Electronics: Signatures in the Sky

Though the Russians reveal no details about their satellites before they are launched — and precious few afterward — they cannot keep their secrets for very long. Soon after a Soviet space craft has gone into orbit, U.S. Air Force scientists not only record its speed and plot its orbit but determine its size and shape and often deduce its mission. Their spatial detective work is made possible by radar signature analysis (RSA), a little-known technique that may some day be used to save the U.S. from a sneak attack.

With RSA, scientists can reconstruct the characteristics of a...

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