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Apollo 8

Day 1: The Maroon Team

Corrected Transcript and Commentary Copyright © 2003 by W. David Woods and Frank O'Brien. All rights reserved.

[The Apollo 8 mission has been flying for six and a half hours and Frank Borman, Jim Lovell and Bill Anders have left the vicinity of Earth, the first time any human has done so. They are headed for a rendezvous with the Moon in about 60 hours time when its gravity will take them around its far side and they will be able to burn their main engine and enter lunar orbit. Having recently separated from the upper stage of their launch vehicle, they now depend only on the systems of their CSM (Command Service Module) for propulsion, food, water, power and anything else in their mini-planet that they need to explore the Moon and get them home.]

[Jim is about to extend a navigation exercise he started but didn't complete to the satisfaction of Mission Control. Delays curtailed a series of measurements of the angle between Earth and a star, and only five such sightings were made. Mission Control would like Jim to add a few more to improve their understanding of how accurately he can mark on Earth's fuzzy horizon. The sightings are made using program 23 in the computer, so the procedure is known as "P23". Key to this exercise is the evaluation of how consistently Jim can use the Earth's horizon as a reference in his sextant observations. An accurate determination of the Earth's horizon is essential for even the most rudimentary estimation of their position and velocity. Because Apollo 8 is still relatively close to the Earth, nontrivial errors are inevitable. As the exact point of the Earth's horizon is still vague, a precise estimation of position is impossible, but is also important to understand how much error can be expected.]

[Apart from a checkout of the spacecraft's High Gain Antenna (HGA), Frank and Bill are settling down for the trip. Once Jim is finished his P23 sightings, Frank can begin rotating the spacecraft around its longitudinal axis in the Passive Thermal Control (PTC) maneuver, or barbecue roll, to even out the extreme temperatures encountered in space.]

[Mission Control, meanwhile, has just undergone a change of shift. The Maroon team, under Flight Director Milton Windler has replaced the Green team headed by Flight Director Cliff Charlesworth. Mike Collins has vacated the CapCom console to be replaced by Ken Mattingly.]

006:32:42 Borman: Houston. Apollo 8. [No answer.]

006:32:52 Borman: Houston. Apollo 8. [No answer.]

006:32:56 Mattingly: Apollo 8, Houston. Did you call?

006:32:59 Borman: Roger. There is the High Gain Antenna on Wide, Auto.

006:33:04 Mattingly: Roger.

[Long comm break.]

[The HGA (High Gain Antenna) can be set to three beamwidths; narrow, medium and wide. It is easier to acquire a signal from Earth when the antenna has a wide beamwidth.]

006:35:21 Borman: Houston, Apollo 8.

006:35:24 Mattingly: Go ahead, Apollo 8.

006:35:26 Borman: Are you getting the results you want from our High Gain Antenna?

006:35:44 Mattingly: Apollo 8, Houston. Affirmative. We are getting your data, and we may have a beamwidth change but stand by on that.

006:35:53 Borman: Alright. We're standing by. Jim's about ready to go back to the P23.

006:35:57 Mattingly: Roger. We have a Go until 7 hours on the start of the PTC.

[This gives Jim 25 minutes to get an extra set of sightings for his navigation exercise.]

006:36:54 Borman: Houston, Apollo 8.

006:36:57 Mattingly: Go ahead, Apollo 8.

006:36:59 Borman: We're on the PTC mode now waiting for Jim, and I noticed that out my window now I can see Orion very clearly, even though the Sun is bright in the other window.

[With the season being winter, the Sun is in the constellation of Capricornus. In other words, a line drawn from the Earth through the Sun aims at this constellation. This is on the opposite side of the sky from Orion, as many skywatchers will testify, for Orion is a prominent winter constellation.]

006:37:14 Borman: It almost pained me to say that, but it's true.

006:37:19 Mattingly: Roger.

006:37:22 Borman: Speaking of the windows, the number 5 window is getting pretty well obscured and the number 3 window is unusable.

006:37:29 Mattingly: Roger. Understand; number 3 is unusable and number 5 is obscured. Can you make out any definition at all, or do you have a target to look at?

006:37:39 Borman: Well, I can see the Sun. Wait till it comes around the Earth, and I'll give you a better hack on that.

[Of their five windows, three are becoming badly fogged up with only the small, forward-facing rendezvous windows remaining clear.]

