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Radar Guns Primed For Asteroid Spin Trap

Soulskill posted about a year and a half ago | from the sorry-officer-i'm-late-for-work dept.

Space 23

astroengine writes "During the flyby of asteroid 2012 DA14 on Friday, radio astronomers will be priming their antennae to do some cutting-edge science on the interplanetary interloper. After firing radio waves at the space rock, the Karl G. Jansky Very Large Array (VLA) will work in tandem with several dishes that make up the Very Long Baseline Array (VLBA) to detect the reflected signal, radar gun style. But they're not measuring the object's speed. They're actually going to gain a measure of DA14's spin, a quantity that relates to the physical mechanism of the Yarkovsky Effect — the impact that solar heating has on the long-term trajectory of asteroids."

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23 comments

I just hope (-1)

bobthesungeek76036 (2697689) | about a year and a half ago | (#42887481)

they do an episode of Big Bang Theory based on this event!

Re:I just hope (0)

Anonymous Coward | about a year and a half ago | (#42887649)

"big bang" and "asteroid flyby" shouldn't be used in the same sentence.

Re:I just hope (1)

eksith (2776419) | about a year and a half ago | (#42887783)

Naturally. If there was a miscalculation during the flyby and there's an impact, it's a Small Bang.

Re:I just hope (1)

SilentStaid (1474575) | about a year and a half ago | (#42888291)

Naturally. If there was a miscalculation during the flyby and there's an impact, it's a Small Bang.

That's what she said. /duck

Re:I just hope (0)

Anonymous Coward | about a year and a half ago | (#42888607)

hold on.. (1)

hartek451 (971580) | about a year and a half ago | (#42887897)

So a supposed 'rock' takes a quick look at us, and we open fire with Elderdeath weapons? Wars have started that way...

A new attempt to balance the budget (3, Insightful)

Grayhand (2610049) | about a year and a half ago | (#42888005)

They figure given the asteroid's speed the cost of the speeding ticket could balance the budget.

Re:A new attempt to balance the budget (1)

bobthesungeek76036 (2697689) | about a year and a half ago | (#42888045)

<quote>They figure given the asteroid's speed the cost of the speeding ticket could balance the budget.</quote>

Brilliant!!!! Now the only problem is who to send the ticket to...

Re:A new attempt to balance the budget (0)

frosty_tsm (933163) | about a year and a half ago | (#42888267)

<quote>They figure given the asteroid's speed the cost of the speeding ticket could balance the budget.</quote> Brilliant!!!! Now the only problem is who to send the ticket to...

According to Fox, we are becoming a godless nation so... God?

Re:A new attempt to balance the budget (1)

steelfood (895457) | about a year and a half ago | (#42888511)

Separation of Church and State dictates that dieties cannot be ticketed or otherwise held accountable for their (mis)deeds by the government.

Re:A new attempt to balance the budget (0)

Anonymous Coward | about a year and a half ago | (#42889627)

Separation of Church and State actually implies that Church and State are separate entities and could bill or ticket each other.

Re:A new attempt to balance the budget (1)

steelfood (895457) | about a year and a half ago | (#42888453)

$195 billion is hardly a dent in our national debt.

awesome opportunity here (0)

Anonymous Coward | about a year and a half ago | (#42888257)

This is coming so close to Earth it is unbelievable. Don't we have a couple of old satellites that we could fire up and try to catch up and orbit this? Hint: maybe a milsat. Might as well go out in a flame of glory than just rust in space. The Japanese recently reprogrammed an idle satellite to do something outside of its planned mission.

Re:awesome opportunity here (2)

dietdew7 (1171613) | about a year and a half ago | (#42888439)

I would have said it's inconceivable.

Re:awesome opportunity here (1)

cusco (717999) | about a year and a half ago | (#42890765)

No, satellites only have small thrusters to keep them in the correct orbit and occasionally dodge debris. It would have to accelerate enormously in order to get close to the speed this thing is moving at in relation to Earth. About the best they could do is perhaps put something in its path and watch the 'splat'. That would in fact be interesting, but I don't know of any plans to do so.

Bad reading is bad (0)

Anonymous Coward | about a year and a half ago | (#42888277)

I read the headline as "Radar Guns Primed for Asteroid Spinal Tap", which - let's be honest - sounds way more exciting. Those radar guns go to eleven.

Look at the girly man... (0)

Anonymous Coward | about a year and a half ago | (#42890795)

...afraid of a flying rock!

Are they using synthetic aperture radar... (3, Interesting)

Ungrounded Lightning (62228) | about a year and a half ago | (#42891749)

... of the "rotating target" variety?

Back in the '60s I was working on a project involving using synthetic aperture radar to resolve rotating objects (including NON-rotating objects that were orbiting or flying by - giving you a viewpoint from progressively different directions, which is equivalent.)

