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Fermilab Builds 500-Megapixel Camera
heyitsme writes "Fermilab, a U.S. Department of Energy research lab, is part of a collaboration on an experiment to measure the properties of dark energy. The Dark Energy Survey would measure the history of the expansion rate of the universe more precisely than ever before, using the largest camera ever built with Charge Coupled Devices (CCD). The 500 megapixel Dark Energy Camera (DECam) would be placed on an existing 4-meter telescope located in north-central Chile at the National Optical Astronomy Observatory's Cerro Tololo Inter-American Observatory. The DECam together with the CTIO 4-meter telescope will allow for a survey of 15 percent of the sky to light levels faint enough to measure the colors of galaxies at redshift one."
The detector actually contains roughly 503,316,480 raw pixels, this amounts to slightly less than 500,000,000 effective pixels after initial processing.
The data will, of course, be stored directly to a large SAN storage system, probably from EMC or Hitachi.
The detector should generate single frame images of roughly 1.7G prior to post-processing, and roughly 700M single-frame image files after processing to TIFF or PNG format.
(Not an expert, they're all fast asleep right now.)
One of the things Fermilab is trying to do is get a measurement of the so called weak lensing effect. Matter distorts spacetime, and light is thus bent as it passes nearby a big cluster. This is gravitational lensing.
Famously, it is seen as "strong" lensing -- when the source is very close on the sky to the cluster, and the light gets bent enough that there are multiple images. Nobody really believed it could happen, but then in the last decade or so it's become an accepted and popular thing to play with and observe.
Weak lensing is when there are no multiple images, and instead only a slight distortion. Much harder to see and measure -- you basically look for a whole bunch of galaxies that are slightly distorted.
That means you need a very wide field of view -- to get enough galaxies quickly enough -- but also a very good resolution -- to be able to measure the slight distortions. Hence the need for such an insane[ly cool] device.
Why go through all this trouble? Well, weak lensing is one of the view ways to measure all the matter in the universe on very large scales. Because nearly all the matter is supposed to be invisible, in the past people have used various "tracers" that we can see. But there's a huge amount of debate as to how good the various tracers are, and, of course, you need a direct measurement to be sure you're not off in la-la land.
Weak lensing measures it all because all matter, regardless of how bright it is, bends spacetime in the same fashion. So, if you can get a good weak lensing measurement, you can theoretically create an unbiased map of the matter distribution. No need to cross your fingers and hope that some tracer is behaving properly.
It all fits into dark energy because dark energy is supposed to alter the extent to which matter can cluster (roughly speaking, dark energy behaves like antigravity, and pushes things apart, stopping them from falling together.)
Of course, weak lensing is just one of the things this guy is meant to do -- there are lots of other neat things that hopefully someone more awake than I can describe.
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Although the article does say 500 megapixel, a simple calculation could answer your question. The CCD is composed of elements giving it a pixel array of 180k X 240k pixels giving us 28800000000 pixels! (Assuming each pixel holds one grey value in a 16 bit image ) Working from 16 bits/pixel and 8 bits/byte, we are looking at 2 bytes per pixel. So 2 bytes * 28800000000 pixels gives us 57600000000 bytes or almost 54 GB/image!
If you were to take multispectral or even RGB images, one would multiply the file size by the appropriate dimension.....
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Anyway, with 500MP you're going to be severely limited by the resolving power of the lens. It's quite difficult to get even 100 line pairs per mm with the best 35mm photographic lenses (lenses for larger formats tend to be much worse because it's harder to maintain accuracy over a large glass area, plus it's not as necessary with lower enlargement factors). A 500MP sensor needs a pretty exceptional telescope in front of it.
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So 960 million bytes per frame, which is only 915.5MB (1M = 2^20).
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Ummmm......I think it is too late and past my bed time. A quick rechecking of the numbers reveals a total of 960000000 bytes for each image in a 4800000000 pixel array giving us a much more manageable total of approx .9GB/image in raw form (again, assuming a 16 bit image).
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... if the camera is 500MP then yes the digital zoom would in fact be useful, being that the resolution is so massive you can keep zooming in and zooming in for a very long time before there's any noticable degradation in image quality (assuming a perfect lense etc here which is not possible). what i'm pretty sure he meant was, say take a photo from 200m above a busy city st, and u could sit there for hours and hours just zooming in on that photo looking at cracks in the sidewalk or the hairs on peoples heads.
CMOS is cheaper and can transfer the image faster off of the chip, but CCDs offer lower dark noise and lower reading noise, which means that your pictures are clearer and more scientifically usuable. CCDs are also INCREDIBLY more sensitive than CMOS, with the newer chips able to get upwards of 85% efficiency.
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You could fit a few pictures on this 12GB CF:e tec12 gb.asp
http://www.dpreview.com/news/0405/04052601pr
Only $14,900
Not in the article, but in their submission of proposal to Fermilab PAC, they state
So, not more data per image, just more images.Though parent is (+5, Funny), the answer to his question is most likely yes. In all the time I've spent in various physics research labs, I've never seen anything *but* Linux. The story would be different if the CCD was being launched (in which case it would probably run on a specially written variant of VAX). But the drivers/utilities for land-based devices are written almost exclusively by the scientists themselves (not engineers), and most of them stick with Linux.
Not really. If you're looking for a decent A4 print, you need at least 5MP. A raw image from this beast contains 100 of those images, so you could use "digital zoom" (actually, just cropping) to concentrate on specific parts of the image at perfectly acceptable resolution.
You're right about the general uselessness of digital zoom on low-end digicams, but this is a different beast.
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In fact, the Sloan Digital Sky Survey (in which Fermilab also plays a major role) transfers its imaging data from the the observatory to Fermilab (where it is reduced) by FedExing DLT tapes. I do not know what it planned for the DEC.
There seems to be a lot of interest all of a sudden on slashdot on super high res images (yesterday there was an article on a large film camera which was by no means revolutionary or record setting). It's really not that cutting edge. If you go to www.betterlight.com, they're releasing a 4x5 back capable of 10200x13800 pixels soon, and already have one available that's about 100 Mpixel. Granted, these are slow, but they've been available for a long time and are used daily by product photographers. I shoot 4x5 myself on film and make 550 MB scans. It's relatively cheap and very high res.
TIFF or PNG? Who in the world uses anything other than FITS for astronomical images?
>youu can keep zooming in and zooming in for a very long time before there's any noticable degradation
I think a better way to put it would be that here is that if you want a smaller image( less information) you can selectively crop it out. If you're targeting 1-2 megapixels final size, you could be quite selective in finding the perfect picture in a 500 megapixel image.
Digital "zoom" is badly named because it's not really a zoom, it's a crop, followed by a resample. In practice most people find that they want to take full resolution pictures all the time, and save the cropping for later, on their PC - where they can have tighter control. I imagine that the buyers of this device would have a huge storage device to attach to it, and still do the same thing.