[HN Gopher] Sky-scanning complete for Gaia
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Sky-scanning complete for Gaia
Author : sohkamyung
Score : 129 points
Date : 2025-01-15 09:43 UTC (13 hours ago)
(HTM) web link (www.esa.int)
(TXT) w3m dump (www.esa.int)
| qwertox wrote:
| You may want to know: the high-res images which are offered for
| downloading contain the same image which is shown on the page,
| that is, the infographic.
|
| Not worth the download, as I thought that it would contain a huge
| panorama of the sky.
| robin_reala wrote:
| The downlinked data is claimed to be 142TB compressed. I
| suspect that the huge panorama might be a little big for your
| computer.
| IndrekR wrote:
| For real data you can use Gaia ESA archive:
| https://gea.esac.esa.int/archive/
|
| I went to study MSc in Space Science and Technology as a hobby
| few years ago. In one course (2022) we had an assignment to
| find Supernovae from recent Gaia data (Python code). Then made
| sure this is observable by University's robotic telescope (and
| compliant with local weather forecast). Next requested the
| observation from the telescope and if successful, received the
| pictures next day. Had to analyse the results as well. It
| surprised me how much data there actually is available in quite
| open format from ESA missions.
|
| Controlling remote telescope few thousand kilometres away was
| also a nice experience.
| boxed wrote:
| I wonder if it could keep giving us useful data without the
| precision rotation? Intuitively it seems like we should be able
| to figure out where it's pointing by star-matching plus dead
| reckoning based on the last frame.
| ndileas wrote:
| It's possible...but the point of this instrument is to measure
| star locations very precisely. It probably has a star tracker
| for positioning doing what you're suggesting. If you were to
| use that type of positioning info you could introduce
| inaccuracies into the measured data eventually.
|
| Also, every mission comes to an end eventually - better to do
| it in the right way and have the right amount of propellent
| saved for either a graveyard orbit or de-orbiting. It met the
| mission timeline and goals.
| boxed wrote:
| Yea ok. Still, it seems like it could produce a lot of very
| useful data if switched to a blind spinning mode.
| gmiller123456 wrote:
| The current coordinate system is based on extremely distant
| radio sources. Ground based scopes found some bright galactic
| sources which GAIA aligned to, and is measuring everything
| relative to those. And now GAIA is the defining source of the
| ICRS for optical observations.
| NKosmatos wrote:
| Direct link to some very very nice images and animations:
| https://www.esa.int/Science_Exploration/Space_Science/Gaia
|
| Two of my favorites:
| https://www.esa.int/ESA_Multimedia/Images/2025/The_best_Milk...
|
| https://www.esa.int/ESA_Multimedia/Images/2025/01/The_best_M...
| dylan604 wrote:
| I get how Gaia could make the best edge on image, but how could
| Gaia (or anything man made) get the the "best" face on image?
| iAmAPencilYo wrote:
| All of these are "Artist's Impressions". My best guess is
| they run a simulation based on the data from the spacecraft
| and then can pan the camera around as they see fit
| BizarroLand wrote:
| From the page:
|
| [Image Description: A model image of what our home galaxy,
| the Milky Way, might look like edge-on, against a pitch-
| black backdrop. The Milky Way's disc appears in the centre
| of the image, as a thin, dark-brown line spanning from left
| to right, with the hint of a wave in it. The line appears
| to be etched into a thin glowing layer of silver sand, that
| makes it look as if it was drawn with a coloured pencil on
| coarse paper. The bulge of the galaxy sits like a glowing,
| see-through pearl in the shape of a sphere in the centre of
| this brown line.]
| dylan604 wrote:
| "The best Milky Way map, by Gaia (edge-on)"
|
| The "by Gaia" implies the opposite to me. Unless the
| "artist's impressions" are from someone named Gaia???
| goodcanadian wrote:
| The whole purpose of Gaia is to precisely measure the
| position of stars (and other objects). Once positions are
| known, a 3D model can be built. But how are the distances
| measured? The answer is parallax, essentially triangulation.
| You look for very small changes of position against the
| background sky. You use the width of the earth's orbit as the
| baseline and measure at different times of the year.