006:38:14 Mattingly: Apollo 8, Houston. We're going to go ahead and try to dump your tape right now. Circuit margins aren't too good at our present configuration. We're going to take a look at it. If it doesn't work, we may have to dump it again at a later configuration.

006:38:30 Borman: Roger.

[Long comm break.]

[Ken Mattingly is talking about the tape within the DSE (Data Storage Equipment). This tape recorder stores digital data from various spacecraft systems. Mission Control want to replay the data and radio it down to Earth where they can analyse it. To get a clean copy from the tape, the radio link needs to be good and it may not be due to the HGA being set to a wide beamwidth. A narrow beamwidth improves the signal but requires far greater pointing accuracy.]

006:43:02 Mattingly: Roger. Thank you.

006:43:29 Lovell: Houston, this is Apollo 8. I'll do two more sets on [star] 15, and then we'll do one set on [star] 16.

006:43:35 Mattingly: Roger. Thank you.

[Comm break.]

[To complete his navigation exercise, Jim is going to measure the angle between Earth's horizon and firstly the star Sirius, which he should do six times, then with Procyon, which he should do three times.]

006:44:40 Borman: Go ahead, Houston. Apollo 8.

006:44:41 Mattingly: Okay, Apollo 8. I'd like to fill you in on things we're thinking about doing in the next couple of hours, first chance you get there.

006:44:51 Borman: Go ahead.

006:44:52 Mattingly: Okay. In relationship to the midcourse correction, we'd like to put that one off until about 11 hours, and it will be approximately a 25-foot-per-second burn. The reason we're delaying the burn time is to allow for better tracking as a result of the 7½-foot-per-second you put in on the separation. We'd like to take little more time to look at the tracking data. And the dispersions in your correction aren't going to be growing very fast here. What we'll do then is to delete the NAV sightings that occur about 09 plus 10 in the flight plan, and this will be getting us back on to the normal flight plan sequence. So we'll go ahead and finish the P23, and the 7-hour limit on that P23 is due to the range limits on this test. Over.

006:45:46 Lovell: Is due to the... what did you say?

006:45:47 Mattingly: The 7 hours on the P23 problem is due to the fact that we want to get these sightings in at a certain range. Over.

006:45:56 Lovell: Roger. Understand.

[To interpret Mattingly's instructions, Mission Control are going to delay the first midcourse correction by two hours until 11 hours GET. Apollo 8 made a larger-than-planned burn to separate from the S-IVB and the ground controllers would like more time to get information about the resulting flight path before calculating exactly what burn will return them to their desired course. As they are in the early stages of their coast to the Moon, very small errors in their flight path will have profound effects by the time they reach the Moon. They want to see how these errors grow before deciding the size of the burn to correct them.]

[Mission Control have decided to compensate for the delays so far by cancelling a second series of navigational sightings by Jim at 009:10.]

[Ken mentions a 7-hour limit to Jim's first navigation exercise. This is due to the thickness of the Earth's atmosphere becoming less important as their distance increases. Note that the point of this early navigation exercise is to determine how consistently Jim marks at the same part of Earth's fuzzy horizon.]

006:46:06 Borman: No. I think that's fine. We need to get out of the suits and get something to eat here too.

006:46:11 Mattingly: Roger. Looks like we'll be back on the Flight Plan by 11 hours. We'll be holding up on the updates and PADs because of the later burn.

[Comm break.]

[The crew have kept their suits on for an hour or two longer than planned and want to remove them soon. Each suit, known in NASA jargon as a PGA (Pressure Garment Assembly) is stored in a bag for the duration of the mission and will now only be used in the event of an emergency. Bill's suit is on display at the Science Museum, London, United Kingdom.]

[Borman, from the 1969 Technical Debrief - "PGA doffing and stowage were easier in zero g than on the ground. The stowage bag, and I must stand corrected from a previous flight, the stowage bag worked great, fine. It was a proper way to stow the space suits. I would not recommend stowing the space suits under the individual couches because it would be too cramped in there when you tried to sleep. The stowage bag is by far the best procedure."]

[Lovell, from the 1969 Technical Debrief - "Concerning PGA doffing and stowage: you have to be careful not to maneuver too quickly after you get out of the couch. When you first get into orbit, it takes a little while for the body to become acclimated to the zero g environment. You can easily become slightly queazy in the actions if you are not careful to move slowly before you become used to the environment."]

