes, fund that.  If people want it enough to put their money to it, then it's no problem.

I think there are plans afoot to do something like that (private consortia for space telescopes), on a smaller scale.  University consortia can raise on the order of a billion, so IF you can provide value on the level of a terrestrial Thirty Meter Telescope or the like, it can be privately done.  The terrestrial telescopes can have a much longer useful working life, but a space telescope offers much higher utilization rates during its life.  The terrestrial telescopes would be massively larger for the same budget, and more easily upgraded with more advanced adaptive optics and electronics, but the space telescope offers unique advantages of a tiny point spread function, the ability to look virtually anywhere in the sky at a time (if in a distant orbit), or stare for extended periods of time.  The space telescope will also require a ground terminal facility able to communicate with the observatory as many hours of the day as you wish to do science, which may imply ground stations spaced around the globe or an orbital relay facility.  Or you could try to pay NASA for DSN use, but it probably costs more than you could afford.

[Coastal Ron]

If the SLS is going to carry larger payloads, then a larger assembly facility will have to be built anyway. 

That's the point, it is a deal breaker.  There is no money for such payloads much the infrastructure upgrades.

A very good point, and one that SLS supporters don't seem to be aware of.

The SLS has an 8.4m diameter core, so any SLS-sized payloads are likely to be larger than what could fit in the current EELV sized launchers (~5m in diameter).

As you point out Jim, current payloads can be transported by road or by aircraft, but there are limits.  The U.S. Interstate freeway system limits payloads to 14-16 ft in total height, and a C-5 can only carry cargo that is up to 13.5ft in height.  Even the An-225, the largest cargo aircraft in the world, can only carry cargo that is up to 14ft in height.

So SLS-sized payloads will have to be built close to water transportation, which limits using existing facilities.  But even those existing facilities would have to create new infrastructure and tooling to handing SLS-sized payload manufacturing and testing.  Sure we have built rockets of that size before, but not payloads.

So there are costs associated with setting up a factory that has to be absorbed by the first product that is produced.  If more are produced the average costs can go down, but if we're talking about a single replacement for the Hubble, then the costs of building an HLV-sized monolithic platform could be very considerable.

[Jim]

and a C-5 can only carry cargo that is up to 13.5ft in height. 

There are two C-5's that can carry a 15' x 45' payloads

[Lee Jay]

If the SLS is going to carry larger payloads, then a larger assembly facility will have to be built anyway. 

That's the point, it is a deal breaker.  There is no money for such payloads much less the infrastructure upgrades.

The Cape/KSC would only need a processing facility.  The nation (meaning spacecraft  contractors and users) needs bigger manufacturing facilities like in Denver, Sunnyvale, Palo Alto, El Segundo, Renton, Redondo Beach, JPL, GSFC, etc.  And testing facilities and transportation systems to go between them.  Right now, everything is centered around 5m and still not many facilities can handle it.

tens of billions of dollars.

I don't know a lot about these facilities, but a quick search revealed this:

http://facilities.grc.nasa.gov/documents/TOPS/TopPB.pdf

It says the facility can handle 100 foot diameter by 122 foot long items.  That's 30.5m x 37.2m.  It's apparently located where such objects can be shipped by water transport.  I would think that they wouldn't have built such a large facility if such objects could not be built or shipped, but like I said I don't know a lot about it.

The entire site has a total current replacement value of more than $877.5 million, but that includes a lot of buildings and facilities having nothing to do with the SPF.

http://oig.nasa.gov/audits/reports/FY15/IG-15-014.pdf

I'm not sure if the facility would require some upgrades to vibration actuators, modal testing equipment and so forth (the acoustic test facility looks a little marginal at 11.4m by 14.5m 17.4m), or not, but it seems that at least some facilities exist to handle extremely large spacecraft.  The acoustic chamber is only listed as a $30M facility and the vibration facility is listed at $25M so maybe "tens of billions of dollars" is a little excessive even though it will include processes besides testing, including production.

