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

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 It is obsolete.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

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/H3WbKXwFRao/us-navys-high-resolution-radar-can-see-individual-raindrops-in-a-storm

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