US Navy's High-Resolution Radar Can See Individual Raindrops In a Storm | Hacker News Reader

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

networkworld.com

72 pointsTomAnthony29 comments

As someone in the field, the only thing that really stood out about this radar was it's incredibly small beamwidth(.22 degrees compared to a normal .8-1 for most weather radars), and it's incredibly small range gates(.5 meters compared to the 20 meters my radar operates at). That having been said, if this isn't a dual polarization radar, which it sounds like it isn't, then this is still significantly behind the state of the art.

The trend has been to move to higher frequency, lower power radars at X, Ku, and Ka band. Also modern weather radars transmit both H and V polarizations allowing us to measure the shape of the raindrops as well as retrieve full drop size distributions. See http://www.casa.umass.edu/main/research/ and http://pmm.nasa.gov/science/ground-validation/D3R as examples of newer systems.

So why are we spending all this money on "stealth" fighters if essentially other advanced countries like Russia can certainly have similar technology.

because there's other countries then russia

That Russia and China doesn't sell their radar to? Name one?

Stealth is just more dollars for the industrial war complex, especially if they are just going to switch to an army of remote control drones now.

Let's swap the military and NASA budgets for just one year.

Neither Russia nor China tend to sell their latest hardware.

It bugs me when I see this. Neil deGrasse Tyson is asking to double NASAs, budget as if that would be the best place to have money spent on science research.

NASA was the answer to last century's space race. Throwing money at it is an old, simple solution. I'd love if people came out with more ideas like the x-prize. I can get behind those new ideas.

Edit: and it's not like the military doesn't spend a ton of money on scientific and space research

Because that's how arms race's work. It's how all competition everywhere works.

What makes you think this radar is any good at picking up an aircraft like the F-22?

But it may be great detecting small drones, however.

Filtering out all the noise, I suspect, is 'the hard part'. One would have to detect objects in a point cloud and determine if their paths are 'organic/random' such as animals - versus those that take more direct paths...

The article doesn't mention anything about the physical dimensions or the power requirements, but I wonder if putting this on a mobile platform would be at all practical. It's one thing to put them on common storm paths, but imagine aiming a few of these at different axis at a tornado. Being able to analyze the motion of individual bits of debris in a tornado would teach us a lot, I think.

> 3MW power

So "not small" at a guess.

That figure is almost certainly the peak pulse power, not the actual supply requirements. Modern radar almost all operate by firing very very short pulses at relatively low repetition rates[1]

I don't know about the system in question (and if it's still a prototype, it's going to be bigger than it could be), but I think I've heard of systems with similar pulse power being installed in (fighter) aircraft.

[1] https://en.wikipedia.org/wiki/Pulse_repetition_frequency

Fighter nose radars are still in the kilowatt range. Those systems are also rather light (~700lbs all totaled, not counting coolant). There may be pylon-mounted systems that get to the upper end of that (>100kW). High power airborne radars are typically carried by larger, purpose-built platforms such as the E-2C, E-3, and E-8.

The radar they are using is a component of the ballistic defense network. Unfortunately, there are a lot of 'mid-course radars' in those schemes. On a hunch, I think they're referring to this one http://www.globalsecurity.org/space/systems/sbx.htm.

It is mounted on a semi-submersible platform.

Will this help in detecting stealth aircraft since modern stealth aircraft have signatures of large insects (http://en.wikipedia.org/wiki/Stealth_technology#Measuring)?

Still need to distinguish between a large insect and a plane having the signature of a large insect. Otherwise you'd have a lot of false positives.

If it can track it continuously, I imagine speed will pretty much clear up any confusion.

Yeah, continuously is the point here. The frequency of the data points is largely dependent of the distance to the object. And you need to be able to identify the object in two subsequent images.

I guess there's not that many insects at high altitudes either.

Can't imagine that would be terribly difficult. They don't move like large insects for sure.

You'd think in that case one large insect would move a lot faster than the other.

Seeing stealth aircraft isn't about resolution. The key to seeing something with radar is signal-to-noise ratio. From the article:

"it becomes possible to measure the properties of individual raindrops greater than 0.5mm in diameter due to the low concentration of such drops in naturally occurring cloud systems and the overwhelming dominance such drops have on the measured radar reflectivity when present in a field comprised of smaller particles."

It's easy to distinguish an airplane from something with a similar sized signature, say an insect, since the airplane moves at 1000knots instead of 1, but you have to be able to see it through the noise. That's tricky. If you use a radar like this (high power, really narrow beam) you might be able to see a stealth plane. But, you'd have to know where to point it. Therein lies the challenge.

Specifically, article says the search volume is 14 m^3 -- a cube about 8 feet on each side.

There are a lot of such cubes in, say, the airspace over a large city.

Interestingly, there have always been radars able to see stealth planes, e.g. the Tamara radar used to shoot down the first-gen F117 over Serbia.

But they could only pick it up when the aircraft was right on top of them, too late to launch SAMs. The method they used to down that aircraft can only really work if you already know where it is.

So this is what they're letting us know about...imagine what they're working on now.

Is this a "bug" that is being marketed as a "feature"?

It's great that you can see individual raindrops, but with radar, I'd think you'd want to filter the raindrops out.

> It's great that you can see individual raindrops, but with radar, I'd think you'd want to filter the raindrops out.

Article says it was developed to spot stuff falling off the Space Shuttle during launch, so no.

PHP gets the spear, but objective-c gets a pass? I'm not a PHP dev, but at least I can look at it and understand it.

Beauty is in the eye of the beholder I guess.

Hah, how'd this get posted here! Sorry.

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