[Jim]

It says the facility can handle 100 foot diameter by 122 foot long items.  That's 30.5m x 37.2m.  It's apparently located where such objects can be shipped by water transport.  I would think that they wouldn't have built such a large facility if such objects could not be built or shipped, but like I said I don't know a lot about it.

The SPF isn't a thermovac chamber.  Just a vacuum chamber (need better vacuum, sun lights and cryogenic cooling)  Water transport is no good if the origination facilities are not on water.  JWST is going to JSC vs GRC because of items like this

[llanitedave]

If the SLS is going to carry larger payloads, then a larger assembly facility will have to be built anyway. 

That's the point, it is a deal breaker.  There is no money for such payloads much the infrastructure upgrades.

A very good point, and one that SLS supporters don't seem to be aware of.

The SLS has an 8.4m diameter core, so any SLS-sized payloads are likely to be larger than what could fit in the current EELV sized launchers (~5m in diameter).

As you point out Jim, current payloads can be transported by road or by aircraft, but there are limits.  The U.S. Interstate freeway system limits payloads to 14-16 ft in total height, and a C-5 can only carry cargo that is up to 13.5ft in height.  Even the An-225, the largest cargo aircraft in the world, can only carry cargo that is up to 14ft in height.

So SLS-sized payloads will have to be built close to water transportation, which limits using existing facilities.  But even those existing facilities would have to create new infrastructure and tooling to handing SLS-sized payload manufacturing and testing.  Sure we have built rockets of that size before, but not payloads.

So there are costs associated with setting up a factory that has to be absorbed by the first product that is produced.  If more are produced the average costs can go down, but if we're talking about a single replacement for the Hubble, then the costs of building an HLV-sized monolithic platform could be very considerable.

Keep in mind, Ron, 8 meter monolithic telescope mirrors are cast and polished in Phoenix, Arizona, under the University of Arizona football stadium.  There's no water transport there.  These mirrors, fragile as they may seem, are placed in containers for transport, and are taken on public roads to remote mountaintops where they are surrounded by clean facilities that allow for their maintenance.


It's hard to believe that NASA can't afford the scale of facilities that other observatories, which are also operating on shoestring budgets, manage to provide.

[Lee Jay]

It says the facility can handle 100 foot diameter by 122 foot long items.  That's 30.5m x 37.2m.  It's apparently located where such objects can be shipped by water transport.  I would think that they wouldn't have built such a large facility if such objects could not be built or shipped, but like I said I don't know a lot about it.

The SPF isn't a thermovac chamber.

It is, sort of.

"The chamber can sustain a high vacuum (10-6 torr); provide an optically-tight, high-emissivity, thermal background environment of -250 °F to +140 °F within the 40-foot diameter by 40-foot high variable-geometry cryogenic shroud. "

http://facilities.grc.nasa.gov/spf/

I'm sure that building a bigger shroud, if necessary, wouldn't be an expensive thing to do in the context of a ~$10B telescope.

Water transport is no good if the origination facilities are not on water.

So you do final assembly somewhere other than where the components are manufactured, perhaps even at a facility like the SPF.

The point is, we have manufactured and transported very, very large items in this country (much larger than a hypothetical 8.4m monolithic telescope), and for a one-off thing like this, we could do it if we wanted to and without an investment that matches or exceeds the ~$10B cost of the item.  It wouldn't be cheap or easy, but it could be done and the transport and testing of the item wouldn't be a significant limiting factor.  It would cost some money and time, but it could be done, and for a lot less than "tens of billions" (excluding the spacecraft itself).

[Jim]

It is, sort of.

"The chamber can sustain a high vacuum (10-6 torr); provide an optically-tight, high-emissivity, thermal background environment of -250 °F to +140 °F within the 40-foot diameter by 40-foot high variable-geometry cryogenic shroud. "

Spacecraft are not using it because it not good enough and it is too far away from an airport.

[Jim]

Keep in mind, Ron, 8 meter monolithic telescope mirrors are cast and polished in Phoenix, Arizona, under the University of Arizona football stadium.  There's no water transport there.  These mirrors, fragile as they may seem, are placed in containers for transport, and are taken on public roads to remote mountaintops where they are surrounded by clean facilities that allow for their maintenance.

