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"Synthetic Tracking" Makes It Possible to Find Millions of Near Earth Asteroids

Unknown Lamer posted about 7 months ago | from the found-one dept.

Space 101

KentuckyFC writes "Astronomers think that near-Earth Asteroids the size of apartment blocks number in the millions. And yet they spot new ones at the rate of only about 30 a year because these objects are so faint and fast moving. Now astronomers at the Jet Propulsion Laboratory have developed a technique called synthetic tracking for dramatically speeding up asteroid discovery. Insteads of long exposures in which near-Earth asteroids show up as faint streaks, the new technique involves taking lots of short exposures and adding them together in a special automated way. The trick is to shift each image so that the pixels that record the asteroid are superimposed on top of each other. The result is an image in which the asteroid is sharp point of light against a background of star streaks. They say synthetic tracking has the capability to spot 80 new near Earth asteroids each night using a standard 5 metre telescope. That'll be handy for spotting rocks heading our way before they get too close and for identifying targets for NASA's future asteroid missions."

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101 comments

What's the size of an apartment block? (1)

Anonymous Coward | about 7 months ago | (#44895149)

How many hedgehogs to an apartment block?

Re:What's the size of an apartment block? (1)

Russ1642 (1087959) | about 7 months ago | (#44895929)

Roughly ten thousand olympic swimming pools.

Re:What's the size of an apartment block? (1)

G3ckoG33k (647276) | about 7 months ago | (#44896473)

Yet noticeably smaller than Wales.

Re:What's the size of an apartment block? (1)

cusco (717999) | about 7 months ago | (#44897203)

Blue Wales, or Pilot Wales?

Re:What's the size of an apartment block? (0)

Anonymous Coward | about 7 months ago | (#44899541)

Jimmy

Re: What's the size of an apartment block? (0)

Anonymous Coward | about 7 months ago | (#44899625)

Timmy, Timmy, Timmy.

Re:What's the size of an apartment block? (0)

Anonymous Coward | about 7 months ago | (#44899885)

You forgot sonic wails.

Is it just me? (4, Interesting)

Score Whore (32328) | about 7 months ago | (#44895157)

Or does the submitter not see the apparent logical flaw in the way the described this process. If you're going to line up each image so that the asteroid is a single sharp pixel and the stars are streaks, doesn't that suggest that you already know which pixel is the asteroid? In which case you don't really need to search for that particular asteroid, no?

At a minimum the submitter or the editors need to think whether their description of the procedure is good.

Re:Is it just me? (1)

TheCarp (96830) | about 7 months ago | (#44895229)

Yes and no. I was thinking the same thing but, what if you do the process multiple times, shifting in different directions each time, and possibly again with different amounts of shift per frame? Then you have maybe 8 or even 80 different results to look at, which could be weeded out by algorythmically rejecting any that contain no bright spots.

Re:Is it just me? (1)

TheCarp (96830) | about 7 months ago | (#44895351)

An apartment block would be about .04 furlongs across. You should be able to figure it out from there.

Re:Is it just me? (1)

Gilmoure (18428) | about 7 months ago | (#44895427)

Ah, but I was wondering about volume in hogsheads [traditionaloven.com] .

Re:Is it just me? (1)

bdwebb (985489) | about 7 months ago | (#44898597)

Babies is the correct unit of measure, actually. Babies provides a unique unit of measure in that it is minimally variable but, when averaged and used as a constant, can provide a standard unit of measure for determining length, width, speed, time, weight, etc...the possibilities are endless! Almost anything that can be measured can be measured in babies. Imagine - no more confusion between metric or standard...Babies is the answer!

All units below are based off an average newborn baby:
B = Baby (Avg. Length) = 20in. = 50.8cm
Bt = Baby Time = 273.75 days (9 months x 30.4166 days) = 23,652,000 seconds
Bw = Baby Weight = 7.75lbs = 3.515kg
(While there are individual units of measure listed above, all should be referred to simply as 'babies' for scientific documentation purposes as the applicable unit of babies is implied by the circumstance.)

Taking the .04 furlongs across example and converting to babies (assuming this is a square apartment building with a standard 10ft ceiling, .04 furlongs by .04 furlongs by 10ft.), we get a volume of about 1,505.43 babies cubed. Imagining then that this is an asteroid traveling at the fastest speed currently listed on JPL's Current Impact Risks page [nasa.gov] , 19.14km/s, we can also extrapolate that it would be traveling at a rate of 37,677.15 babies/second. Therefore, this would be an object with a volume of roughly 1,505.43 B traveling at a rate of 891,139,951,800 B/Bt.

