After the P22 landmark tracking, Collins had initiated a manoeuvre to orient the docked vehicles to enable Eagle to calibrate its abort guidance system (AGS). As he waited for this to finish, he noted that there was an advantage to being behind the Moon, as they then were, “It’s nice and quiet over here, isn’t it?’’

“You bet,’’ agreed Aldrin.

On finishing the manoeuvre, Collins nulled out the rates and then went ‘free’ while Eagle performed the calibration. After five minutes Collins asked, ‘‘How’s the Czar over there? He’s so quiet.’’

‘‘I’m punching buttons,’’ replied Armstrong, referring to the DSKY activity.

A few minutes later, Collins, having been thinking ahead, urged, ‘‘You cats take it easy on the lunar surface. If I hear you huffing and puffing, I’m going to start bitching at you.’’

“Okay, Mike,’’ Aldrin promised.

During the calibration, the only tasks that could be performed were those that would not induce vibrations. One permissible operation was to open the helium valves to pressurise the DPS propellant tanks. Once the calibration was finished, Collins called, “I’m going to manoeuvre to the undocking attitude.’’ He aligned the docked vehicles ‘vertically’, with the CSM beneath. “How about 100 hours and 12 minutes as an undocking time? Does that suit your fancy?’’

“That’ll be fine,’’ agreed Armstrong.

‘‘Are you guys all set?’’ Collins asked, as the clock ticked down.

‘‘We’re all set when you are, Mike,’’ Armstrong confirmed.

‘‘15 seconds,’’ called Collins. He released the capture latches. If these were to fail to release, the design allowed for a suited crewman to manually release them, either by Collins pulling a handle or by a LM crewman pushing a button on the tip of the probe; in either case, the cabin would require to be depressurised and the appropriate hatch opened to gain access to the mechanism. The latches, however, did release. As the residual air in the tunnel escaped, it made the vehicles slowly drift apart.

Since it was desired that the LM remain in the orbit resulting from the LOI-2 manoeuvre, the parameters of which had been precisely defined by Manned Space Flight Network tracking, the same state vector had been loaded into both vehicles and as soon as Eagle was free Armstrong cancelled the 0.4-foot-per-second rate of separation that the PGNS indicated had resulted from the undocking.[23]

‘‘I’ve killed my rates, Mike,’’ Armstrong announced, ‘‘so you drift on out to the distance you like and then stop.’’

When Collins was about 65 feet away, he halted to station-keep.

Meanwhile, in the Aldrin home, son Andrew wondered aloud why NASA had not installed a communications satellite to relay while the spacecraft was behind the Moon.[24] In the Collins home, Joe and Mary Engle were looking after the children. Pat Collins, flight plan on her lap, was eager for AOS to find out if the undocking had occurred. Jan Armstrong was also at home with her flight plan, thinking the same thoughts.

‘‘Eagle. Houston. We’re standing by,’’ called Duke as the vehicles appeared on revolution 13.

‘‘The Eagle has wings,’’ replied Armstrong.

Collins had installed his 16-millimetre Maurer in window 4 to document this part of the mission. On the flight plan, the television camera was to have been set up

alongside it to provide ‘live’ television, but about 57 hours into the translunar coast Houston had cancelled this telecast owing to the lack of an available channel on a geostationary satellite to relay the transmission from the Madrid receiving station to Houston for conversion. In any case, as Collins had said shortly prior to LOS, he was too busy to set up the television system. The loss of ‘live’ views of Eagle in flight was a disappointment to the national television networks, which had hoped to use it to introduce their uninterrupted coverage of the next phase of the mission.

Several minutes into the near-side pass, Armstrong yawed Eagle around and pitched it up in order to place it ‘side on’ to Columbia, and then slowly yawed it through 360 degrees to enable Collins to visually confirm that the legs had fully deployed and the probes were in position. An unusual sound late in the translunar coast had prompted Armstrong to speculate that the hinged panel on the right side of the vehicle had prematurely deployed, but Collins confirmed that this was in its stowed configuration. ‘‘You’ve got a fine-looking flying machine,’’ he assured.

‘‘See you later,’’ promised Armstrong, as the separation manoeuvre loomed.

‘‘You guys take care,’’ said Collins. With his spacecraft oriented apex-up, he fired his forward-facing RCS for 8 seconds to impart a downward radial thrust in order to withdraw at 2.5 feet per second, during which time the rendezvous radar mounted on Eagle’s ‘forehead’ tracked Columbia as a test of the radar’s ability to lock onto the transponder on the other vehicle, and Columbia tested its VHF ranging apparatus; these tests being designed to verify the rendezvous systems prior to Eagle entering the descent orbit. The separation burn occurred about 10 degrees east of the landing site, and placed Columbia into an equi-period orbit with its perilune 90 degrees later, and some 5 nautical miles lower.

Meanwhile, at home

Astronauts cycled back and forth between the Armstrong and Aldrin homes, as indeed did their wives, although rarely together because their efforts were divided between the families – it was a routine that Jan and Joan understood, as they had done the same thing themselves, and there was no need to play host because it was a self-organising process.