[All later Apollo lunar flights will require some sort of spacewalk (or EVA (ExtraVehicular Activity)), either as an objective or, in case a docking fails, as a contingency and suits will be necessary equipment. However, the suits on board Apollo 8 will never be needed again.]

[Borman, from the 1969 Technical Debrief - "We should re-examine our position on requiring pressure suits for flights that do not include EVA. I would not have hesitated to launch on Apollo 8 without pressure suits. I think that we should. We wore them for about 3 hours and stowed them for 141 hours. I see no reason to include the pressure suits on a spacecraft that's been through an altitude chamber, and we have confidence in its pressure integrity."]

006:47:37 Mattingly: Go ahead, Apollo 8.

006:47:40 Lovell: Roger. I believe we have the S-IVB in sight. It would appear to be tumbling, and every once in a while, we are getting very bright reflections from it off the star - off the Sun.

006:47:51 Mattingly: Roger.

[Comm break.]

[To set it on a course for the Moon's east limb, the S-IVB dumped its remaining propellants and burned its attitude control thrusters to depletion. Now it has no way of controlling its attitude. Since one of its thruster packages burned for longer than the other, the stage has been left with a small rotation. This off-axis firing had negligible effects on the stage's trajectory.]

[Working with Program 23 in the computer, Jim is measuring the angle between the brightest star in the sky, Sirius, and that part of Earth's horizon which is opposite the star.]

006:50:12 Mattingly: Affirmative. Apollo 8.

006:50:13 Borman: Okay.

[Very long comm break.]

007:00:15 Borman: Go ahead, Houston. Apollo 8.

007:00:18 Mattingly: Roger. We're copying your P23 progress. FAO advises that it looks like you are finishing your first star, and we'll need one more set on the second star, and this 7-hour cut-off isn't that firm, so we would like for you to go ahead and complete the second star if you can.

007:00:39 Borman: We're on the last setting of the second star right now.

[Jim is measuring the angle between the star Procyon and that part of Earth's horizon opposite the star.]

007:00:51 Borman: Okay. We'll do them one at the time for about 4 minutes on each of them.

007:00:59 Mattingly: Roger. [Long pause.]

[The fans that stir the contents of the cryogenic tanks have a special place in Apollo folklore for it was the operation of one of these devices on Apollo 13 that initiated that mission's near-tragic abort and return to Earth.]

[CSM 103, being one of the early Apollo Block II spacecraft, has two hydrogen and two oxygen tanks in the Service Module. These gases are stored at high pressure and at cold temperatures. Quantity measurement is achieved by a tube-within-a-tube capacitance gauge. Through time, the gas within a tank begins to separate out into layers of varying density, known as stratification, affecting the accuracy of the quantity readings. To overcome this, fans were installed in the tanks which were operated daily, homogenising the contents and allowing accurate readings of the tank quantities to be taken.]

[During the Moon-bound coast of Apollo 13, oxygen tank two exploded immediately after a cryo stir was begun. Post-flight analysis determined that an electrical fault associated with the fan had started a fire. With abundant oxygen to feed the fire, the pressure rose rapidly, bursting the tank and damaging nearby plumbing.]

007:01:57 Mattingly: Roger, Bill.

007:02:03 Lovell: Houston, Apollo 8. We've just got finished taking two sets, six sightings on Sirius, and one set [three sightings] on Procyon.

007:02:17 Mattingly: Roger. I understand that's six on Sirius and one on Procyon.

007:02:23 Lovell: Two sets on Sirius, one set on Procyon.

007:02:25 Mattingly: Roger. [Long pause.]

007:02:37 Borman: And we're maneuvering now to PTC attitude.

007:02:46 Mattingly: Oh. Roger, Apollo 8. [Long pause.]

[Space is a strange place for those of us used to the warmth of Earth. Here, heat from the Sun is absorbed by the air around us, by the oceans and by the land so as a result, temperatures are moderated. We know instinctively the importance of air in the transportation of heat, whether it is between the sea and land, around the rooms of our houses or within the equipment we possess that must lose the excess heat it generates. In space, things are very different.]

