Steve Bales (Guido) made a new entry to the trajectory and guidance section of the rules book which excluded lunar module computer program alarms 1201 and 1202 from the abort list.
Crew training for Apollo 11 was already complicated by the need to master the controls of two different and very complex spacecrafts, as well as the space suit, but now the mission took on new dimensions, principally in learning how to set a 14.5-metric-ton lunar module safely down on the moon.
NASA officials used only 12 words to list the primary objectives of Apollo 11:
1-Perform a manned lunar landing and return.
2-Perform selenological inspection and sampling.
“Hey, Apollo – Houston, this is Apollo 10. Look, I know you ran some studies, but by golly, we can see Snoopy, and he isn’t too far away! He’s catching up with us. Can you talk to the FIDOS? He’s right down below us. We can occasionally see him tumbling end-over-end down below there, and he’s coming in closer each pass. That’s Snoopy’s descent stage. We can see him right down below us now, and he’s right – I thought he was a little out-of-plane, but now he’s looking more in-plane with us.” Tom Stafford Apollo 10
When Stafford and Cernan were ready for undocking they discovered the Lunar Module had slipped three and a half degrees out of line with the command module at the latching point, possibly due to loose mylar collecting on the docking ring…
The six-minute retrograde maneuver seemed interminable, just as it had to Borman’s crew on Apollo 8, but the engine kept firing and the Apollo 10 crew’s confidence in it kept growing. When the engine finally shut down and they were sure that it had done its job, Stafford and Cernan had time to look at the lunar surface. They likened one area to a volcanic site in Arizona. Shortly, Stafford forced his attention back inside the cabin and told his crew-mates that he thought the best thing to say when they got back in radio contact with mission control was, “Houston, tell the earth we have arrived.”
After a shaky but successful S-IVB burn Apollo 10 was on the way to the Moon. Now the first order of business was for John Young to move to the command module pilot seat.
At first stage cutoff the astronauts expected to encounter a single pulse of negative G and the crew would be thrown forward in their straps before the Second stage ignited and recommenced the acceleration. However, they actually encountered a form of pogo which continued for 4 cycles, during which they were “slammed forward, back, forward, back, forward, back, and forward, back. At this point the instrument panel was so blurred the astronauts could not read it.