[T]he moonrise occurred directly in the path of the Thule detection radar, producing a strong signal return. While the computer system never generated an impact prediction, the large amount of data caused enough concern that the equipment was subsequently modified to reject moon returns based on their long (2 second) delay.So where did this come from, anyway? The 1987 CACM paper "Computer system reliability and nuclear war" (full text behind a paywall, unfortunately) claims that there was
a false alert in the early days of the nuclear age [16, 69, 89], when on October 5, 1960, the warning system at NORAD indicated that the United States was under massive attack by Soviet missiles with a certainty of 99.9 percent. It turned out that the Ballistic Missile Early Warning System (BMEWS) radar in Thule, Greenland, had spotted the rising moon. Nobody had thought about the moon when specifying how the system should act.(This was dramatic enough for the editors, or someone at CACM, to use this as a pull quote.) The supplied references, however, cast some doubt on this in my mind. They are:
89. New York Times. Moon stirs scare of missile attack. NPW York Times (Dec. 8. 1960). 71:Z.So, supporting this statement in what is presumably trying to be something along the lines of an academic journal we have, as well as the venerable New York Times, a popular press paperback and the Reader's Digest. Let us pause while we contemplate that last one.
16. Berkeley. EC. The Computer Revolution. Doubleday, New York, 1962.
69. Hubbell, J.C. You are under attack! The strange incident of Octoher 5. Reader's Dig. 78, 468 (Apr. 1961), 37-41.
At any rate, as you can see from the title of the Times article, perhaps it wasn't quite such a scare after all. I don't particularly feel right now like paying $3.95 for the full article, but I presume that, in the newspaper article tradition, the first paragraph is a proper summary of the exciting part of the story:
WASHINGTON, Dec. 7 (AP) -- Radar reflections from the moon set off a missile scare at the nation's air defense centers on Oct. 5. The Air Force said today, however, that its equipment had been adjusted to avert more such flurries.Then again, perhaps the Reader's Digest fact-checking department managed to verify what the New York Times fact-checkers couldn't. I think it's clear which story the CACM went with.
I have now managed to track down the full text of that Times article, and it turns out that the first paragraph truly was the most exciting one. The paragraph following:
Actually, the scare was only momentary, the Air Force said, since a quick check turned up the error.Eventually, we find that even in those heady days of the cold war we had someone rather more level-headed than General Ripper in command:
[T]he commander in Colorado, Gen. Laurence Kuter, had found immediately that the reported detection "was totally unsubstantiated by other information sources and in no way indicated a threat" of missile attack.