IMPORTANT NOTE: Do NOT measure in DEAD BABIES. Dead babies is a wildly variable measurement and heavily dependent upon the circumstance of baby death, lifespan, birth defects, and missing parts.

Re: Is it just me? (0)

Anonymous Coward | about 7 months ago | (#44899637)

Haha, so funny. I rate it as 4 of 5 babies. Also, some mod this up a baby.

Re:Is it just me? (1)

brainboyz (114458) | about 7 months ago | (#44895381)

That's exactly what they're doing: brute force analysis. All directions and all "reasonable" variations of speed for a given series of spot pictures, then filter for spot intensity. Decent use for super computing.

Re:Is it just me? (0)

stenvar (2789879) | about 7 months ago | (#44895715)

No, rather a complete waste of supercomputing, since there are already better algorithms for doing the same thing.

Re:Is it just me? (1)

Anonymous Coward | about 7 months ago | (#44896043)

No, rather a complete waste of supercomputing, since there are already better algorithms for doing the same thing.

Yeah, because the scientists at JPL are all idiots compared to some random douchebag on Slashdot who thinks he knows everything.

Re:Is it just me? (1)

Garridan (597129) | about 7 months ago | (#44898057)

Sad but true. Most anonymous cowards are experts in every field of art, math, and science. If only they spent their time using their knowledge, and not just faffing about on slashdot and complaining about the idiot "experts" that have spent their entire adult lives learning about one tiny little topic... and fail utterly to understand the brilliance of this untapped resource. So sad. I'm going to go drown myself in my research.

Re:Is it just me? (0)

Anonymous Coward | about 7 months ago | (#44898471)

Go ahead and do that. Then produce some better papers than this. I sure do.

Re:Is it just me? (0)

Anonymous Coward | about 7 months ago | (#44899905)

You remind me of that guy from the first season of Scrubs, Dr Jeffrey Steadman:

http://www.youtube.com/watch?v=ALSgHK703DU

Yeah. That's you alright. Keep up the good work! We'll know who to ignore from now on.

Re:Is it just me? (0)

Anonymous Coward | about 7 months ago | (#44904673)

No, rather a complete waste of supercomputing, since there are already better algorithms for doing the same thing.

Actually, if you take 5 minutes to scan the actual paper, you'd see that they are using a single GPU and clever algorithms and analyse data virtually in real time (10 seconds to analyse 30 seconds of data). Page 4, the last paragraph, if you care to read.

Re:Is it just me? (5, Insightful)

edmudama (155475) | about 7 months ago | (#44895287)

Article doesn't have a good description.

My guess is you take a bunch of timelapse frames of the same sky.

Then you overlay them at offsets in different directions which would keep any moving objects in the same place.

Picture doing 36000 sequences of overlays:
360 degree variation in 0.1 degree increments at 10 different radial velocities

Most of those sequences will just show blurred gray washout, but if you happened to hit the right direction as a moving object at the right speed, your overlaid image sequence will effectively keep the moving object in the same spot of the frame, which will result in the average brightness for that pixel or pixles to be higher than the surrounding blurs.

Just a guess...

Re:Is it just me? (1)

moteyalpha (1228680) | about 7 months ago | (#44895383)

That was actually brilliant. That was several orders of magnitude more interesting than the summary.
But you lose a point for not converting distance to international standard apartment block scale.

Re:Is it just me? (1)

Geirzinho (1068316) | about 7 months ago | (#44895645)

Interesting idea, I wonder if that's ever been tried? I guess the feasibility depends on what the angular motions of these objects are.

In this case though, they "simply" take a lot of short-exposure images of the same region and add them together. From the abstract:

The technique relies on a combined use of a novel data processing approach and a new generation of high-speed cameras which allow taking short exposures of moving objects at high frame rates, effectively ``freezing'' their motion. Although the signal to noise ratio (SNR) of a single short exposure is insufficient to detect the dim object in one frame, by shifting successive frames relative to each other and then co-adding the shifted frames in post-processing, we synthetically create a long-exposure image as if the telescope were tracking the object with a significantly higher SNR.

Re:Is it just me? (1)

wagnerrp (1305589) | about 7 months ago | (#44898785)

Interesting idea, I wonder if that's ever been tried?

