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Why is this better than launching a telescope into orbit?

by zxcb1 7y ago

madaxe_again 7y ago
Mass - cost-benefit still means ground based telescopes are the best option for most scenarios. The protests may change that equation. As much as I’m automatically inclined to side with science over mysticism, there are other telescopes being built right now (ELT, GMT) in the same class, both in Chile, where the mountains aren’t sacred, but just mountains. So - while they’re pushing on for now, it seems there’s as much dogma (we must have this telescope here) amongst scientists as their is amongst the spiritualists - yes, the top of Hawaii is a uniquely good spot for a telescope - within US borders - there are other spots just as good, however, but those would require international negotiation and cooperation rather than just domestic negotiation and cooperation. It all comes down to cost/benefit, and I think it’s getting marginal for the TMT. They’re going to need round the clock security, as the protests won’t stop once it’s built. It’s not too late to build it elsewhere - even in space. Launch costs have dropped dramatically since the TMT was conceived, and are continuing to do so. Assembly will then be the tricky part, as with JWST.
- zxcb1 7y ago
  Thanks. So what kind of improvements do they expect with this one?
  - pas 7y ago
    It's planned as a general purpose observatory. Bigger mirror than any ever used would allow sharper, better images.
    - madaxe_again 7y ago
      The ELT will be complete five years before the TMT, and has a forty meter aperture.
      - wumms 7y ago
        First light: ELT 2025 (39.3m, 978m²) TMT 2027 (30m, 655m²) (Future first-light dates are provisional and likely to change. https://en.wikipedia.org/wiki/Extremely_Large_Telescope https://en.wikipedia.org/wiki/Extremely_Large_Telescope) Nice mirror size comparison: https://en.wikipedia.org/wiki/Extremely_Large_Telescope#/media/File:Comparison_optical_telescope_primary_mirrors.svg https://en.wikipedia.org/wiki/Extremely_Large_Telescope#/med...
      - _ph_ 7y ago
        As a telescope, the ELT will be superior, but it is in the other hemisphere. So the TMT does not only give more observation "bandwidth", but also unlocks a high quality view into the northern hemisphere. Together, those two telescopes can cover the whole sky.
    - zxcb1 7y ago
      Ok. So a space telescope would be prefered and this is the second best option, limited by budget?
      - madaxe_again 7y ago
        Absolutely. The cost, even with current cheapening launch costs, would still be astounding. As long as we’re using chemical rockets fuelled from earth we are going to be really limited in terms of what we can put in space - and again, assembly - we couldn’t even get Hubble right first time, and it has taken thousands of hours of spacewalks to keep operating. It’s totally been worth it though. Stepping stones - if the new class of earth based telescopes finds something worth looking at, there will be space telescopes that make the JWST look like a toy - but not for a while yet. This is basically the “cheap” trial experiment.
        dogsgobork 7y ago
        > it has taken thousands of hours of spacewalks to keep operating. The total eva time for all five servicing missions for Hubble is under 200 hours.
      - Cthulhu_ 7y ago
        Budget and maintainability - I mean the Hubble telescope only managed to stay in operation for as long as it did thanks to a number of maintenance missions via the Space Shuttle. That extended its lifetime by a considerable margin. Meanwhile, this observatory will be much more easily accessible and will therefore have a lifetime many times that of the Hubble - and can become a museum after its lifetime.
  - sq_ 7y ago
    The larger the mirror of the telescope, the more light it can gather from a given source. The expanded light-gathering capability of a thirty meter aperture combined with the great conditions that exist at the top of Mauna Kea because of its altitudes will allow for a lot of observations that would've been impossible before because the data produced wouldn't have been clear enough.
  - madaxe_again 7y ago
    That’s actually a better question than you think. The answer is “we don’t know”. The light gathering power will be greater than any current instrument. The spatial resolution will be better than any current non-interferometric system. The adaptive optics are in a new league, and the mirror coatings will allow a very broad spectrum to be sensed. But what will we discover? We honestly don’t know. It’s been a bit of a bone of contention as many in science would argue that you should define your goals and then devise the experiment and apparatus - but cosmology and astronomy are a bit different, as most of the huge discoveries have been utterly unexpected, and have “just happened” as a result of better telescopes and observations, from moons of other planets to heliocentricism to other galaxies to red shift to the Big Bang to quasars and pulsars - we didn’t expect any of these things, we just found them. So that’s the improvement - hopefully new science, new discoveries.
- goodcanadian 7y ago
  They’re going to need round the clock security, as the protests won’t stop once it’s built. I'm a bit skeptical of this particular claim as the existing telescopes haven't needed round the clock security. Generally speaking, I never felt the telescopes were as controversial as is made out. Rather, the opposition is a small, but very vocal minority. That said, I can see why TMT is particularly contentious as any new construction is an obvious point of resistance, and TMT is so much larger than the existing telescopes.