Reflection of an illuminating "chirp" (long signal with a constant rate-of-change-of-frequency) gives you a return with a frequency shift that tells you the distance to each feature of the target, added to a doppler-shift term telling you how fast it's approaching or receeding. Coherently combining results from a series of chirps lets you separate the two, giving you distance from the unchanging part and cross-range position from the change. Shazam: A two-dimensional map of the object's radar reflectivity, from a viewpoint over the axis of (apparent) rotation. Right-angle inside folds and corners (and some other concave features) retro-reflect like roadside reflectors, too.

We were working on something that could resolve details of a small satellite in orbit, as if you were looking down on it and seeing every corner, fold, and "ding" as if it had a marker light attached. (The project didn't get followed-on and later I figured out why: A picture leaked during the first shuttle flight when they had lost some tiles and were worried about reentry problems: The spooks had a ground-based telescope camera that could read a license plate from that distance. B-b )

Such techniques can resolve objects to amazingly fine detail. Because phase information is preserved the solution is "analytical" - you can resolve far below the wavelength of the illuminating signal. Your resolution limit is more related to the accuracy of your signal data collection and stability of your electronics than illuminating wavelength (actually - frequency breadth of the "chirp").

The basic technique would give you a map as if you were hovering over the object on its axis of (apparent) rotation. You'd have the "northern" and "southern" hemisphere combined - but if the object's (apparent) rotation axis isn't aligned so you're exactly in the plane of its equator, continued observation through more than one rotation would let you separate the two.

Also: You only need ONE antenna, not a long-baseline array of them. The effective "baseline" is the length of the apparent path of the antenna, while it illuminated a given point, as viewed from the surface of the target. This would be FAR larger than the diameter of the earth - essentially the half-circumference of an "orbit" with the distance from the antenna to the target as the radius , i.e. pi * distance to the rock if it makes at least half a turn (from our viewpoint) during the flyby.

This was the sort of thing we could do in the '60s, with rudimentary equipment by today's standards. With half a century of technological advancement I'd expect much better results. B-)

So I hope they're applying this technique, or some improvement of it, to this flyby.

Re:Are they using synthetic aperture radar... (2)

Ungrounded Lightning (62228) | about a year and a half ago | (#42891869)

As the knowledgeable and observant will have noticed: This is very similar to side-looking radar. (In fact, for a flyby of a non-rotating asteroid, with the antenna located at one of the Earth's poles, it would be EXACTLY side-looking radar.)

It just uses a different phase correction and aperture selection on the recorded reflections. We did it on the same equipment, with a slight change to the post-processing arrangement.

Re:Are they using synthetic aperture radar... (0)

Anonymous Coward | about a year and a half ago | (#42892461)

That is the most interesting thing I have read in the past week.

Re:Are they using synthetic aperture radar... (0)

Anonymous Coward | about a year and a half ago | (#42892281)

Your resolution limit is more related to the accuracy of your signal data collection and stability of your electronics than illuminating wavelength (actually - frequency breadth of the "chirp").

I don't really see how that could result independence from a resolution limit. When going beyond the geometric optics and taking the wave phase into account, you can go beyond the Rayleigh criterion (which even itself can be beaten by almost an order of magnitude with good enough data and processing), but other similar limits pop up depending exactly what type of beam you are dealing with. Synthetic aperture lets you either "beat" such limits, or treat the limits as having an aperture much above the geometric size of the antenna, but still comes back to wavelength limits. I'm not familiar with what was state of the art in the 60s, but now a days it is something on the order of a centimeter for airplane to ground distances, trumped in development systems by only going to higher frequency bands.

Also: You only need ONE antenna, not a long-baseline array of them.

You only need one antenna, but the data is very much improved by using multiple antennas over a large baseline.

Re:Are they using synthetic aperture radar... (1)

Ungrounded Lightning (62228) | about a year and a half ago | (#42938723)

Since the baseline is the length of the path of the antenna as observed by the target, and that path is nearly pi times the distance to the target (on which any region is illuminated for up to half a rotation), the separation of earthbound antennas is a small drop in a big bucket.

The data is still improved, of course. (Especially if the separation is at right angles to the path if the Earth is over the object's equator.) But other than that the man improvement comes from things like ability to cancel out (or selectively reject) noise, or more samplesj, not the baseline as baseline.

Re:Are they using synthetic aperture radar... (1)

vandamme (1893204) | about a year and a half ago | (#42899005)

"So I hope they're applying this technique, or some improvement of it, to this flyby."

Yeah, we would have, had we not been BRAC'd. I have a 400 MHz bandwidth chirp exciter/receiver in the closet, if anybody has a radar handy. We used it to image the ISS just for fun, the day before they shut us down.

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