See Inverse Synthetic Aperture Radar [wikipedia.org] . It's basically just taking it one step further. Where ISAR starts with the assumption that you know where something is, and thus know how to shift the captures to produce the synthetic image, this brute forces the computation and waits for a sufficiently strong signal to show up.

Comparison? (1)

gr8_phk (621180) | about 7 months ago | (#44895909)

How does this compare to using regular edge detection to find faint streaks in a time lapse image? How about after detecting bright spots and deleting them followed by edge detection?

Re:Is it just me? (2, Informative)

Anonymous Coward | about 7 months ago | (#44896391)

Article doesn't have a good description.

Before the detection of the NEA, its velocity vector is unknown. However, we find this vector by conducting a search in velocity space. To do this we have developed an algorithm that simultaneously processes the synthetic tracking data at different velocities. The velocities searched initially have (x,y) components that are multiples of 1 pix/frame in each direction. This is a computationally intensive task: for example, the shift and add process for 120 images for 1,000 different velocity vectors requires over 1011 arithmetic operations. However, with current off-the-shelf graphics processing units (GPU) with up to 2,500 processors and teraFLOPS peak speeds, we were able to analyze 30 sec of data in less than 10 sec. Once the NEA is detected in this initial search, an estimate of velocity becomes possible. Using this velocity we refine the astrometry relative to a reference star in the field and determine the velocity to a much higher precision. Elsewhere we plan to describe the details of the synthetic tracking algorithm and report its performance, including its false alarm rate.

Re:Is it just me? (0)

Anonymous Coward | about 7 months ago | (#44901837)

Why don't you blur the image prior to this? That way a small faint spot becomes an even fainter large circle, but when you start adding snapshots, you will have greater overlap of those faint circles without need for finding exact speed. It is something similar to Heisenberg principle: you can get better detection of speed by forgoing exact detection of position, on first pass, but then when you have detected that something is moving out there, you can reiterate with less blur, until you single it out.

Or else, do alternative adding and subtracting of successive frames, to suppress anything that stays in place

Re:Is it just me? (1)

Anonymous Coward | about 7 months ago | (#44897645)

For anyone who wants to look into this, the above is a description of a standard computer vision algorithm called the generalised Hough transform. Its one of those really old techniques that has stood the test of time and remains useful for real problems today.

Re:Is it just me? (3, Interesting)

kruach aum (1934852) | about 7 months ago | (#44895289)

"If it were moving at speed v, it would show up when I shifted the pictures by x pixels." Repeat for likely ranges of v, watch for bright spots. No contradictions required.

Re:Is it just me? (0)

Anonymous Coward | about 7 months ago | (#44900019)

Also, if you know what orbital velocities to expect, the range you have try can be reduced.

Re:Is it just me? (4, Informative)

Baloroth (2370816) | about 7 months ago | (#44895361)

From TFA:

The difficult part of this is knowing which way to shift each image. Shao and co have solved this by brute force: they take consecutive images and examine all possible shifts to see which resolves the fast moving asteroid.

That's a lot of computation (they try 1,000 different velocity vectors), but that's what computers are really, really good at.

Re:Is it just me? (3, Interesting)

mdielmann (514750) | about 7 months ago | (#44896989)

Sometimes the best way to solve a big problem is to just get a bigger hammer.

I had a problem once that I could probably have solved using some very pretty, complex, elegant formula. But after examining the problem space, I figured I could brute-force it, with a basic fitness algorithm, in about 2 seconds. The overall process it was a part of took between 90 and 300 seconds. The other benefits were, it was quite readable, and didn't require any advanced math or knowledge of the problem to see what was being done. The fact that the pretty formula would have improved performance at most about 2% made it an easy choice.

Re:Is it just me? (1)

VortexCortex (1117377) | about 7 months ago | (#44901403)

Congratulations. You have discovered how thinking beings solve problems. Consider this planet a computer brute forcing the answer not to emergence of sentience, but also to the most ironic way to become extinct.

Re:Is it just me? (1)

Anonymous Coward | about 7 months ago | (#44895373)

As the material in the second link states, computationally they do a brute-force approach, trying all possible directions and speeds of drift of the object, then look at any resultant images that show a single object. A nightmare from a computational complexity approach, but with the amount of HPC horsepower out there these days, a workable one.

Re:Is it just me? (1)

fast turtle (1118037) | about 7 months ago | (#44896579)

they probably just use a quad SLI setup with Nvidia GPU's to do this. Something they'd be perfectly adequate for

Re:Is it just me? (1)

wagnerrp (1305589) | about 7 months ago | (#44898805)

No, they probably don't. You only use SLI because you need to share and merge graphical output onto a screen. When you're doing computational work, you just have a server with a bunch of compute cards.

