Set SCE to AUX

November 14th, 1969 a cold front was passing through Florida,bringing unstable weather in the form of showers and thunderstorms. At the time of the launch there was no rain in Kennedy Space Center, sky was overcast with clouds between 2,000 and 10,000 feet asl. Weather was considered favorable for launch.

That rainy November day in 1969, at precisely 16:22:00 UTC, the mighty Saturn V rocket ignited her five F-1s engines, delivering a lift-off thrust of 7.5 million pounds. Weighing in at 6.5 million pounds, the fully-fueled Saturn V departs the launched gantry on the sixth crewed flight in the United States Apollo program and the second to land on the Moon. On board were here crew Apollo 12 Commander Charles "Pete" Conrad, Lunar Module Pilot Alan L. Bean and Command Module Pilot Richard F. Gordon.

The Saturn V rocket cleared the tower and at T+14 seconds in, mission responsibility shifted from the Cape to Mission Control Center in Houston, Texas.

The Saturn V booster finished the yaw maneuver, then continued to roll for a launch azimuth of 72 degrees, towards the Atlantic. At T+33 seconds, an ebullient Pete Conrad declared the roll program complete...when a sudden crackle filled the air to ground radio loop.

As the Saturn V booster was passing through an overhanging cloud layer, lightning had struck the Saturn V stack only 36.5 seconds after liftoff.

T+ 00:00:37 Gordon: What the hell was that?
T+000:00:38 Conrad: Huh?
T+000:00:39 Gordon: I lost a whole bunch of stuff; I don't know...
T+000:00:40 Conrad: Turn off the buses.

"The flight was extremely normal... for the first 36 seconds then after that got very interesting"

Pete Conrad

The Master Alarm sounded, Caution and Warning panel on on the Main Display Console lit up, yellow caution lights for all three fuel cells and both main direct current electric power buses and both alternating current power buses were on
indication all electric power generation and distribution systems had suffered a total failure as the Saturn V continues to climb under the 7,500,000-pound thrust from its five F-1 engines.

At T + 52 seconds - second bolt of lightning struck the climbing Saturn V Stack.

T+000:00:56 Conrad: I just lost the platform.
Altitude, a mile and a half [nautical], now. Velocity, 1,592 feet per second.
T+000:01:00 Gordon: All we've got's the GDC.
T+000:01:01 Conrad: Yes.
T+000:01:02 Conrad: Okay, we just lost the platform, gang. I don't know what happened here; we had everything in the world drop out.
T+000:01:08 Carr: Roger.

The "ISS" warning light came on signifying that the inertial guidance system was now in an error state and unable to sense their acceleration and attitude changes. GIMBAL LOCK indicated that the computer had sensed an unacceptable status of the inertial platform as Conrad watched the instrument in front of him spinning aimlessly. NO ATT Inertial guidance system was gone... no longer feeding meaningful info to monitor their attitude during the ascent. The massive Apollo stack including the command module and her spacecraft's crew, had completely lost its bearing and position in space, during one of the most hazardous phases of the mission.

Flight controller John Aaron was watching his screen back at Mission Control when he recognized a pattern in the seemingly entirely random numbers on his screen. He recalled something similar during a test of the Command Module when an anomaly had caused similar figures to be displayed in the data output. According to Aaron, the values displayed after the lightning strike were identical to those he had encountered before.

GRIFFIN (FLIGHT) - How's it looking, EECOM? (...) EECOM, what do you see?
AARON (EECOM) - Flight, EECOM. Try SCE to AUX.
GRIFFIN (FLIGHT) - Say again? SCE to AUX?

000:01:36 Carr: Apollo 12, Houston. Try SCE to Auxiliary. Over.
000:01:39 Conrad: Try FCE to Auxiliary...

000:01:41 Conrad: What the hell is that?

Flight controller John Aaron amazingly recalled a simulated anomaly concerning an obscure system called Signal Conditioning Equipment (SCE), and remembered normal readings could be restored by putting the SCE on its auxiliary setting.

“Flight, try SCE to ‘AUX'”,... but nobody knew what the heck he was talking about.

000:01:43 Carr: SCE, SCE to auxiliary. [Long pause.]
000:01:45 Conrad (onboard): Try the buses. Get the buses back on the line...

000:01:48 Bean (onboard): It looks - Everything looks good.
000:01:50 Conrad (onboard): SCE to Aux.

Apollo astronaut Alan Bean remembered the location of the SCE switch, flipped it to auxiliary, and all Telemetry was immediately restored. The warning lights dimmed, the alarms went quiet and the Apollo crew returned to their tasks at hand.  That single switch saved the entire mission.

All thanks to Flight controller John Aaron...

On November 19th, the crew of Apollo 12 finished thier 230, thousand mile journey to our moon.  Separating ways from the Command Module, Conrad and Bean achieved such a precise lunar landing at their planned location in the Ocean of Storms, that they were literally within walking distance of the Surveyor 3 robotic probe, which had landed on April 20, 1967.

.