ORBIT REFINEMENT

Collins terminated the orbital rate and adopted an inertial attitude to undertake the P52 platform alignment in preparation for the forthcoming LOI-2 manoeuvre. As a contingency against a total loss of communications, McCandless read up the data for two transearth injection manoeuvres: one in case the LOI-2 burn failed to occur, and the other in case it succeeded and contact was then lost. In both eventualities, the LM would be ditched prior to leaving orbit.

Meanwhile, it had been found that the anomalous decrease in the pressure in the nitrogen tank of Bank-B during the LOI-1 burn had occurred only while the system was active, which prompted the speculation that it was merely a thermal effect that made the orifice of the solenoid valve open wider on Bank-B than on Bank-A, thereby increasing the nitrogen flow rate (in other words, there was no external leak). The engine could be operated in single-bank mode; the dual-bank mode was to provide redundancy against one bank failing and shutting down the SPS. As the pressure of the nitrogen tank in Bank-B was now stable and was well above the ‘red line’ value of 400 psi (below which it would be incapable of holding the propellant feed valves open), it was decided to conserve this tank in order to retain redundancy against the total loss of Bank-A. McCandless relayed the decision to make the LOI-2 burn in single-bank mode using Bank-A, then as they approached the limb he gave the formal go-ahead to attempt the burn. The attitude of the spacecraft placed them ‘heads down’ in order to point the sextant towards space, and once they were on the far side Collins took a star sighting on Denebola to confirm their attitude.

When Apollo 8 and Apollo 10 had executed LOI-2, they had entered more or less circular orbits at 60 nautical miles. However, when the time came to perform the transearth injection manoeuvre, the gravitational perturbations of the mascons had transformed their paths into ellipses ranging between 54 and 66 nautical miles. Although this did not compromise Apollo 8’s objectives, if a landing had been tried on Apollo 10, the ground track would have been displaced several miles from that intended. In the case of Apollo 11, however, it was essential for Eagle to fly on course and, for the rendezvous, for Columbia to be waiting in as circular an orbit as possible. On the previous missions, the longitude of perilune induced by the perturbations had been about 100°E. The flight dynamics team had calculated that if the post-LOI-2 orbit were to have a given ellipticity and a perilune at 85°W, the mascons would tend to circularise the orbit. The option of having Columbia fire its engine to recircularise its orbit shortly prior to rendezvous was dismissed as a waste of propellant. Furthermore, it was arranged that as the Moon slowly rotated on its axis, the plane of the spacecraft’s orbit would drift such that when Eagle made its descent its ground track would intersect the landing site. At the time of the LOI-2 manoeuvre the combined mass of the vehicles was 71,622 pounds. The 17-second burn was to start at 080:11:36, and achieve a retrograde delta-V of 159.2 feet per second for a spacecraft velocity of 5,364 feet per second in order to revise the orbit to 53.7 by 65.7 nautical miles.

As they waited, they entered sunlight, and Collins noticed lots of little bright spots on the LM reflecting the light. ‘‘The poor old LM’s contaminated – it’s got urine particles all over it! By the way the light’s shining, they look yellow. You know, I guess everything else has boiled off and it’s left a little solid deposit.’’

‘‘Wait until the ‘forward contamination’ people hear about that!’’ said Aldrin. ‘‘There will be no more urine dumps on the way to the Moon; those fellows will have to store it all in a nice little bag.’’

Ignition was precisely on time. Collins was timing it using a stopwatch, and if the engine did not shut down on time they would intervene. Even a 2-second over run would slow them sufficiently to cause their trajectory to dip dangerously close to the surface during the near-side pass, but cutoff was as planned. Armstrong asked the computer for the new orbital parameters. “66.1 by 54.4 – you can’t beat that!”

“That’s about as close as you’re going to get,’’ Collins agreed.

With the spacecraft in a 2-hour orbit, Mission Control would receive telemetry for about 75 minutes. This was more than 50 per cent of the orbital period because, at an altitude of about 60 nautical miles, the vehicle was in line of sight for several minutes beyond the 90-degree angle as measured from the centre of the lunar disk.

As before, Armstrong initiated a 180-degree roll, as a preliminary to resuming a pitched-down attitude.