Re:Is it just me? (1)

Neil Boekend (1854906) | about 7 months ago | (#44899789)

Nope, separate GPU's work fine for this. And not 4. And without the useless graphical outputs.
href=https://www.trustedsec.com/february-2011/building-the-ultimate-bad-arse-cuda-cracking-server/>Something akin to this.
although there certainly are updated versions available, for large operations. This was from 2010, but I couldn't find a more recent picture.

Re:Is it just me? (0)

Anonymous Coward | about 7 months ago | (#44895485)

From the TFA:

The difficult part of this is knowing which way to shift each image. Shao and co have solved this by brute force: they take consecutive images and examine all possible shifts to see which resolves the fast moving asteroid.

Given that a sequence of images may contain 120 pictures, that’s a computationally intensive task. “The shift and add process for 120 images for 1,000 dierent velocity vectors requires over 10^11 arithmetic operations,” they say.

But that’s chicken feed for state-of-the-art computers. “With current o-the-shelf graphics processing units with up to 2,500 processors and teraFLOPS peak speeds, we were able to analyze 30 sec of data in less than 10 sec,” they say.

Re:Is it just me? (0)

Anonymous Coward | about 7 months ago | (#44895551)

Imagine if you just RTFA'ed ...

Re:Is it just me? (1)

K. S. Kyosuke (729550) | about 7 months ago | (#44895641)

The thing you have to guess correctly (and try in large numbers) is the apparent motion vector, not the position.

Re:Is it just me? (2)

dogsbreath (730413) | about 7 months ago | (#44896971)

Yes the description may be flawed but seems to me that this is essentially a technique that has been in use for a long time, at least back to the 1950's, with systems like surveillance radar where several ping round trips are superimposed (added together). Involves delaying/storing the received signal and adding back together in a time correlated manner. Noise tends to reduce and object reflections tend to reinforce resulting in an effective improvement in the signal to noise ratio. In the early days, analog delay lines were used which also introduced noise but which would also cancel out.

With high performance computing it is not hard to imagine compensating for and correlating frame position, observer location, time etc.

Even if the object has a velocity such that there is no reflection signal increase, background noise will be decreased.

Re:Is it just me? (1)

wagnerrp (1305589) | about 7 months ago | (#44898837)

It's basically an enhancement on the traditional [inverse] synthetic aperture methods. With SAR, you know where everything is, roughly, and you're using the technique to refine the image. In this, you use the technique blindly, and wait until something rises up out of the background noise.

STANDARD UNITS, PLEASE (2, Funny)

Anonymous Coward | about 7 months ago | (#44895159)

Wha...? Asteroids the size of apartment blocks?

Can we please have this measurement in a standardized unit, like Volkswagen beetles?

Man. I thought Slashdot was going downhill back when it was mostly a CueCat fansite, but this really takes the cake.

Re:STANDARD UNITS, PLEASE (3, Insightful)

oodaloop (1229816) | about 7 months ago | (#44895261)

Really? This is what takes the cake? The dupes, slashvertisements, missing or dead links, dupes, obvious grammar and spelling mistakes, dupes, pointless articles like how to re-open tabs, and lest we all forget, the dupes. But citing an article that uses apartment blocks as a reference is what does it for you?

Re:STANDARD UNITS, PLEASE (0)

Anonymous Coward | about 7 months ago | (#44895829)

I see what you what you did there. Slashvertisements sounds like a very different thing than what it mean on ./. It makes me wonder, are these Brit apartment buildings or American apartment blocks. I'm leaning towards the building sized rocks.

Re:STANDARD UNITS, PLEASE (1)

drainbramage (588291) | about 7 months ago | (#44895433)

Which is worse, using 'apartment blocks' or 'metre' for measuring.
Is a '5 metre telescope' really a standard?

I have a couple of Meade telescopes but not a 'Metre".

