Apollo 11 was four minutes into its landing sequence when the terse words of its commander, Neil Armstrong, came from the speaker in Mission Control:
"Program alarm."
Buzz Aldrin, sitting next to Armstrong in the descending Lunar Module, stared at the frozen display on the computer, which read "1202." It was an error code, but for what? Controllers in Houston scanned their notes trying to figure out what the heck the problem was. But time was running short