Wrong analogy.  Mirror has nothing do with it. An observatory is not a spacecraft manufacturing facility.   The issue is large spacecraft in general.  Handling just a mirror is not the same as handling a spacecraft and a bad example.   They are  two completely different tasks.    A mirror is small compared to a spacecraft.  It is transported  horizontally, and is just a wide load, which is easy.  It isn't transported in this orientation.

[Jim]

Which it would have to be as a telescope like this one.

[Jim]

And taking your SIRTF example, the secondary mirror and support would too tall to transport like your Arizona mirrors.

[Jim]

The point is, we have manufactured and transported very, very large items in this country itself).

But not kept them in a clean and conditioned environment at the same time.

 and for a one-off thing like this, we could do it if we wanted to and without an investment that matches or exceeds the ~$10B cost of the item.

That's the point, because isn't cheap or easy, it is a one-off thing.  So what else is SLS going to fly?

we could do it if we wanted to and without an investment that matches or exceeds the ~$10B cost of the item.  It wouldn't be cheap or easy, but it could be done and the transport and testing of the item wouldn't be a significant limiting factor.  It would cost some money and time, but it could be done, and for a lot less than "tens of billions" (excluding the spacecraft itself).

Where do you think most JWST's money is going?  Not the spacecraft.

[Mr. D]

If the SLS is going to carry larger payloads, then a larger assembly facility will have to be built anyway. 

That's the point, it is a deal breaker.  There is no money for such payloads much the infrastructure upgrades.

A very good point, and one that SLS supporters don't seem to be aware of.

The SLS has an 8.4m diameter core, so any SLS-sized payloads are likely to be larger than what could fit in the current EELV sized launchers (~5m in diameter).

As you point out Jim, current payloads can be transported by road or by aircraft, but there are limits.  The U.S. Interstate freeway system limits payloads to 14-16 ft in total height, and a C-5 can only carry cargo that is up to 13.5ft in height.  Even the An-225, the largest cargo aircraft in the world, can only carry cargo that is up to 14ft in height.

So SLS-sized payloads will have to be built close to water transportation, which limits using existing facilities.  But even those existing facilities would have to create new infrastructure and tooling to handing SLS-sized payload manufacturing and testing.  Sure we have built rockets of that size before, but not payloads.

So there are costs associated with setting up a factory that has to be absorbed by the first product that is produced.  If more are produced the average costs can go down, but if we're talking about a single replacement for the Hubble, then the costs of building an HLV-sized monolithic platform could be very considerable.

Keep in mind, Ron, 8 meter monolithic telescope mirrors are cast and polished in Phoenix, Arizona, under the University of Arizona football stadium.  There's no water transport there.  These mirrors, fragile as they may seem, are placed in containers for transport, and are taken on public roads to remote mountaintops where they are surrounded by clean facilities that allow for their maintenance.


It's hard to believe that NASA can't afford the scale of facilities that other observatories, which are also operating on shoestring budgets, manage to provide.

The Steward Observatory Mirror Lab, where the GMT and LSST mirrors are being manufactured, is in Tucson, not Phoenix. Also, since those mirrors are shipped in the horizontal position, all you need is a wide road, no serious constraints on height.

[jg]

And big mirrors have been shipped elsewhere in the world...  No particular thermal problems doing so.  And the mirrors are only in a really clean environment for aluminization.  Big telescopes have open truss supports.

[Coastal Ron]

Keep in mind, Ron, 8 meter monolithic telescope mirrors are cast and polished in Phoenix, Arizona, under the University of Arizona football stadium.  There's no water transport there.  These mirrors, fragile as they may seem, are placed in containers for transport, and are taken on public roads to remote mountaintops where they are surrounded by clean facilities that allow for their maintenance.

The Steward Observatory Mirror Lab, where the GMT and LSST mirrors are being manufactured, is in Tucson, not Phoenix. Also, since those mirrors are shipped in the horizontal position, all you need is a wide road, no serious constraints on height.