Re:STANDARD UNITS, PLEASE (0)

Anonymous Coward | about 7 months ago | (#44895583)

It is if you speak British English. http://en.wikipedia.org/wiki/Metre

Re:STANDARD UNITS, PLEASE (3, Insightful)

Virtucon (127420) | about 7 months ago | (#44895533)

Ahh but are you talking about VW Beetles from the 1950s and 60s or the fat ones from the 70s? Or perhaps you're talking about the "New Beetle?" or now the "New, New Beetle?" I just want to get some specifics here so I can make sure my bunker can withstand a 20 MegaBeetle impact.

really? (0)

frovingslosh (582462) | about 7 months ago | (#44895179)

Seems like that would only work if you knew the speed and direction that the asteroid was moving in. and, of course, if you knew that then that might not be the one that you needed to find.

Re:really? (0)

Anonymous Coward | about 7 months ago | (#44895367)

Producing fuel for cars sold in the U.S. carries a requirement to meet Clean Air Act standards

Re:really? (1)

Anonymous Coward | about 7 months ago | (#44895403)

Yes. From the article:

"Before the detection of the NEA, its velocity vector is unknown. However, we nd this vector by conducting a search
in velocity space. To do this we have developed an algorithm that simultaneously processes the synthetic tracking
data at dierent velocities. The velocities searched initially have (x,y) components that are multiples of 1 pix/frame
in each direction. This is a computationally intensive task: for example, the shift and add process for 120 images for
1,000 dierent velocity vectors requires over 1011 arithmetic operations. However, with current o-the-shelf graphics
processing units (GPU) with up to 2,500 processors and teraFLOPS peak speeds, we were able to analyze 30 sec of
data in less than 10 sec. Once the NEA is detected in this initial search, an estimate of velocity becomes possible.
Using this velocity we rene the astrometry relative to a reference star in the eld and determine the velocity to a
much higher precision. Elsewhere we plan to describe the details of the synthetic tracking algorithm and report its
performance, including its false alarm rate"

Re:really? (1)

RichMan (8097) | about 7 months ago | (#44895405)

You missed the "synthetic" they take lots of static pictures with the same point over time.
Then use a computer to skew the images it in all the directions and speeds and do the search.

Re:really? (1)

TheCarp (96830) | about 7 months ago | (#44896063)

Sounds like this http://en.wikipedia.org/wiki/Synthetic_aperture_radar [wikipedia.org]

SAR is usually implemented by mounting, on a moving platform such as an aircraft or spacecraft, a single beam-forming antenna from which a target scene is repeatedly illuminated with pulses of radio waves at wavelengths anywhere from a meter down to millimeters. The many echo waveforms received successively at the different antenna positions are coherently detected and stored and then post-processed together to resolve elements in an image of the target region.

So, in this case this case the "moving platform" is, in fact, the earth itself and the "Antena" happens to be able to detect signals in the visible light range.

Great! Just one question... (0)

Anonymous Coward | about 7 months ago | (#44895215)

by any chance, are any of them on course to hit the Capitol, or better yet, Wall Street?

Why not use optical flow (1)

wiredlogic (135348) | about 7 months ago | (#44895247)

It seems like it would be much simpler to just use optical flow to find moving objects.

Re:Why not use optical flow (0)

Anonymous Coward | about 7 months ago | (#44895607)

SNR is way too low.

Re:Why not use optical flow (0)

Anonymous Coward | about 7 months ago | (#44895613)

It seems like it would be much simpler to just use optical flow to find moving objects.

Because asteroids are faint, you need a long exposure to get them distinguishable from noise. So you can composite a bunch of short exposures, and get a distinct image of it and identify its motion, or you can just take a long exposure, then wait for another long exposure so you have two frames to do optical flow calculations with. Of course, with either approach, by taking exposures some time apart instead of back-to-back, you can get a longer time baseline, thus giving you more apparent velocity resolution. And you can be photographing other parts of the sky in-between. It's just that by shift-and-sum, the more exposures you add, the shorter each exposure can be.

Optical flow calculations may be considered a simpler approach (I am not sure in what sense you mean "simple": simple to program? simple for the computer?), but it needs more time on the telescope. Telescope time is much scarcer than either computer time or programmer time, so a more complex algorithm that lets you do more with less scope time is better.

Re:Why not use optical flow (1)

wiredlogic (135348) | about 7 months ago | (#44895977)

Stacking images doesn't just magically produce data from nothing. It is entirely possible to threshold all of the bright objects and/or logarithmically scale the samples and look for motion in the low amplitude region close to the noise floor.

Re:Why not use optical flow (0)

Anonymous Coward | about 7 months ago | (#44896095)

In any individual image, these objects are way below the noise floor. You've got to stack hundreds of images to get the SNR high enough to find the objects at all. Optical flow algorithms need a decent SNR in each subset of images, which just doesn't exist here; the entire set of images is needed to extract the image.