- mjsweet 7y ago
  Bear in mind that Mauna Kea is only one of two excellent locations in the northern hemisphere... the other being Gran Canarias in the Atlantic. Chile is equally as good as Hawaii with stable ocean air and dry conditions making for fantastic seeing conditions, but it covers a very different part of the night sky down south. I can’t imagine UH doing what the protectors are asking and simply plonk the TMT in a completely different ocean. TMT is the only planned 30m class telescope in the northern hemisphere at the moment. Longitudinal placement is also important for tracking transient phenomena such as FRB’s and NEO’s. this is why Hawaii is such a critical location for doing optical observations. I would not be surprised if the Chinese build a thirty meter class telescope at some stage. Not sure where though?
  - walrus01 7y ago
    I'm no telescope expert, but wouldn't somewhere high in the mountains near Leh, India also be suitable? Or near Skardu, Pakistan? https://en.wikipedia.org/wiki/Skardu https://en.wikipedia.org/wiki/Skardu On the high Tibetan plateau somewhere not very far from this airport? https://en.wikipedia.org/wiki/Qamdo_Bamda_Airport https://en.wikipedia.org/wiki/Qamdo_Bamda_Airport
    - mkl 7y ago
      China has lots of mountains and desert, so I don't think locations are a problem. There have been people-based problems though: https://www.wired.com/story/china-fast-worlds-largest-telescope-tourists/ https://www.wired.com/story/china-fast-worlds-largest-telesc...
    - PopePompus 7y ago
      Mountains within large mountain ranges are not as good as a (relatively) isolated peak like Mauna Kea. An isolated peak can have something resembling laminar flow of the air over the summit, resulting in good "seeing", whilst a peak within a large range has a more turbulent air flow above it.
      - GlennS 7y ago
ajross 7y ago
Because you can reach the summit of Mauna Kea with a RAV4 and not a Falcon Heavy.
- HeWhoLurksLate 7y ago
  I'm pretty sure that we can reach Mauna Kea with a Falcon Heavy, too.
  - 420codebro 7y ago
    We aren’t talking about ICBMs, dog.
  - RandomBacon 7y ago
    We've already reached space with a Tesla Roadster, I'm sure a Toyota RAV4 wouldn't be much different. It sure is a lot cheaper to go to Mauna Kea than space though. /joke
mikeash 7y ago
It’s pretty hard to launch a thirty meter mirror into orbit.
rtkwe 7y ago
It's easier to build and modify a telescope on the ground. Once a telescope is launched it's extremely expensive to go make any changes to it, on the ground new experiments can be added later. Currently we have no way of doing a Hubble style modification even if we could get to the satellites (JWST is going to be launched very far out for example) that was something pretty unique to the Shuttle program. On top of that building a telescope with a very large mirror is much harder because they have to be launched. The mirror on James Webb is only 6.5m (ish) and it requires a folding mechanism to fit inside the faring of rockets. Making a 30m mirror may not be possible without going to farings larger than any rocket around today. BFR if it actually pans out will make much larger space telescopes possible.
petascale 7y ago
Because for a given amount of funding and engineering effort, a telescope on the ground can be a lot larger. Hubble has a 2.4 meter mirror, TMT is 30 meters. Resolution scales with the diameter of the mirror (so an order of magnitude more for TMT), while light gathering scales with the area (two orders of magnitude more for TMT). Traditionally, there were two challenges for large ground based telescopes: a) We couldn't make telescope mirrors larger than ~5 meters because the glass starts to deform under its own weight and the view gets worse rather than better; and b) we lose too much to atmospheric distortion. The solution to the first issue is to assemble large mirrors from many small mirrors in a honeycomb pattern[0]. The solution to the second one is adaptive optics[1]: Actuators and computer control can compensate for atmospheric distortion by precisely deforming the mirror in real time, several times per second, to cancel out the distortion. We still need a good location for the telescope to minimize the amount of distortion we need to handle, but with that we could for the first time achieve better resolution from the ground with the 10-meter Keck. These days the benefits of a space telescope come not so much from visible light, but from other wavelengths that are fully or partially blocked by the atmosphere[2]. Like UV, X-ray, or infrared like the upcoming James Webb space telescope. [0] https://www.wired.com/2008/10/in-the-late-197/ https://www.wired.com/2008/10/in-the-late-197/ [1] https://en.wikipedia.org/wiki/Adaptive_optics https://en.wikipedia.org/wiki/Adaptive_optics [2] http://gsp.humboldt.edu/OLM/Courses/GSP_216_Online/lesson2-1/atmosphere.html http://gsp.humboldt.edu/OLM/Courses/GSP_216_Online/lesson2-1...
Rebelgecko 7y ago
A service call for Hubble cost more than a hundred million dollars. A service call in Hawaii would probably cost a few thousand. When you build something to go to space it gets way more expensive. Hubble cost around $4billion before it launched, JWST is gonna cost more than $10b, and WFIRST, a relatively cheap space telescope, will cost at least $3 billion. The most expensive telescope on Earth only cost about $1 billion. It weights about 15 million pounds, so just the launch costs to put it in orbit would exceed the $1 billion it cost to build.

