The European Southern Observatory (ESO) has been able to capture telescopic images at visible wavelengths from the ground that are sharper than those from the NASA/ESA Hubble Space Telescope. The ground-based Very Large Telescope (VLT) has used an adaptive optics mode called laser tomography to capture images of distant objects in the solar system. The laser tomagraphy compensates for atmospheric turbulence resulting in more detail than anything prior. It works by stimulating sodium ions in the upper atmosphere using two pairs of lasers to calculate the turbulence and adjusting a deformable secondary mirror thousands of times per second in response.
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Laser Tomography Adaptive Optics Enable Sharper Telescopic Imaging
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(Score: 4, Interesting) by takyon on Friday July 27 2018, @05:04PM
I didn't read the original ESO release when I first saw this story, so it wasn't clear to me that the VLT's adaptive optics image of Neptune exceeded Hubble's quality. But they explicitly state that it is sharper. And this is first light for this laser tomography mode.
So right off the bat, we could come up with a list of objects for which the best available image was taken by Hubble (no flybys yet), and the VLT could be able to take a better picture (although Hubble covers more wavelengths so this might not be true in all cases).
Pallas [wikipedia.org]: https://en.wikipedia.org/wiki/File:PallasHST2007.jpg [wikipedia.org]
Eris [wikipedia.org]: https://en.wikipedia.org/wiki/File:Eris_and_dysnomia2.jpg [wikipedia.org]
Makemake [wikipedia.org]: https://en.wikipedia.org/wiki/File:Makemake_with_moon.JPG [wikipedia.org]
2007 OR10 [wikipedia.org]: https://en.wikipedia.org/wiki/File:2007_OR10_and_its_moon.png [wikipedia.org]
Haumea [wikipedia.org] (this image is from Keck): https://en.wikipedia.org/wiki/File:2003_EL61_Haumea,_with_moons.jpg [wikipedia.org]
Quaoar [wikipedia.org]: https://en.wikipedia.org/wiki/File:Quaoar_PRC2002-17e.jpg [wikipedia.org]
Sedna [wikipedia.org]: https://en.wikipedia.org/wiki/File:Sedna_PRC2004-14d.jpg [wikipedia.org]
Salacia [wikipedia.org]: https://en.wikipedia.org/wiki/File:Salacia_Hubble.png [wikipedia.org]
2002 UX25 [wikipedia.org]: https://en.wikipedia.org/wiki/File:20131105_2002_UX25_hst.png [wikipedia.org]
... and so on.
Hubble observations have also been used to observe plumes emitted by Europa [soylentnews.org].
As the release notes, this is a test of the technology ahead of its use with the Extremely Large Telescope [wikipedia.org], which will be able to produce much sharper images than Hubble.
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(Score: 3, Interesting) by datapharmer on Friday July 27 2018, @07:14PM (1 child)
Hrm... reminds me of the fluidcam story from a few days back. I wonder if the correction could be done in software instead of having a deforming mirror, which could enable existing telescopes to get a few of these lasers and greatly improve their eyesight.
(Score: 1, Interesting) by Anonymous Coward on Friday July 27 2018, @08:06PM
Generally, no. If you have sufficiently high signal-to-noise (i.e., a bright scene) and you can thus use sufficiently short exposure times that freeze the atmospheric turbulence, then there are algorithms you can do to correct it (if your aperture is small enough, you don't have to correct for it because the image will be in focus, but laterally shifted on your camera; if your aperture is large enough, you can correct for it but you need additional instrumentation to measure it (e.g., a Shack-Hartmann sensor)).
This issue you have is these telescopes need to use long exposure times were the atmosphere randomly moves the image around on your camera that averages out to a Gaussian smear. You need the deformable mirror to hold an in-focus image on the same pixels during the exposure. Besides, if you are going through the process of adding several of these lasers and detectors to measure the wavefronts of the light coming down to the ground, the deformable mirror actually isn't the driving cost. These mirrors are generally not very large.
(Score: 3, Touché) by bzipitidoo on Friday July 27 2018, @07:24PM (3 children)
Hubble is over 25 years old. Tough for tech to not become obsolete in so many ways over such a period.