Quit spamming for "medium.com" (5, Informative)

Animats (122034) | about 7 months ago | (#44895357)

"Medium.com" is one of those aggregator sites. Don't link to them. Link to the actual paper [arxiv.org] . Thank you.

They had to use the Palomar 200 inch telescope to make this work. There aren't many big telescopes in the world, and they're booked months in advance. They got a few hours of observing for one night, and good results. But they'd need a lot more observing time on big scopes to do their survey.

Re:Quit spamming for "medium.com" (2)

vriemeister (711710) | about 7 months ago | (#44895799)

Using the 200 meter telescope was just a test, its not necessary to make it work. Read the paper or article, they both say that.

Hough-Transformation (0)

Anonymous Coward | about 7 months ago | (#44895365)

Anyone else thought of that while reading the summary?

Re:Hough-Transformation (1)

gr8_phk (621180) | about 7 months ago | (#44895925)

Yes, but I was thinking "edge detection" which is something different. Conceptually I meant Hough Transform.

Re:Hough-Transformation (1)

wagnerrp (1305589) | about 7 months ago | (#44898915)

First you apply this technique to generate a bunch of synthetic time-lapse exposures. The you use things like Hough Transform to see if it came up with anything interesting, indicating something moving across the sky at that angular velocity. Anything interesting can then undergo further synthetic refinement to help bracket it, or be marked as something worth investigation with more traditional methods.

And yet.. (2)

kryliss (72493) | about 7 months ago | (#44895495)

It always amazes me that the people that complain all the time about Slashdot with dupes, bad articles, etc. come back every day just so they can tell everyone how bad it is. It's as though they sit and wait for it just so they can make long winded comments on how bad Slashdot is. It is getting really old.

Isn't there a simpler way? (1)

Anonymous Coward | about 7 months ago | (#44895523)

Why would you brute-force the pixel shifts to get the asteroid in a single spot, when the fixed background stars are already a stable reference for co-aligning the images? It seems the simpler way (even with the short exposures) would be to cross-correlate and co-align to the background stars, then look for the "dotted" path of the moving asteroid. And isn't it already done this way?

Re:Isn't there a simpler way? (1)

wonkey_monkey (2592601) | about 7 months ago | (#44895647)

I can only guess that in a single image, the asteroid is indistinguishable from noise, and even overlaying the images doesn't bring it out clearly enough to be spotted. Perhaps, once you do all the meta-math, it turns out to be easier just to do many overlays at multiple assumed velocities (which can be filtered down to what we expect of these asteroids) and then look for a bright spot.

Stacking images is simple. Spotting lines of dots in amongst the noise could be fairly tricky to do with any kind of confidence, whereas picking out bright spots (and presumbly then passing on the candidates for more thorough testing) may be less computationally expensive.

But what do I know? I ain't no computational astrophysicist.

Re:Isn't there a simpler way? (0)

Anonymous Coward | about 7 months ago | (#44896817)

Why would you brute-force the pixel shifts to get the asteroid in a single spot, when the fixed background stars are already a stable reference for co-aligning the images? It seems the simpler way (even with the short exposures) would be to cross-correlate and co-align to the background stars, then look for the "dotted" path of the moving asteroid. And isn't it already done this way?

They do it this way so you can actually detect the very faint asteroid from the series of single short exposure photos. That is the whole point of the technique over the existing technique which s already used and which you described.

Instead of long exposures looking for streaks where the stars are motionless, you stack the faint single photos of the asteroid over top of each other. If it is moving in the direction and speed that you are "testing" for, it should appear out of the noise as a bright point, otherwise its just noise that cancels out and reveals nothing. Then you test many combinations of speed and direction until you find something significant.

Amateurs (0)

Anonymous Coward | about 7 months ago | (#44895593)

I don't get what's so revolutionary about this. As an astrophotographer, I know how to take lots of short exposures and stack them to make one frame that easily shows moving objects, comets, asteroids, satellites, etc. There's even a piece of freeware that has "comet mode" where it will take your stack of exposures and find the object that's not moving the same way with respect to the background stars. Same thing...

Re:Amateurs (1)

brainboyz (114458) | about 7 months ago | (#44896081)

Now do that easily and in an automated fashion for an unknown moving object which is scarcely brighter than the noise level and often orders of magnitude dimmer than your reference points (background stars). The amazing part isn't finding a moving object, it's finding a near-invisible moving object in a rather automated fashion.