Why is this better than launching a telescope into orbit?

by zxcb1 7y ago

Why is this better than launching a telescope into orbit?

Mass - cost-benefit still means ground based telescopes are the best option for most scenarios. The protests may change that equation. As much as I’m automatically inclined to side with science over mysticism, there are other telescopes being built right now (ELT, GMT) in the same class, both in Chile, where the mountains aren’t sacred, but just mountains. So - while they’re pushing on for now, it seems there’s as much dogma (we must have this telescope here) amongst scientists as their is amongst the spiritualists - yes, the top of Hawaii is a uniquely good spot for a telescope - within US borders - there are other spots just as good, however, but those would require international negotiation and cooperation rather than just domestic negotiation and cooperation. It all comes down to cost/benefit, and I think it’s getting marginal for the TMT. They’re going to need round the clock security, as the protests won’t stop once it’s built. It’s not too late to build it elsewhere - even in space. Launch costs have dropped dramatically since the TMT was conceived, and are continuing to do so. Assembly will then be the tricky part, as with JWST.

zxcb1 7y ago
Thanks. So what kind of improvements do they expect with this one?
- pas 7y ago
  It's planned as a general purpose observatory. Bigger mirror than any ever used would allow sharper, better images.
  - madaxe_again 7y ago
    The ELT will be complete five years before the TMT, and has a forty meter aperture.
    - wumms 7y ago
      First light: ELT 2025 (39.3m, 978m²) TMT 2027 (30m, 655m²) (Future first-light dates are provisional and likely to change. https://en.wikipedia.org/wiki/Extremely_Large_Telescope https://en.wikipedia.org/wiki/Extremely_Large_Telescope) Nice mirror size comparison: https://en.wikipedia.org/wiki/Extremely_Large_Telescope#/media/File:Comparison_optical_telescope_primary_mirrors.svg https://en.wikipedia.org/wiki/Extremely_Large_Telescope#/med...
    - _ph_ 7y ago
      As a telescope, the ELT will be superior, but it is in the other hemisphere. So the TMT does not only give more observation "bandwidth", but also unlocks a high quality view into the northern hemisphere. Together, those two telescopes can cover the whole sky.
  - zxcb1 7y ago
    Ok. So a space telescope would be prefered and this is the second best option, limited by budget?
    - madaxe_again 7y ago
      Absolutely. The cost, even with current cheapening launch costs, would still be astounding. As long as we’re using chemical rockets fuelled from earth we are going to be really limited in terms of what we can put in space - and again, assembly - we couldn’t even get Hubble right first time, and it has taken thousands of hours of spacewalks to keep operating. It’s totally been worth it though. Stepping stones - if the new class of earth based telescopes finds something worth looking at, there will be space telescopes that make the JWST look like a toy - but not for a while yet. This is basically the “cheap” trial experiment.
      - dogsgobork 7y ago
        > it has taken thousands of hours of spacewalks to keep operating. The total eva time for all five servicing missions for Hubble is under 200 hours.
    - Cthulhu_ 7y ago
      Budget and maintainability - I mean the Hubble telescope only managed to stay in operation for as long as it did thanks to a number of maintenance missions via the Space Shuttle. That extended its lifetime by a considerable margin. Meanwhile, this observatory will be much more easily accessible and will therefore have a lifetime many times that of the Hubble - and can become a museum after its lifetime.
- sq_ 7y ago
