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

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."

Comments

useful....

[ushere]

means you can avoid individual rain drops and keep your battleship dry.....

Re:useful....

[rtb61]

What it means is stealth is now meaningless technology, paying megabucks for a stealth fighter is simply throwing the tax payers money away. Once you can accurately track moisture in the atmosphere, then tracking ex-stealth aircraft is simply a matter of searching for and pinpointing areas of the sky not behaving like other areas of the sky. Specifically those areas of the sky which show a disturbance of where the aircraft has been, contrails http://en.wikipedia.org/wiki/Contrail and where the aircraft actually is shock and compression waves http://en.wikipedia.org/wiki/Shock_wave, even subsonic compression of the atmosphere by the passage of an aircraft substantially alters the amount of moisture in close proximity to the aircraft.

The US Navy might as well announce to the world, don't waste your money on the F35 or F22, what you want is a high durability aircraft. Stealth is utterly meaningless especially when the shape impacts durability and performance. Basically the only real defence is flying really low, as fast as possible and being the smallest target possible (cruise missile). Once you get above ground clutter, you'll announce your position, even if you stop and hover, your past passage will show up as well as your thrust plumes, jet or propeller.

No such thing as 'atmospheric' stealth no matter how advanced your technology unless of course you can jam or shut down the detection technology with even more 'advanced' technology (you can guess who I mean), the microchip being such an desirable target for at range energy fluctuations.

Re:useful....

[tnk1]

This may not yet be useful for real-time air defense purposes. The actual equipment my not be field mobile. Not to mention that getting data and analyzing over time it is one thing. Doing that while an aircraft comes at you at Mach 1.2 is a little different. Especially when it has a bomb or an anti-radiation missile with your name on it.

Re:useful....

[Baloroth]

Scientists could detect the individual particles because of a combination of the radar's3MW power, narrow 0.22 degree beamwidth, and an unprecedented range resolution as fine as 0.5m. This combination of radar attributes allows researchers to sample a volume of cloud about the size of a small bus (roughly 14 m3) when operating at a range of 2 km.

In other words, if you know where the stealth aircraft is to within the region of a small bus, this thing can find it!...so long as it isn't more than 2km away.

This radar is completely worthless in finding a stealth aircraft, or any aircraft at all for that matter. As presented, it doesn't even have any uses for that at all. Maybe you could extend it to that, but the narrow bandwidth and high power means it will be pretty well worthless for stealth detection.

An obvious BOFH bonus

[sunwukong]

"Boss, I'll need some special equipment to see our data in the cloud ..."

How many raindrops are there in a storm?

[evilsofa]

How many raindrops are there in a storm?

So much for stealth

[Melkman]

If you can detect indvidual raindrops, I suspect detecting a marble sized radar target flying near or over the speed of sound is no problem whatsoever. While this radar is probably too big to put in a fighter a datalink from a ground based version to the fighter will solve that problem quite nicely.

Re:So much for stealth

[Chrisq]

Detecting a stealth aircraft and being able to identify what you've detected as a stealth aircraft are two completely different animals.

I think that any "marble sized" object travelling near mach-1 would be suspicious

Re:...Under what circumstances?

[Hadlock]

Might as well karma whore this myself, because someone else is going to, here's a brilliant quote from HHGTTG:

Rob McKenna had two hundred and thirty-one different types of rain entered in his little book, and he didn't like any of them.
 
Since he had left Denmark the previous afternoon, he had been through types 33 (light pricking drizzle which made the roads slippery), 39 (heavy spotting), 47 to 51 (vertical light drizzle through to sharply slanting light to moderate drizzle freshening), 87 and 88 (two finely distinguished varieties of vertical torrential downpour), 100 (postdownpour squalling, cold), all the sea-storm types between 192 and 213 at once, 123, 124, 126, 127 (mild and intermediate cold gusting, regular and syncopated cab-drumming), 11 (breezy droplets), and now his least favorite of all, 17.

Rain type 17 was a dirty blatter battering against his windshield so hard that it didn't make much odds whether he had his wipers on or off.
 
And as he drove on, the rain clouds dragged down the sky after him for, though he did not know it, Rob McKenna was a Rain God. All he knew was that his working days were miserable and he had a succession of lousy holidays. All the clouds knew was that they loved him and wanted to be near him, to cherish him and to water him.

Their Stealth technology has been obsolete since b

[melted]

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.

Re:...Under what circumstances?

[Hadlock]

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? ;)

Re:Military Obsolescence.

[bmo]

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.

[bmo]

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

RTFA: the /. header is non-sensical

[cpotoso]

Unless you have a radar wavelength smaller than the size of a raindrop (\lambda 0.5 mm seems far-fetched), then you CANNOT SPOT INDIVIDUAL RAINDROPS. Furthermore, to achieve the kind of ANGULAR RESOLUTION required, would necessitate a HUGE-sized dish given that roughly speaking the diffracion limit is \Delta \theta ~ \frac{\lambda}{D}, where D = diameter of the dish. What the article says is that you can understand the size and distribution of MANY small raindrops in a cloud, which presumably before you could not. I am amazed how little basic physics /.-tters seem to know.

Re:Their Stealth technology has been obsolete sinc

[darkmeridian]

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.