Apollo 15 15 separated from the booster, the S-IVB maneuvered away, and would impact the Moon about an hour after the crewed spacecraft entered lunar orbit, though due to an error the impact was away from the intended target. The booster's impact was detected by the seismometers left on the Moon by Apollo 12 and Apollo 14, providing useful scientific data. There was a malfunctioning light on the craft's service propulsion system (SPS); after considerable troubleshooting, the astronauts did a test burn of the system that also served as a midcourse correction. This occurred about 028:40:00 into the mission. Fearing that the
Apollo PGNCS Two PGNCS alarms (1201 "No VAC areas available" and 1202 "Executive alarm, no core sets") were relayed to mission control on the first lunar landing attempt on July 20th 1969. The computer system overload was caused by the simultaneous capture of landing radar data and rendezvous radar data. Apollo PGNCS The Apollo Primary Guidance, Navigation and Control System (PGNCS) (pronounced "pings") was a self-contained inertial guidance system that allowed Apollo spacecraft to carry out their missions when communications with Earth were interrupted, either as expected, when the spacecraft were behind the Moon, or in case of a communications failure. The