h a l f b a k e r yWhat's a nice idea like yours doing in a place like this?
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Background info:
The Keck interferometer connects two Keck telescopes in Hawaii. The interferometer works like this: if one telescope sees something that the other does not, that spot is "subtracted" from, and it will get dimmer. It a spot is on both telescopes, the spot will be amplified. This adds
resolution of the telescopes, and makes their resolution equal to the size of a (US-American)football-field size aperture.
Now, apply this to doppler radar. This technology is used to see weather systems. The problem sometimes is, the radio wave will bounce off nearby buildings, thus creating noise.
If we take two doppler towers, which are a certain distance apart, and connect them to an interferometer, calibrate it, and the noise of nearby buildings is reduced, and resolution will be increased.
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Annotation:
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I thought they were already using interferometry in Doppler radar? |
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Yes, it is used. Interferometry is used in longwave imaging systems, to ensure a clear image. |
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The problem you are referring to, [Akabaka], is more often described as ground clutter, which is usually removed electronically, using both automated error removal software and interferometry (as are bird flocks and aircraft). It is usually the result of stray radio waves reflected off artifacts within short range of the installation, giving random, non-contiguous images. I'm certain that work is being done to remove ground clutter and "sea return" which is clutter off wavetops. |
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There is also a rare condition that crops up on clear, still nights, that refracts RADAR waves into the ground around the array, producing very intense false images (I can't remember what it's called... AP, for something or other). |
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Most of the imagery you see on weather RADAR is a composite of Base and Composite Reflectivity, where BR pinpoints the location and CR is used to generate a picture of the intensity of returns. |
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Weather RADAR equipment usually only sends for about 7 seconds in every hour (at about 1300 cycles per second), so there's plenty of time left for listening and reprocessing, which is why the images are so good, these days. |
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[UnaBubba] Do they use two towers, two emitters on the same tower, or what? |
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As I understand it they use one emitter, but obtain about 1300 samples in a second. Their software datestamps each data capture then matches multiple images against each other, to create an electronically generated facsimile of interferometry. |
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Apparently they have been doing something similar with Doppler topographical mapping, from the space shuttle. |
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