'standard 5 meter telescope'? (2)

neo-mkrey (948389) | about 7 months ago | (#44895625)

Yes, like the kind you buy on amazon.com, right?

Re:'standard 5 meter telescope'? (1)

K. S. Kyosuke (729550) | about 7 months ago | (#44895713)

I'm sure that in 2085, standard 5 meter telescopes will be available in every corner hardware shop.

Re:'standard 5 meter telescope'? (1)

cusco (717999) | about 7 months ago | (#44897511)

Well, hardware shops with really big shelves in the corner, anyway.

Let's all just agree (1)

sackofdonuts (2717491) | about 7 months ago | (#44895653)

That this is cool. Anything that will help humans identify the source of their ultimate demise is a good thing.

Re:Let's all just agree (2)

bluefoxlucid (723572) | about 7 months ago | (#44895869)

It's cooler than when I read it as "Find millions of nearby assholes" and decided that Craigslist and OKCupid already do this. Or living in Boston or Baltimore, where you just have to look outside.

Re:Let's all just agree (0)

Anonymous Coward | about 7 months ago | (#44902871)

How in the world was parent comment not modded into oblivion as troll?

Talk about an asshole.

Re:Let's all just agree (1)

Therefore I am (1284262) | about 7 months ago | (#44902177)

That given the size of many apartment blocks these days there is the nagging thought that it might be kinder to everyone concerned to just not look for these massively destructive objects until we have an absolutely foolproof way of deflecting them sufficiently to provide a significant engineering challenge for future generations. I sweep dirt under the mat too!

Great news, but may be pointless... (1)

Videospike (2897665) | about 7 months ago | (#44895707)

So now we can find a lot more very dangerous space rocks. That's excellent. However, we can't really do much about them unless we can mass-produce space shuttles, clones of Bruce Willis and Ben Affleck, and crappy Aerosmith songs. But if survival means a world with multiple Ben Afflecks and getting ear-spammed by more sappy Aerosmith power ballads whenever I turn on a radio, we'd be better off with the asteroid impacts.

They weren't doing this already? (1)

vriemeister (711710) | about 7 months ago | (#44895841)

I'm amazed they they weren't doing something like this already. I think its a pretty standard cross correlation filtering method. They even say they're brute forcing it with a GPU, which surprised me. Am I missing something or could this be sped up quite a bit with FFT?

Re:They weren't doing this already? (1)

cusco (717999) | about 7 months ago | (#44897563)

Up until this point it was too expensive computationally. Each set of images require 10^11 computations to process, a non-trivial amount of processing even for a big cluster of GPUs. Asteroids are really, really dim, and small ones are even harder to detect. The signals that they're trying to process are below the noise threshold.

WHAT? (0)

Anonymous Coward | about 7 months ago | (#44896045)

I say again...WHAT?

This is an old technique, and I would have thought they would have been doing this for YEARS!

Those of use in the IT field, know how to come up with some stuff like that, all the time, because we think in a very logical way. For the rest of you scientist; if you are working on any kind of complex problem, or you are simply trying to find a faster or more efficient way, then you need to at least talk to some people in the IT field and get some help. The scientific advancements could be leaping ahead.

Re:WHAT? (0)

Anonymous Coward | about 7 months ago | (#44899021)

Nothing like a boastful coward... Scientists (and militaries) have been using this before there was an IT field. This is applying a brute force search to a well understood idea.

Long and short (0)

Anonymous Coward | about 7 months ago | (#44896203)

Seems as though using an initial long exposure, and finding the streaks that may be NEAs, could inform the search process for the velocities required to align short exposures. It's not as though the NEA trajectory should change after the long exposure was taken.

It is called stacking, and already done (2)

Dr La (1342733) | about 7 months ago | (#44897069)

The more sensitive camera and the algorithm to empirically find the correct direction and speed of movement of a not-known asteroid are new.

The method of overlaying multiple short images so that the asteroid is a pinpoint additive composite of multiple images and the stars become trails is not new.

The latter technique is called "stacking" (a word existing for quite a long time and meaning the same as their "synthetic tracking"). It is regularly done to image and get astrometry on faint objects, when speed and direction of movement are already known (e.g. in follow-up observations on a Near earth Asteroid that already has some observations over the previous hours/days and hence a preliminary orbit). That part is really not new, and there is no need to invent new terminology ("synthetic tracking") for it.

