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Gaia making a 3D-map of a Billion stars, new space observatory
Holder of the Tw...
post Dec 16 2013, 07:39 PM
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Gaia and its Soyuz rocket are on the launch pad, with the attempt to launch it set for this Thursday. It will be in the very early morning hours for most of us in North America. For those who want to get up (or stay up?) to watch, Spaceflight Now will carry live streaming video. Their mission status center for Gaia is at this LINK.. This will be the link for the liftoff as well.

Several websites for Gaia have recently been added or changed. Here is the recent list:

ESA basic overview
ESA factsheet
ESA in depth
Scientific community advanced website (new web address)

Also:
Launch kit (in English)
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Explorer1
post Dec 19 2013, 07:51 AM
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Launch in 90 minutes...

http://spaceflightnow.com/soyuz/vs06/status.html
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Hungry4info
post Dec 19 2013, 10:07 AM
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Looks like launch was successful smile.gif


--------------------
-- Hungry4info (Sirius_Alpha)
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helvick
post Dec 19 2013, 10:50 AM
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Lots of rather odd (to me) claims being made about the resolution of Gaia's imaging system - Human hair at a thousand miles, penny on the moon etc. I've started to dig into the science instrument documents and the expected resolution of the astrometry is in the single digit micro-arcsecond range but I'm a bit at a loss as to how a ~1.45x0.9m telescope can get those results given diffraction limits.

So I assume there's some other techniques being brought to bear that allow it to get to a "resolution" 1000x Hubble at it's best and I'm assuming that the resolution only applies in the specific case of the task in hand.

Just asking in case anyone has any pointers to the maths\theory behind what they are doing. Will be looking myself and post as soon as I find something.
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Gerald
post Dec 19 2013, 01:36 PM
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Without reading the documents, just as a hint how to look at the claims:
They won't be talking of resolution in the usual optical sense, meaning distinguishing two objects, but of the determination of the position of a star.
If you take a Gauss bell curve, you can determine the maximum/average with a much higher precision than separating two superposed bell curves, where you need about one sigma.
The other trick is using two telescopes to increase the effective aperture along one line; they originally intended to use interferometry, but seem to have found an even better solution.

Edit: You'll find much more detail in the DPAC Newsletters.

To add some more basis (Newsletter 17):
QUOTE
Since Friedrich Bessel announced in 1844 that Sirius and Procyon had an unseen companion, it is well known that they can be detected through the wobble in the star proper motion. In fact, when the luminosities of the components are not very different, we do not observe the motion of the brightest star around the barycentre, but the motion of the photocentre, which is the luminosity centroid.

AGIS on the Powerpoint level.
Some math.
AGIS in a nutshell.
Details behind the paywall.
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Ron Hobbs
post Dec 19 2013, 03:11 PM
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OMG.

Video of the launch of Gaia is awesome. It is informative, historical and just downright beautiful. It is the 1,813 launch of the an R-7 derived vehicle, the 6th from the Western Hemisphere. You can see the separation of the boosters, what the Russians call "Gagarin's Cross." As Gaia flies into the dawn, you can see the boosters fall away, looking like "twinkling stars."

Watch it full-screen and enjoy.

http://spaceinvideos.esa.int/Videos/2013/1...unch_-_Lift-off
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pospa
post Dec 19 2013, 05:01 PM
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QUOTE (Ron Hobbs @ Dec 19 2013, 04:11 PM) *
You can see the separation of the boosters, what the Russians call "Gagarin's Cross."

Wrong. They call it "Korolev cross".
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Greenish
post Dec 19 2013, 06:06 PM
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QUOTE (helvick @ Dec 19 2013, 05:50 AM) *
So I assume there's some other techniques being brought to bear that allow it to get to a "resolution" 1000x Hubble at it's best and I'm assuming that the resolution only applies in the specific case of the task in hand.

Gaia measures parallax. So the 'aperture' is up to the diameter of the Earth's orbit (EDIT: this is what allows accurate distance measurements. But as Gerald pointed out above, it is the use of two telescopes fixed at a well-known angle, repeatedly viewing a large swath of space -- plus some fancy math -- that allows angular precision well beyond telescopic diffraction limits).

Regarding the specifics of how they combine multiple measurements, in addition to the above links, this document is a good one: http://www.ast.cam.ac.uk/ioa/iau_comm8/iau...s/deBruijne.pdf (start with pg 2, "Gaia astrometry in one viewgraph")
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Ron Hobbs
post Dec 20 2013, 03:33 AM
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QUOTE (pospa @ Dec 19 2013, 09:01 AM) *
Wrong. They call it "Korolev cross".


You are so right. I knew I should have looked that up before I posted. Now we can see it over the Atlantic.
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Gerald
post Dec 20 2013, 08:52 AM
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ESA Gaia on Twitter
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Holder of the Tw...
post Jan 8 2014, 02:58 AM
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According to the latest Tweets, Gaia has successfully completed its L2 injection burn and arrived at its destination.

In addition, the camera has been turned on and has sent its first images. Currently undergoing quite a bit of testing, but so far it looks good too.

Article on the camera testing at this LINK.

Update: Gaia enters its operational orbit.

Well, now it's going to be a few years ...
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Doug M.
post Feb 7 2014, 09:56 PM
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GAIA is going through shakedown -- testing and calibration. (That's supposed to last until May, I gather.) So they just posted a first test image: http://www.esa.int/Our_Activities/Space_Sc...omes_into_focus. Apparently there won't be a lot of these, since making images isn't what GAIA is about.


Doug M.
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Tom Womack
post Feb 8 2014, 12:19 AM
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http://hla.stsci.edu/cgi-bin/display?image...olor)%20NGC1818

is the equivalent image from Hubble; I'm guessing they're using NGC1818 as a calibration target because it has the very distinct red and blue star series that you can see in the Hubble shot
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SteveM
post Jun 17 2014, 02:45 AM
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Good overview of current understanding of Gaia's stray light problem and its effects on observations.
http://blogs.esa.int/gaia/2014/06/16/preli...and-strategies/
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SteveM
post Jul 29 2014, 01:33 PM
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Gaia enters routine phase:

"Last week Friday, 25 July 2014, Gaia started its routine phase by scanning the sky for 28 days using the so-called ecliptic-poles scanning law. This is useful to bootstrap the basic calibrations of the data. After these 28 days, the nominal scanning law will be used to determine how Gaia is scanning the sky. Although the commissioning phase has ended, some activities remain to be completed. The root causes of the stray light and the basic-angle variations have not been found yet."

More at http://www.cosmos.esa.int/web/gaia/news_20140729
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