Thanks for pointing that out, and I was trying to highlight that point when I only referenced height restrictions, not width restrictions.  I guess I was too subtle.

While a component could be built anywhere and moved anywhere, the larger subassemblies and full up assemblies would likely be impacted by height restrictions.  Unless everyone is thinking the Hubble 2.0 is going to be less than 5m in length while being 8m in diameter...

[Coastal Ron]

It's hard to believe that NASA can't afford the scale of facilities that other observatories, which are also operating on shoestring budgets, manage to provide.

Operating in space requires different designs and materials, and the inability to access the instrument every day for solving minor problems means you have to spend a lot of time and money on making the instrument very dependable.

For instance, if a computer goes out on an observatory here on Earth you have a tech replace it that same day.  What are your options if that happens in space?  Well you don't want that to happen, so you spend $Millions on making very dependable computers.

Big difference.

[AnalogMan]

Concepts for a large space telescope assembled in stages are being thought about by some groups.  For example Northrop Grumman are studying an Evolved Space Telescope:

• 14m to 20m aperture
• three stage build
• initial stage & each increment forms a complete operational telescope
• 3-5 years between stage launches

A couple of recent 2-pagers from a COPAG call for white papers and a short AAS presentation are attached.  Rather light on any practical details other than telescope performance.

(COPAG = Cosmic Origins Program Analysis Group)

[Mr. D]

Concepts for a large space telescope assembled in stages are being thought about by some groups.  For example Northrop Grumman are studying an Evolved Space Telescope:

• 14m to 20m aperture
• three stage build
• initial stage & each increment forms a complete operational telescope
• 3-5 years between stage launches

A couple of recent 2-pagers from a COPAG call for white papers and a short AAS presentation are attached.  Rather light on any practical details other than telescope performance.

(COPAG = Cosmic Origins Program Analysis Group)

None of that includes a cost estimate, which should be a huge red flag. This all needs to fit in the Astrophysics theme's budget, and pass a Decadal Survey, so the cost is absolutely critical. A 20 m telescope on the ground is in the 1 G$ region, I'll decline to guess how much that would be in space.

Besides, if they actually intend to get the extra mirrors to be phased up (aligned coherently) with the rest, the initial instruments will either need to massively oversample the PSF in the early phases, or they'll need to be changed at each upgrade. Unless they just want to get them in an incoherent configuration, but why would anyone do that?

[Stormbringer]

DARPA gets in on the action:

http://www.spacedaily.com/reports/Brainstorm_with_DARPA_on_a_100x_Zoom_Lens_for_Seeing_Distant_Space_Objects_More_Clearly_999.html

[Star One]

DARPA gets in on the action:

http://www.spacedaily.com/reports/Brainstorm_with_DARPA_on_a_100x_Zoom_Lens_for_Seeing_Distant_Space_Objects_More_Clearly_999.html

That's a specific solution for a ground based telescope.

[Stormbringer]

i bet it will have benefits for spaceborne technology too

it should advance the state of the art.

[Star One]

Here's a follow on article from Ted Molczan to the one I linked to in my OP with further educated speculation.

http://www.satobs.org/seesat/May-2015/0096.html

[Burninate]

On the topic of (currently) 1.1m aperture non-astronomical space telescopes,

From Twitter:  < pbdes> [c0] DigitalGlobe CEO Tarr: Our next-gen sats to be much less costly per unit than our current sats, which are ~$750M apiece inc launch/insure.

[Mr. D]

On the topic of (currently) 1.1m aperture non-astronomical space telescopes,

From Twitter:  < pbdes> [c0] DigitalGlobe CEO Tarr: Our next-gen sats to be much less costly per unit than our current sats, which are ~$750M apiece inc launch/insure.

Well, Kepler cost 600M$ (FY 2009) for a 0.95m schmidt camera with a 1.4m primary. Gaia cost about 740Meuros (FY2013) for 2x 1.45x0.5m telescopes. Modest aperture astronomical space telescopes with simple(-ish in the case of Gaia) instruments can be done in a manageable budget.

Large aperture space telescopes with a generalist array of instruments is another matter entirely.