  The larger the mirror of the telescope, the more light it can gather from a given source. The expanded light-gathering capability of a thirty meter aperture combined with the great conditions that exist at the top of Mauna Kea because of its altitudes will allow for a lot of observations that would've been impossible before because the data produced wouldn't have been clear enough.
- madaxe_again 7y ago
  That’s actually a better question than you think. The answer is “we don’t know”. The light gathering power will be greater than any current instrument. The spatial resolution will be better than any current non-interferometric system. The adaptive optics are in a new league, and the mirror coatings will allow a very broad spectrum to be sensed. But what will we discover? We honestly don’t know. It’s been a bit of a bone of contention as many in science would argue that you should define your goals and then devise the experiment and apparatus - but cosmology and astronomy are a bit different, as most of the huge discoveries have been utterly unexpected, and have “just happened” as a result of better telescopes and observations, from moons of other planets to heliocentricism to other galaxies to red shift to the Big Bang to quasars and pulsars - we didn’t expect any of these things, we just found them. So that’s the improvement - hopefully new science, new discoveries.
goodcanadian 7y ago
They’re going to need round the clock security, as the protests won’t stop once it’s built. I'm a bit skeptical of this particular claim as the existing telescopes haven't needed round the clock security. Generally speaking, I never felt the telescopes were as controversial as is made out. Rather, the opposition is a small, but very vocal minority. That said, I can see why TMT is particularly contentious as any new construction is an obvious point of resistance, and TMT is so much larger than the existing telescopes.
mjsweet 7y ago
Bear in mind that Mauna Kea is only one of two excellent locations in the northern hemisphere... the other being Gran Canarias in the Atlantic. Chile is equally as good as Hawaii with stable ocean air and dry conditions making for fantastic seeing conditions, but it covers a very different part of the night sky down south. I can’t imagine UH doing what the protectors are asking and simply plonk the TMT in a completely different ocean. TMT is the only planned 30m class telescope in the northern hemisphere at the moment. Longitudinal placement is also important for tracking transient phenomena such as FRB’s and NEO’s. this is why Hawaii is such a critical location for doing optical observations. I would not be surprised if the Chinese build a thirty meter class telescope at some stage. Not sure where though?
- walrus01 7y ago
  I'm no telescope expert, but wouldn't somewhere high in the mountains near Leh, India also be suitable? Or near Skardu, Pakistan? https://en.wikipedia.org/wiki/Skardu https://en.wikipedia.org/wiki/Skardu On the high Tibetan plateau somewhere not very far from this airport? https://en.wikipedia.org/wiki/Qamdo_Bamda_Airport https://en.wikipedia.org/wiki/Qamdo_Bamda_Airport
  - mkl 7y ago
    China has lots of mountains and desert, so I don't think locations are a problem. There have been people-based problems though: https://www.wired.com/story/china-fast-worlds-largest-telescope-tourists/ https://www.wired.com/story/china-fast-worlds-largest-telesc...
  - PopePompus 7y ago
    Mountains within large mountain ranges are not as good as a (relatively) isolated peak like Mauna Kea. An isolated peak can have something resembling laminar flow of the air over the summit, resulting in good "seeing", whilst a peak within a large range has a more turbulent air flow above it.
    - GlennS 7y ago

