in the range safety circuits caused the launch to be canceled. Countdown was reset that night and proceeded, with several holds, planned and unplanned, from 11:08 p.m., through the early morning of the next day. At 9:21:23 a.m. on July 22, 1962, Mariner 1's Atlas-Agena lifted off from Pad 12. Soon after launch, the booster began drifting northeast of its planned trajectory. Corrective steering commands were sent to the rocket, but the Atlas-Agena instead proceeded further off course, imperiling North Atlantic Ocean shipping and/or inhabited areas in the event of a rocket crash. At 9:26:16 a.m., just six seconds before the Agena second stage was scheduled to separate from the Atlas, at which point destruction of the rocket would be impossible, a range safety officer ordered the rocket to self-destruct, which it did. Cause of the malfunction Because of the gradual rather than sharp deviation from its course, JPL engineers suspected the fault lay in the flight equations loaded into the computer that guided Atlas-Agena from the ground during its ascent. After five days of post-flight analysis, JPL engineers determined what had caused the malfunction on Mariner 1: an error in the guidance computer logic combined with a hardware failure. The hand-written guidance equations contained the symbol "R" (for "radius"). This "R" should have had a line over it ("R-bar" or R̄), denoting smoothing or averaging of the track data coming from an earlier calculation. But the bar was missing, and so the computer program based on those equations was incorrect. This was not an error in programming, but an error in the specification. During its ascent, Mariner 1's booster briefly lost guidance-lock with the ground. Because this was a fairly common occurrence, the Atlas-Agena was designed to continue on a preprogrammed course until guidance-lock with the ground resumed. When lock was reestablished, however, the faulty guidance logic caused the program to erroneously report that the "velocity was fluctuating in an erratic and unpredictable manner", which the program tried to correct for, causing actual erratic behavior, which prompted the range safety officer to destroy the rocket. The incorrect logic had previously been used successfully for Ranger launches; it was the combination of a programming error and a hardware fault which led to Mariner's destruction. The catastrophic effects of a small error "summed up the whole problem of software reliability" and contributed to the development of the discipline of software engineering.