| tokai wrote:
| And now to use the data to make the most realistic scifi game.
| With correct stellar motion during relativistic travel.
| flohofwoe wrote:
| Elite Dangerous already has more known star systems (160k) in
| the Milky Way than you can realistically visit - and the rest
| (400 billion) filled in with plausibly simulated systems:
| https://elite-dangerous.fandom.com/wiki/Galaxy#Milky_Way - it
| even kind-of predicted a star system that was only discovered
| after the game was released: https://elite-
| dangerous.fandom.com/wiki/Trappist-1#Impact_of...
| buildbot wrote:
| I didn't realize a game actually used an approach like this,
| really cool. Reminds me of the simulated MMORG world in Neal
| Stephenson's README, where they tried to simulate the
| formation of the planet to get realistic mineral deposits and
| topology.
| vimax wrote:
| REAMDE
| buildbot wrote:
| Oops, thanks!
| NetOpWibby wrote:
| I just looked this up, sounds like a fantastic read. I'll
| add it to my backlog.
| PittleyDunkin wrote:
| I really wish they would have identified Gaia as some kind of
| satellite. Gaia is also a name for Earth itself.
| marcodiego wrote:
| IIRC Gaia had a performance degradation because of stray light,
| probably ice on the border of it's aperture[1].
|
| How has that affected this result?
|
| [1] https://blogs.esa.int/gaia/2014/06/16/preliminary-
| analysis-o...
| sega_sai wrote:
| It was not ice, but fibers from the sun shield. The ice issue
| was resolved by heating the satellite. The stray light issue
| affected spectra measurements, but not the astrometric side of
| the mission
| ndileas1 wrote:
| Now that most stars are mapped, next step: map all the planets.
| mrbluecoat wrote:
| Farewell, friend. Hello, LSST.
| lysace wrote:
| Gaia has a _1.0 x 0.5 m focal plane array on which light from
| both telescopes is projected. This in turn consists of 106 CCDs
| of 4500 x 1966 pixels each, for a total of 937.8 megapixels._
|
| Neat.
| perihelions wrote:
| The really neat part is the instrument precision. It's
| terrifyingly good and I have no idea how it (really) works.
|
| - _" Gaia measures their positions to an accuracy of 24
| microarcseconds, comparable to measuring the diameter of a
| human hair at a distance of 1000 km"_
|
| https://www.esa.int/Science_Exploration/Space_Science/Gaia/C...
| colechristensen wrote:
| Isn't that just the distance between pixels and the image
| projected onto them?
| perihelions wrote:
| No: it's far weirder and I'm not knowledgeable enough to
| explain it.
| echoangle wrote:
| Probably not. The accuracy with which you know the pointing
| of the telescope probably also plays into it (unless the
| FOV is large enough to have other stars as a reference?),
| and you can do subpixel positioning of objects to get more
| accuracy than full pixel steps.
| yshklarov wrote:
| To nitpick with the grammar in the quote: It's capable of
| measuring to the accuracy of 120 mm at 1000 km. So it cannot
| accurately measure the diameter of a human hair (which ranges
| from around 20 to 200 mm) at that distance, but only _to the
| accuracy_ of a human hair.
| perihelions wrote:
| You're right: this precision is hundreds of times below the
| diffraction limit of even the James Webb telescope. It
| can't possibly measure the _width_ of an object that
| finely; rather, only the relative displacement of its
| centroid position between two points in time. (And it 's a
| seriously confusing physics miracle that that much is
| possible).
| jdhwosnhw wrote:
| For point source astrometry, there are a few ways to beat
| the diffraction limit. For instance, some observers will
| purposely defocus their optics to spread the target
| photons over a larger number of pixels, which with
| sufficient SNR lets you gain a better lower bound (from a
| Cramer Rao perspective) on precision. I think Gaia
| actually does something similar to this but "blurs"
| through time, rather than across space, by purposely not
| perfectly tracking stars so that they drift at sub-pixel
| rates across the FPA.
| Qem wrote:
| Hope they have captured an image of Planet Nine somewhere there,
| and eventually are able to pinpoint it.
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