Construction of ESA Galaxy Mapping Satellite Completed

coondoggie writes with an article in Network World. From the article: "The European Space Agency says it has completed what it calls the largest digital camera ever built for a space mission — a one billion pixel array camera that will help create a three-dimensional picture of the Milky Way Galaxy. Set to be launched onboard the ESA's galaxy-mapping Gaia mission in 2013, the digital camera was 'mosaicked together from 106 separate electronic detectors.' ESA says that Gaia's measurements will be so accurate that, if it were on Earth, it could measure the thumbnails of a person on the Moon."

Comments

Leo

[pablo_max]

No, only if we could leave low Earth orbit and actually use said map.

Re:Leo

[djlemma]

If we were going somewhere that this satellite was trying to map, then I think leaving LEO would be one of the lesser challenges...

Re:Thumbnails?

[blair1q]

The moon is about 4e8 m away. A thumbnail is about 1e-2 m across. This telescope can resolve things 1e-10 in size relative to distance.

The center of the galaxy is 1e16 m away. 1e16 * 1e-10 = 1e6.

This telescope can directly image objects 1000 km across at the center of the galaxy.

May I just say, holy fuck!

Camera finished, not satellite

[Trapezium Artist]

To avoid any confusion, we have finished the assembly of the focal plane assembly (i.e. those 106 large CCDs), but not the full-up satellite itself. That still has a way to go, with launch likely at the end of 2012 or early 2013. But it's nevertheless a great achievement to have the huge detector array done and is a real milestone for us.

Also, Gaia isn't taking pretty pictures of the sky per se: via repeated scans over the sky, it's going to provide extremely accurate positions and velocities for about one billion stars in the Milky Way, allowing us to trace their motions back (and forward) in time, and thus understand how the Milky Way was put together in the first place. It does much, much more than that, so if you're interested, I suggest you follow the link in the original submission for more.

(DIsclosure: I work for ESA and am close to the project)

Re:Camera finished, not satellite

[Trapezium Artist]

Not really; these are very specialised custom CCDs made for Gaia alone, to its specific requirements. Because of this, they're a very long lead item and need to be tested rigorously, which means that they needed to be done early. That said, most of the parts of Gaia are ready by now, and the remaining time before launch will be needed for integration and testing of the whole system.

While you're right about the rapid pace of detector development in the commercial sector, those are very different beasts to the ones needed for most scientific applications. For one thing, we almost exclusively use "black-and-white" detectors, i.e. which can image a single colour or single band at a time through a filter: we need this to ensure the highest sensitivity to faint sources. We can then make colour pictures later by superimposing images taken in several different bands. We also generally use very long exposures, so we need detectors which work at very low temperatures to avoid dark current noise. Finally, we can usually tolerate slightly imperfect detectors in terms of dead pixels, because we usually take a series of dithered images and can fill in the bad pixels later. On the other hand, we really care about low read noise.

Commercial detectors these days usually take colour pictures straight off, by having clusters of RGB pixels on chip. Cosmetic quality is at a premium, but dark current noise is less of an issue. Finally, they usually run warm, not at cryogenic temperatures. Many commercial imaging sensors are in fact CMOS devices now, whereas CCDs still pretty much rule the roost for optical imaging in astronomy. That said, I was approached at this week's UK Space Conference in Warwick by representatives from e2v, the suppliers of Gaia's CCDs, wanting to talk to me about scientific uses of their CMOS line :-)

Imagine if it had really BIG mirrors!

[wisebabo]

By the scale of the upcoming James Web Space Telescope or even by the Hubble Space Telescope, GAIA has some pretty small primary mirrors (1.45m). Hell, there are probably some amateurs with telescopes with bigger mirrors than that (though not 1.5 million kilometers in space!). I'm amazed that with such small mirrors it will have the sensitivity to do all that is claimed it will like find (hopefully) tens of thousands of brown dwarfs which are very dim (hence the name). (Of course ACCURACY not sensitivity is the main goal of this thing, that's why even though it could have the resolution to pinpoint a thumbnail on the moon it couldn't see it unless it was a very bright thumb!)

Still I am not a professional astronomer and since this is being done by the same(?) people as who created hipparcus, the previous spacecraft of this type, I'm optimistic that it will be equally successful. Someday we can hope here will be a version of this with really big mirrors, maybe that will allow us to get the remaining 99% of the galaxy. Still to think that soon we may have a pretty good 3D model of the galaxy (with a billion 3D data points) is amazing considering that the only comparable example of this was in Star Trek Voyager's "Map Room" set several centuries in the future! And they were still lost!

If one of the goals of astronomy is to show humanity's place in the universe, I think this goes a long way to fulfilling it. I really really want the 3D dataset when it comes out after 2018 so I can take my own virtual voyages through the milky way!

Re:Thumbnails?

[jpapon]

This telescope can directly image objects 1000 km across at the center of the galaxy.

Well, maybe, but that's assuming said object is really luminous. Sure, you can get 1000km resolution on a star, but it does you no good to have 1000km resolution on an exoplanet if the number of photons reaching you from the exoplanet are less than your noise floor. I could be wrong, but I don't think this resolution is *quite* as exciting as it sounds... unless of course you attach it to some wide aperture high quality optics.

Re:Thumbnails?

[djdanlib]

Hooray for being someone who gets that.

Everyone goes ga-ga over the number of megapixels, while the professionals care about subject material and the sensor's dynamic range, gain characteristics and noise floor.

Different century, same old stupidity:

[Hartree]

Was your great grandpappy one of those who was laughing at the Wright brothers and saying "If man were meant to fly, he'd have wings."?

Or are you just a researcher whose proposal didn't get funded?

Re:NASA must be pissed

[JWSmythe]

    Yup. There was someone ranting one day about how much NASA spends, so I took the time to go through the federal budget numbers, break it down, put it back together, and showed how insignificant the NASA budget was compared to other things that we really don't need and shouldn't be doing.

    Consider how much money has been put into new fighter aircraft, when there isn't an enemy with the capability of deploying aircraft to even get to CONUS. Some of the projects are dropped after spending billions, and not a single aircraft has made it to production. I could go on for hours about the DoD spending, and how it's not helpful in the least to the people of the United States. The government claims these wars we're fighting now are to help Americans, but there hasn't been a legitimate threat of war by any country against CONUS since WWII.

    Even during the cold war, the threats were inflated by both sides, and the military buildup existed as more of a show of force to their own citizens, than to scare the enemy. Instead of this huge wartime budget that we've been burying ourselves with, this could easily be peace time. That's only the financial side of it. The discussion of the lives of our soldiers, both in deaths and life changing effects could be nil, *AND* we could have had sizable research stations on the moon, Mars, and other objects in this solar system. Instead, we're looking at the last launch of the only American spacecraft capable of carrying humans on Friday morning. Our only fallback plan is the rough equivalent of selling your car, and hitching rides with your neighbors to get anywhere. That's particularly odd that we're now to depend on our cold war enemies to furnish our only way to space. We've forgiven them, but still have harsh sanctions against Cuba for housing a few Russian missiles decades ago, and sending them back to Russia years before most people reading this were ever born. That's November 1962, for those who may be wondering.

    How much is wasted continuing the nonsense against an enemy who hasn't done anything against us in almost 50 years?