Suddenly, Buzz and Neil heard the high-pitched sound of the Master Alarm. On the computer display the “PROG” light glowed amber. “Program alarm,” Armstrong radioed. Quickly, Aldrin queried the computer for the alarm code, and “1202” flashed on the display.
Lunar Module computer DSKY
Top-Steve Bales. Jack Garmin below receiving award from Alan Shepard & George Low
Lovell toggled the “master arm” switch to On and glanced around to see if everything else was in order. Guidance control was set to “Primary Guidance”; thrust control was on “Auto”; engine gimbals were enabled; the propellant quantity, temperature, and pressure looked good; the ship was maintaining the correct attitude.
Kraft wanted to fire the descent engine now, get the ship back on its free-return slingshot course, and when it emerged from behind the moon and reached the PC+2 point, execute any maneuvers that might be required to refine the trajectory or increase its speed.