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"Synthetic Tracking" Makes It Possible to Find Millions of Near Earth Asteroids
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."
How many hedgehogs to an apartment block?
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.
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.
It seems like it would be much simpler to just use optical flow to find moving objects.
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Fuck systemd. Fuck Redhat. Fuck Soylent, too. Wait, scratch the last one.
"Medium.com" is one of those aggregator sites. Don't link to them. Link to the actual paper. 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.
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"
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.
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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?
Yes, like the kind you buy on amazon.com, right?
That this is cool. Anything that will help humans identify the source of their ultimate demise is a good thing.
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.
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?
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?
Yes, but I was thinking "edge detection" which is something different. Conceptually I meant Hough Transform.
Sounds like this http://en.wikipedia.org/wiki/Synthetic_aperture_radar
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.
"I opened my eyes, and everything went dark again"
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.
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.
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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.
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.
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.