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US Navy's High-Resolution Radar Can See Individual Raindrops In a Storm 161

Posted by samzenpus
from the needle-in-a-haystack dept.
coondoggie writes "The U.S. Naval Research Laboratory (NRL) researchers said recently that a Navy very high-resolution Doppler radar can actually spot individual raindrops in a cloudburst, possibly paving the way for new weather monitoring applications that could better track or monitor weather and severe storms. According to an NRL release, the very high-resolution 'Mid-Course Radar' was used to retrieve information on the internal cloud flow and precipitation structure. The radar was previously used to track small debris shed from the NASA space shuttle missions during launch. 'Similar to the traces left behind on film by sub-atomic particles, researchers observed larger cloud particles leaving well-defined, nearly linear, radar reflectivity "streaks" which could be analyzed to infer their underlying properties,' NRL stated."
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US Navy's High-Resolution Radar Can See Individual Raindrops In a Storm

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  • by melted (227442) on Friday June 29, 2012 @04:07AM (#40491271) Homepage

    Their Stealth technology has been obsolete since before they came out, as long as you can use a heavy-ass ground (or ship) based radar system. Russian S400 "Triumf" deals with stealth just fine, and so does S300 with minor mods. And by "deals" I mean shoots down stealth aircraft from beyond its missile range. That's why we haven't attacked Iran yet. That's not the point of stealth. The point of stealth is that _other planes_ can't see you, and you can take them out from way beyond _their_ radar range.

  • by Hadlock (143607) on Friday June 29, 2012 @05:28AM (#40491531) Homepage Journal

    My friend's dad worked for the radar department at Raytheon for about 35 years. He always told us about this radar array in the panhandle of Texas. The power sent out from the radar array was so high that flocks of geese flying in formation would fly through the field, suddenly would become disorientated and fly in different directions, sometimes crashing in to the ground, effectively scrambling their brains. Once they got out of the field, they would return to normal and form up again. Eventually someone got on to them about this and they would shut down the array briefly when geese were detected. Reportedly you needed to wear special eye wear because the radiation could cook your eyeballs like eggs if you weren't careful (your eyes and testes have not many blood vessels and have trouble regulating their temperature compared to the rest of the body). There are stories about beached whales due to navy sonar tests too, but this is a discussion about atmospheric radar.
     
    Anyways, my point is, you start beaming enough energy through the atmosphere and you can have some unwanted effects. I'm sure the aluminum frame of a Cessna 172 acts as enough of a Faraday Cage against these sorts of things, but with your balls literally on the line, do you really want to test out that theory? ;)

  • by bmo (77928) on Friday June 29, 2012 @06:00AM (#40491715)

    They claim they can see a rain drop out to 2 kilometers.

    Fine. Let that be our upper limit for angular diameter. We shall use the largest rain drop of .005m (5mm, but .005m for the sake of units) mentioned earlier to figure this out. We shall then use the angular diameter to figure out how far a golf ball has to be to be the same apparent size (angular diameter).

    Using the large raindrop is our best bet for reality. It keeps us from pushing out the golf ball sphere to ridiculous distances.

    Here, let's do some math.

    Since unicode sucks here, it goes like this:

    Angle = 2 x Arcsin(radius of sphere divided by distance)

    For a flat circle, it's an arctan but we're not using a flat circle. At this distance and size of targets, it doesn't make much difference, but we're using the correct formula for formality's sake.

    Angle = 2x Arcsin(.0025 / 2000m)

    0.000143239 degrees, or about .5 seconds (take number, multiply by 3600)

    A golf ball is 42.67mm in diameter at a minimum, but let's just truncate this for simplicity and readability, and the error makes the radius of detection smaller. .042m/Sin (.00000413239/2) = 1164km

    1164km = maximum effective range to detect a steel golf ball with this radar as long as you can detect the signal (for clarity, I am omitting signal strength and inverse-square law and what it does to detector size).

    But then you say "read the article"

    >With such small pulse volumes, it becomes possible to measure the properties of individual raindrops greater than 0.5mm

    Their minimum raindrop is 1/10 smaller in diameter than the one used in this post. If I had put in .5mm in for calculating angular resolution, I would have pushed out the steel ball 10x the distance, a credulity straining distance.

    Stealth is toast. It is obsolete.

    QED.

    Note: Please do not confuse angle of detection with beam width.

    --
    BMO

  • Correction. (Score:5, Informative)

    by bmo (77928) on Friday June 29, 2012 @06:09AM (#40491747)

    I said .042m/Sin (.00000413239/2) = 1164km

    This is wrong.

    I forgot to use the radius of the golf ball, which is .021

    Which gives 582km instead, not 1164km

    --
    BMO

  • The point of stealth is to take out their radar sites. People declare that it's easy for radars to detect and shoot down stealth aircraft, but how easy is it for a stealth aircraft to blow up a radar site? I have to point out that no one has figured out how to make a stealth radar site yet. Think about this: the radar beam has to travel to the target, reflect, then travel back to the radar site to be detected by the radar. If the target has a bunch of antennas, it can detect the radar much earlier than the radar can detect it.

    In any war, drones and cruise missiles will be the vanguard of the strike force. The UAVs will fly in to draw fire and jam radars, and cruise missiles will be used to hit anti-aircraft batteries that fire. Sure, in theory the radars can detect stealth aircraft but what about a real electronic warfare environment where we have jammers, target drones, and cruise missiles lighting up any radar site that turns on? The B-2 has its own electronic warfare suite, and as seen above, it can see radar sites much earlier than the radar sites can see them. And don't make any mistake: the radar sites are well within the reach of many of our aircraft. The S400 has a maximum engagement range of 400 kilometers. That is well within the range of the JSOW-ER with a small jet engine that can hit targets from 300 nm. The JASSM-ER has a range of 575 miles, which can be deployed by the B-2.
    The B-2 carries the Joint Standoff Weapon (JSOW), which can hit targets from 60 nautical miles. There's a Small Diameter Bomb that can float 60 nmi. Any guy who turns on his radar will have a bad day, guaranteed.

The meta-Turing test counts a thing as intelligent if it seeks to devise and apply Turing tests to objects of its own creation. -- Lew Mammel, Jr.

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