Adaptive optics has been around for a while now, but I hadn't heard it was this good. Sounds like the case for space based telescopes got a lot harder. Is James Webb still worth deploying in space?
(Score: 2) by takyon on Friday July 27 2018, @07:30PM (1 child)
At some point, making a big ground-based optical telescope poses engineering challenges that might not be experienced in space, where a design could unfold, be made of an ultra-thin material that might not work on the ground where there is wind, or be built with modular mirrors and multiple launches if necessary.
Kilometer Space Telescope (KST) [nasa.gov]
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(Score: 0) by Anonymous Coward on Friday July 27 2018, @07:45PM
Plus, ground-based telescopes can only see what is in the skies above them, so to get decent galactic coverage, you need multiple telescopes across multiple latitudes. And ground-based telescopes can only see the wavelengths that make it through the atmosphere.
(Score: 1, Informative) by Anonymous Coward on Saturday July 28 2018, @07:13AM
JWST is primarily an infrared telescope. Earth's atmosphere attenuates the wavelengths JWST is focused on [sic].
The infrared design is to help image distant objects whose light has been red-shifted that much due to their distance.
(Score: 2) by cellocgw on Friday July 27 2018, @09:56PM
Former long-time AO system designer & developer here -- Great to see the extension of the LaserGuide Star (one such laser beacon) being extended to improve estimation of the atmospheric turbulence. This is great stuff.
Physicist, cellist, former OTTer (1190) resume: https://app.box.com/witthoftresume
(Score: 2) by takyon on Friday July 27 2018, @10:06PM
Uranus and Neptune Are Potential Targets for 2030s Missions [soylentnews.org]
I'm glad they chose Neptune as their first target. We need to follow-up on Voyager 2 already.
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(Score: 2) by hendrikboom on Friday July 27 2018, @10:30PM
Just Wow! OK?
(Score: 1) by Coward, Anonymous on Saturday July 28 2018, @12:10AM (5 children)
TFA says in the main text that the ESO images have "comparable" sharpness to Hubble. The figure caption, which was used for TFS, says "sharper". Which is it? If you look at the comparison photo [eso.org], in the ESO picture, Neptune is not really round. So maybe "sharpness" only tells part of the story. NASA can hire artists to fabricate missing details in a "sharp" way, too.
(Score: 2) by takyon on Saturday July 28 2018, @12:33AM (4 children)
Explicit enough to me.
From the image comparison page:
Comparable as in, here's the same planet, at roughly the same angle, with the sizes matching (resized if necessary).
Other shape wonkiness can be ascribed to how the instruments work, or differing position of Neptune.
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(Score: 1) by Coward, Anonymous on Saturday July 28 2018, @03:34AM (3 children)
From TFA:
[emphasis mine]
(Score: 3, Informative) by takyon on Saturday July 28 2018, @03:52AM (2 children)
I'm leaning towards sharper, but not by much. It would be great to have it quantified rather than have vague statements.
This could be considered a dress rehearsal for the Extremely Large Telescope [wikipedia.org], which will be 16 times sharper than Hubble. That's a difference that is impossible to ignore. The Giant Magellan Telescope [wikipedia.org] is planned to be 10 times sharper than Hubble and will also use a laser tomography adaptive optics system [gmto.org].
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(Score: 1) by Coward, Anonymous on Saturday July 28 2018, @05:37PM (1 child)
The Large Binocular Telescope announced 3x sharper than Hubble [www.mpg.de] imaging in 2010 with 10x sharper seemingly just around the corner. Where are the resulting astronomy papers? [stsci.edu]
(Score: 2) by takyon on Saturday July 28 2018, @05:58PM
https://en.wikipedia.org/wiki/Large_Binocular_Telescope [wikipedia.org]
Maybe sharp is still shit for ground telescopes. One of Hubble's major advantages is its infrared capability. That's what allows it to observe highly redshifted objects.
Hubble Team Breaks Cosmic Distance Record [nasa.gov]
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