Frankly, it is weird that the authors nowhere mention "stacking" as an existing technique that is often used in imaging faint asteroids. It suggests they did not investigate whether their "new" technique is really that new. Yes, they innovate on it, but they did not invent a completely novel technique.

Re:It is called stacking, and already done (2)

Dr La (1342733) | about 7 months ago | (#44897101)

Small addition: the technique is called "track & stack" when employed on moving objects. Most existing astrometric software can do it.

Re:It is called stacking, and already done (0)

Anonymous Coward | about 7 months ago | (#44899061)

It's not even new to asteroid hunting. See "Detecting Asteroids with a Multi-Hypothesis Velocity Matched Filter",
Shucker, B. D.; Stuart, J. S., Asteroids, Comets, Meteors 2008. I believe it's the exact same technique, deployed by an earlier asteroid search team.

Re:It is called stacking, and already done (1)

Epicaxia (2773451) | about 7 months ago | (#44899917)

This approach appears to be slightly different from traditional frame stacking, in that they are utilizing a low read noise (really, 1e- doesn't pass the smell test--there's got to be some tradeoffs) to take a large number of frames with short exposure times. The only other interesting approach they are taking is searching the velocity space, for which (given 1000 points) they need a 2500-node HPC cluster (you do have one of those in your closet, yes?). From their description, they are also only searching 1px/frame movement, which runs into PSF constraints when the atmosphere starts blurring your crazy-sensitive focal plane (they give a token nod to this problem, and then promise to look into it in a future paper).

There are a couple of items that raised some red flags, including errors in formulating SNR calculations (who measures it in sigma? optical sensor pd--probably of detection--is typically computed for SNR = 6 or 10, in linear space), the avoidance of frame-stacking technique comparisons (as you noticed), and the fact that they conclude with a single-paragraph (5 1/2 lines) consideration of instrumental effects (everything depends on your sensor performance, noise, and sensitivities) while telling us to wait until yet another paper to straighten the issues out.

Of course, I'm being overly critical. I'm actually looking forward to seeing what this approach can do, given that everyone's pretty much given up on characterizing this class size of asteroids in the past. 90% of what they are saying is actually consistent with theory, it's the practice bit where the red flags are going up. It's worth keeping in mind, though, that you don't publish CalTech papers and get time on the Palomar 200" by being a dim-witted slacker.

Re:It is called stacking, and already done (1)

Dr La (1342733) | about 7 months ago | (#44900043)

It's worth keeping in mind, though, that you don't publish CalTech papers and get time on the Palomar 200" by being a dim-witted slacker.

True. I think their presentation of things is more the result of current publishing demands: useful or even innovative is not good enough anymore to get your paper through, it needs to be "new" and "never done before" instead of an innovation on an existing technique.

Still, I find the complete lack of any reference to even the words "track & stack" weird, given that tracking & stacking is common practise in imaging faint asteroids. Maybe not when you use a 5-meter telescope, but with with smaller instruments it is often done. I have used the technique myself o faint asteroids and much-used astrometry packages like Astrometrica have a standard option for it.

Amateur Astronomers have been doing this for years (0)

Anonymous Coward | about 7 months ago | (#44897661)

Credit where credit is due.

The most common open source software used for this is called REGISTAX, and it was developed by a Dutch amateur astronomer in 2001. Google it. Amateur telescopes are often small, so they have much fainter images than the professionals, and they developed their own method of making them brighter.

It sounds as if JPL have just heard about this, and decided to use the same technique. Sensible, but hardly ground-breaking.

Re:Amateur Astronomers have been doing this for ye (1)

wagnerrp (1305589) | about 7 months ago | (#44898979)

Credit where credit is due.

It's called inverse synthetic aperture imaging, and people have been doing it for decades prior to 2001. The difference here is they're doing a brute-force search to discover the motion vector, rather than knowing what it is from the beginning, but then even that's not a new concept. It's merely a concept that is only recently possible due to increases in computational power.

I see a page of wtf... here (1)

flayzernax (1060680) | about 7 months ago | (#44897901)

This is a simple and nifty idea and it works.

Good now we can find those small ez to mine rocks nearbye. Or use those rocks for other purposes... build your habitat directly in one.

I see things have changed (0)

Anonymous Coward | about 7 months ago | (#44899527)

since I lapped my 12" mirror for my telescope.

"They say synthetic tracking has the capability to spot 80 new near Earth asteroids each night using a standard 5 metre telescope."

standard.

5 metre.

what a brave new world...

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