AOS

Apollo ll’s troubles began as they came around the Moon’s eastern limb. There had been a major change to the configuration of the lunar module since Apollo 10 had rehearsed the descent orbit. Plume deflectors had been added around the descent stage to protect it from the blast of hot gas from the RCS thrusters and these were now interfering with the radiation pattern of the steerable high-gain antenna. Worse, Armstrong was flying with the windows facing the Moon to gain timings relating to his orbit. This meant that the steerable antenna had to peer past the LM structure. The diagrams that indicated the resultant restrictions and which angles the steerable antenna could use were in error. At acquisition of signal after Eagle had entered the descent orbit, mission control found that not only did this interference make voice communication with the crew difficult, it interrupted the engineering telemetry with which flight controllers would soon make a decision on whether to proceed with the landing.

To try and alleviate the problem, Charlie Duke in mission control passed on a recommendation from Pete Conrad, who was sitting close by, that they yaw the LM right by 10 degrees. Enough data did get through for the Go/no-Go decision to be made positively, though in the event, it had to be relayed via Mike Collins in the command module.