NASA Pinpoints Lightning The Old-Fashioned Way

ke4roh writes: "As a child, I would watch a lightning flash and count the seconds until I heard the first clap of thunder. Get three kids counting in different places, and you could figure out where that cloud-to-ground strike was by coordinating their counts. That's the premise behind NASA's latest lightning detector, according to a press release. It uses a radio to detect the strike and four microphones spaced about 20 feet (7 m) apart. The neat part is its accuracy - about 15 feet (5 m) within a 1 mile (1.6 km) radius. The information should help them determine if lightning may have damaged sensitive launchpad equipment."

Comments

How it works

[ke4roh]

Actually, the microphones don't have to be directional. First, the antenna picks up the radio noise of the lightning strike, then some time (measured) elapses, and the first microphone receives the signal. At that moment, you know the lightning struck on a circle of appropriate radius around that one microphone.* Wait a fraction of a second, and another microphone hears it. You can then draw another circle around the second microphone, and it overlaps the first in only two places. Wait until the third microphone picks it up, draw your third circle, and they will only overlap in one place. Add another microphone for increased accuracy, and you're done. The microphones could be in any configuration, but the farther apart they are, they more accurate the results can be.

* Try this at home: Count the time until lightning arrives. It's about 5 seconds per mile (3 seconds per kilometer), so divide the number of seconds by 5 and you get the lightning's distance in miles (by 3 for km). If you know the distance to the lightning (without the direction), you know that the lightning struck somewhere on a circle with that radius and you at the center.

[BTW: For more unit conversions than you can shake a stick at, visit Russ Rowlett's Units of Measure site which helped me check the numbers above.]