“While this thing’s rolling over, I’m going to take a pee,’’ Collins announced. On venting the urine to space, he pondered how long it would take before its orbit decayed and it struck the surface – more contamination of the lunar environment! As Armstrong began the pitch manoeuvre, Collins noted that they had missed out on a long-lens picture of Earthrise the first time around, and had been too busy the second time. “Gee, it’s too bad that we can’t stop right here and observe the Earth come up.’’

“We probably can do it, if we stop it right here,’’ Armstrong noted. “That is, if you want to spend the gas.’’

“That’s the only trouble,’’ Collins mused, “the doggone gas.’’

“Why don’t we stop it?’’ prompted Aldrin.

“Okay!’’ said Collins.

Armstrong decided to adopt an inertial attitude that would put Earthrise in one of the windows and also enable the high-gain antenna to lock on. In commanding the manoeuvre, he selected the wrong direction. “Oh, son of a gun!’’ he chuckled. “We are going backwards. Oh, well.’’

“Dummkopf!’’ said Aldrin.

“Neil, pitch down,” encouraged Collins.

“Prior planning prevents poor performance,’’ recited Aldrin.

“Is that right, Buzz?’’ asked Armstrong.

“Where’d you ever hear that one, Buzz?’’ Collins demanded.

“I can’t think,’’ said Aldrin.

A few minutes later, Collins exclaimed, “Here’s the Earth. Hey, I’ve got the view over here.’’

John McLeaish, who had taken over as the Public Affairs Officer, informed the waiting world that both Goldstone and Hawaii had acquired Apollo 11 on time, an indication that the burn had gone to plan. During the far-side passage, the shift had changed in Mission Control. Although Milton Windler’s Maroon Team had taken the White Team’s slot in the daily cycle to give Kranz’s controllers a 32-hour rest prior to tackling the powered descent, Charlie Duke had opted to work the coming shift. Armstrong reported that the LOI-2 burn had been nominal. It was all strictly business. For most of this near-side pass there was little communication with the spacecraft. “This pass is fairly quiet,’’ noted McLeaish almost apologetically. “No doubt the crew is occupied with preparations to enter the LM, which we expect to occur over the far side of the Moon.’’ Aldrin was to spend 2.5 hours transferring items into the LM, and methodically configuring the switches in preparation for the next day’s operations.

About 50 minutes into the pass, Duke prompted for a progress report. “We’re wondering if you’ve started into the LM yet?’’

“We have the CSM hatch out, the drogue and probe removed and stowed, and are just about ready to open the LM hatch now,’’ replied Armstrong. And then, a few minutes later, “Okay, Charlie. We’re in the LM.’’

McLeaish observed, “They appear to be a little ahead on their time line.’’

After making the post-manoeuvre P52 platform check, Collins also decided to get ahead by adopting the attitude for the P22 landmark tracking that he was to do on revolution 4 of Alfa 1, the small bright crater on the Foaming Sea, with the objective of measuring its elevation relative to the intended landing site.

During the far-side pass, Armstrong shaved using cream and a razor.

“I see Earth,’’ said Aldrin, as the spacecraft rounded the limb on revolution 4, “but it’s a lousy picture.’’

Goldstone and Hawaii both acquired Apollo 11, and Duke put in a call. Collins told him that he was set up for the P22 landmark tracking. “Ho-hum, ho-hum. I only got set up for this thing about an hour early,’’ he chastised himself, provoking laughter on board. As they flew overhead, Collins made five sightings of Alfa 1 at timed intervals. On completion, he quipped to Armstrong, “Well, that’s one P22 out of the way. Ho, ho, ho!’’ When the sightings were processed, it was calculated that the landmark was 500 feet above the landing site – knowledge that would assist Armstrong and Aldrin to monitor their approach to the point at which they were to initiate the powered descent.

While in the landmark tracking attitude, the spacecraft had been unable to point its high-gain antenna at Earth, and the downlink using one of the omnidirectional antennas was noisy. However, this had no impact because, as McLeaish observed, “So far on this pass we’ve had just one contact with Apollo 11, and that was Mike Collins at AOS.’’

Duke called, “You can proceed to sleep-attitude now.’’

“Let’s hold this attitude a bit,’’ Aldrin prompted Collins, “I want to look at the PDI approach. Man, this is really something. To see our approach into the landing site, you’ve got to watch it through the LM’s window.’’

“Houston,’’ Collins replied, “we’re holding inertial for a little while to study the approach to the landing zone.’’ On looking out for himself, he said to Armstrong, “There go Sidewinder and Diamondback – God, if you ever saw check points in your life, those are it.’’