ajross 7y ago

Because you can reach the summit of Mauna Kea with a RAV4 and not a Falcon Heavy.

HeWhoLurksLate 7y ago
I'm pretty sure that we can reach Mauna Kea with a Falcon Heavy, too.
- 420codebro 7y ago
  We aren’t talking about ICBMs, dog.
- RandomBacon 7y ago
  We've already reached space with a Tesla Roadster, I'm sure a Toyota RAV4 wouldn't be much different. It sure is a lot cheaper to go to Mauna Kea than space though. /joke

mikeash 7y ago

It’s pretty hard to launch a thirty meter mirror into orbit.

rtkwe 7y ago

It's easier to build and modify a telescope on the ground. Once a telescope is launched it's extremely expensive to go make any changes to it, on the ground new experiments can be added later. Currently we have no way of doing a Hubble style modification even if we could get to the satellites (JWST is going to be launched very far out for example) that was something pretty unique to the Shuttle program. On top of that building a telescope with a very large mirror is much harder because they have to be launched. The mirror on James Webb is only 6.5m (ish) and it requires a folding mechanism to fit inside the faring of rockets. Making a 30m mirror may not be possible without going to farings larger than any rocket around today. BFR if it actually pans out will make much larger space telescopes possible.

petascale 7y ago

Because for a given amount of funding and engineering effort, a telescope on the ground can be a lot larger. Hubble has a 2.4 meter mirror, TMT is 30 meters. Resolution scales with the diameter of the mirror (so an order of magnitude more for TMT), while light gathering scales with the area (two orders of magnitude more for TMT). Traditionally, there were two challenges for large ground based telescopes: a) We couldn't make telescope mirrors larger than ~5 meters because the glass starts to deform under its own weight and the view gets worse rather than better; and b) we lose too much to atmospheric distortion. The solution to the first issue is to assemble large mirrors from many small mirrors in a honeycomb pattern[0]. The solution to the second one is adaptive optics[1]: Actuators and computer control can compensate for atmospheric distortion by precisely deforming the mirror in real time, several times per second, to cancel out the distortion. We still need a good location for the telescope to minimize the amount of distortion we need to handle, but with that we could for the first time achieve better resolution from the ground with the 10-meter Keck. These days the benefits of a space telescope come not so much from visible light, but from other wavelengths that are fully or partially blocked by the atmosphere[2]. Like UV, X-ray, or infrared like the upcoming James Webb space telescope. [0] https://www.wired.com/2008/10/in-the-late-197/ https://www.wired.com/2008/10/in-the-late-197/ [1] https://en.wikipedia.org/wiki/Adaptive_optics https://en.wikipedia.org/wiki/Adaptive_optics [2] http://gsp.humboldt.edu/OLM/Courses/GSP_216_Online/lesson2-1/atmosphere.html http://gsp.humboldt.edu/OLM/Courses/GSP_216_Online/lesson2-1...

Rebelgecko 7y ago

A service call for Hubble cost more than a hundred million dollars. A service call in Hawaii would probably cost a few thousand. When you build something to go to space it gets way more expensive. Hubble cost around $4billion before it launched, JWST is gonna cost more than $10b, and WFIRST, a relatively cheap space telescope, will cost at least $3 billion. The most expensive telescope on Earth only cost about $1 billion. It weights about 15 million pounds, so just the launch costs to put it in orbit would exceed the $1 billion it cost to build.