"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."

Comments

Is it just me?

[Score Whore]

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?

[edmudama]

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?

[kruach aum]

"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?

[Baloroth]

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?

[Anonymous Coward]

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?

[dogsbreath]

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?

[mdielmann]

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.

STANDARD UNITS, PLEASE

[Anonymous Coward]

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

[oodaloop]

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

[Gilmoure]

Can the mass be measured in '73 Beatles full of Cüe Cats?

Re:STANDARD UNITS, PLEASE

[Virtucon]

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.

Quit spamming for "medium.com"

[Animats]

"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.

Re:Quit spamming for "medium.com"

[vriemeister]

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.

And yet..

[kryliss]

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.

'standard 5 meter telescope'?

[neo-mkrey]

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

Re:Let's all just agree

[bluefoxlucid]

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.

It is called stacking, and already done

[Dr La]

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

[Dr La]

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