“But we don’t get to see them,’’ Armstrong noted.

“You don’t?’’

“No, we’re yawed face-up.’’

Since their previous inspection, the terminator line had migrated westward sufficiently to reveal their landing site. “I think I can see it,’’ Aldrin called with delight. “Yes, I can! I’ve got the whole landing site.’’ He depressed his Push-to – Talk, “Houston, this is Eagle. I can see the entire landing area.’’ While this was the first use of the call sign, the communication was via his umbilical to Columbia’s system.

“Roger, Buzz,’’ replied Duke matter-of-factly.

With the Sun barely above the horizon at the landing site, the lengthy shadows were highlighting the topography sufficiently to make the mildest of surface relief appear very rough. “Boy, that sure is eerie looking,” Aldrin mused.

“Isn’t that something?” said Armstrong, viewing from the command module. This was a significant moment in the mission.

“f missed taking a picture of it!’’ exclaimed Aldrin. ft did not matter, he would be able to take one later.

“Shall we manoeuvre to the sleep attitude?’’ Collins asked.

“All right,’’ Armstrong agreed.

Although the LM’s power margin was narrow, the flight plan included a test of its VHF and S-Band radio systems. “Houston, Apollo 11 – Eagle – over,’’ called Aldrin directly.

“Roger, Eagle,’’ replied Duke.

“f’ll go ahead with the sequence camera checkout,’’ said Aldrin. “f’m still on low voltage taps, and f assume there’s no problem doing that.’’

“That’s affirmative,’’ Duke confirmed.

Twenty minutes later, having tested the Maurer 16-millimetre camera, Aldrin announced, “Eagle is powering down. Out.’’

Just after Apollo 11 passed ‘over the hill’ Aldrin rejoined his colleagues, and Collins suggested that they need not reinstall the probe and drogue overnight.

‘‘ft’s okay with me,’’ agreed Armstrong.

‘‘How’s that going to affect sleeping?’’ Aldrin wondered.

‘‘f’d rather sleep with the probe and drogue than have to dick about with them in the morning,’’ Collins insisted. As long as they could squeeze their legs around the hardware stowed under the couches, there ought to be room to sleep. With the decision made, he installed the command module hatch over the tunnel.

‘‘ft’s amazing how quickly you adapt,’’ said Collins. ‘‘ft doesn’t seem weird at all to me to look out there and see the Moon going by, you know?’’ This prompted general laughter.

While Apollo 11 was behind the Moon, Owen Garriott took over as CapCom from Duke for the remainder of the Maroon Team’s shift. On the near-side pass, Collins undertook miscellaneous chores, then prepared their suppers. Over the far side once again, Aldrin, who had stood ‘watch’ the previous night, offered to do so again, ‘‘Why don’t you guys sleep underneath tonight? f’ll sleep top-deck.’’

‘‘Unless you’d rather sleep up top, Buzz,’’ Collins said, ‘‘but you guys should get a good night’s sleep before going in that damn LM. Which would you prefer? fs that probe and drogue going to be in your way over there?’’

Aldrin took a look. ‘‘No, f don’t think so.’’

ft was decided to follow the flight plan, and have Armstrong and Aldrin sleep in the hammocks. ‘‘Well,’’ said Collins, ‘‘f think today went pretty well. ff tomorrow and the next day are like today, we’ll be safe.’’

‘‘We’re ready to go to bed,’’ announced Garriott when the spacecraft appeared around the trailing limb on revolution 6.

‘‘We’re about to join you,’’ Collins replied.

With that, communications ceased. However, prior to retiring, Armstrong and

Aldrin, seeking to ‘get ahead’, prepared the clothing and equipment they would need the next day. Collins had the satisfaction of seeing his crewmen fall asleep before he himself settled down in the left couch.

In Houston, Glynn Lunney’s Black Team took over for the ‘graveyard’ shift, and his flight dynamics team analysed the tracking by the Manned Space Flight Network in order to verify that the spacecraft’s orbit was evolving in the manner designed to counteract the mascon perturbations. On the evening of Saturday, 19 July, Gene Kranz attended a Mass ‘‘to pray for wise judgement and courage, and pray also for my team and the crew’’. The astronauts’ wives endeavoured to find solitude in which to contemplate what Armstrong and Aldrin were to attempt the next day.