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This FAA release, obtained through The Black Vault, collects material on the radar data from Japan Air Lines Flight 1628 over Alaska on November 17, 1986. It includes a March 5, 1987 explanation by FAA public affairs officer Paul Steucke, a February 1987 Airway Facilities memo, and Dennis Simantel's analysis attributing the returns to uncorrelated primary and beacon targets, considered normal. It also contains regenerated radar image photos and a Philadelphia Inquirer magazine article on the sighting and the FAA's inconclusive review.
UNCORRELATED RADAR SIGNALS An "uncorrelated primary and beacon(secondary) return on a radar screen occurs when the radar energy that is sent up toward the aircraft (primary signal) returns off the surface of the aircraft at a slightly different moment than fhe beacon (secondary) transponder signal and the two do not match up as being at the same place or same computer radar cell . --~~~~~~~~111L--~~~~~~~~~ --RADAR COMPUTER CELL, 1/4 MILE-- --,/'- SECONDARY RADAR RETURN (Beacon) (Transponder) --11 FAA RADAR Drawing by Paul Steucke March 5 , 1987 SAME AIRCRAFT (Skin- Surface) RADAR CELL =PRIMARY RADAR RETURN =SECONDARY RADAR RETURN =CORRELATED RETURN (Combined Return) =UNCORRELATED RETURN
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