[Imagine we place an object in cislunar space, not too near the Earth, hanging motionless. The side facing the Sun will be warmed. How much depends on its characteristics but as it gradually warms, it also radiates heat. The warmer it gets, the more heat it radiates, eventually reaching a point where it is radiating as much heat as it receives. At this point, it is at thermal equilibrium, its surface temperature is constant and probably quite high. Meanwhile, the side of the object opposite the Sun will also radiate whatever heat it had, but this will not be replenished. The surface temperature will gradually fall until the minimal sources of heat available to it become comparable to the heat it is losing. Given time, and assuming little heat leaks through the object from the Sunward side, this area will become extremely cold. These extremes of temperature easily coexist in an environment where there is no air to conduct heat.]

[In the Apollo spacecraft, there are various reasons why it is undesirable to allow these temperature extremes to exist for long. For example, the heatshield material around the Command Module may crack and flake if it gets too cold, while the propellant tanks for the RCS thrusters need to be kept at moderate temperatures at all times to prevent freezing or overpressurisation. The simple solution arrived at is to gently rotate the spacecraft around its long axis as it coasts between the two worlds, while positioning it side-on to the Sun. This technique is formally known as Passive Thermal Control (PTC). For many commentators, a far more descriptive term is the barbecue mode.]

[The PTC was meant to begin at 005:20 in the Flight Plan, but it has been delayed. Pitch and yaw figures were given there for Frank to maneuver the spacecraft to, which he is now doing. Once there, he initiates a constant, slow roll of only 0.1° per second. At that speed, it takes an hour for the spacecraft to make a complete rotation around its long, or X-axis. However, bodies are not meant to rotate in this fashion, at least not in the long term, especially with large quantities of fluid contained within them. With time, the rotation axis itself rotates until it is roughly perpendicular to the long axis. Therefore, the long axis will sweep out a cone with an ever increasing angle.]

[Borman, from the 1969 Technical Debrief - "We found the barbecue mode to be the most acceptable using a wide deadband for pitch and yaw and minimum impulse for roll. We established a roll rate of about 0.1 degrees per second. It worked very well, and the spacecraft would usually stay in a plus or minus 20-degree cone for half an hour or so before requiring trimming to get back to PTC gimbal angles. We tried Passive Thermal Control without using any rate or attitude hold damping and the spacecraft diverged very rapidly. I believe this would be unacceptable, particularly with the LM/CSM combination."] [It would turn out that this simple method of initiating and maintaining PTC was unsuitable for later missions. The greater length of the stack with the Lunar Module attached made the simple roll maneuver difficult to maintain. Use would be made of the tracking programs in the computer to carefully control overall attitude as the rotation progressed. In particular, the rotation rate would be increased from 0.1° to 0.3° per second.]

[Later during the post mission debriefing, Frank discussed ways of trying to maintain the proper longitudinal rotation. One suggestion had been to look out of the forward-pointing rendezvous windows and maintain the X-axis on a star. However, the stars are easily washed out by the brightness of the Moon, Earth and Sun.]

[Borman, from the 1969 Technical Debrief - "It's difficult to establish, in my mind, any better way of doing it than just using gimbal angles. It would be impossible to monitor out the window on a star and continue to maintain an initial position with any degree of precision out the window because as you rotate or revolve, first the Moon, the Sun, and the Earth wipe out a considerable portion of the sky. It is true you can see stars out the window in the daytime, but this is only when the window is shielded from the Sun, the Moon, or the Earth, and when you are quite a distance from the Earth."]

[The Dim 2 position for the spacecraft lighting brings on secondary lights in the cabin. This increases the power drain from the fuel cells and are not meant for long-term running.]

007:03:47 Mattingly: Okay. Any time you have them on, running Dim 1 position is preferred to the LEB.

007:03:52 Borman: Thank you. [Long pause.]

007:04:39 Anders: Houston. We have the cryo fan on - the number 1 H₂ tank was on at 07:01. You can give us a hack when you want it - when you're ready for it to be turned off.

007:04:50 Mattingly: Wilco. [Pause.]

007:04:57 Mattingly: Okay, Apollo 8. You can terminate that one and go to the other tank.

007:05:01 Anders: Roger. [Pause.]

007:05:10 Anders: Okay. O₂ gauge number 2 is on.

007:05:14 Mattingly: Roger.

[Comm break.]

007:06:22 Mattingly: Go ahead.

007:06:23 Lovell: Are you having any problem on the ground with your comm?

007:06:27 Mattingly: Negative. You're coming in loud and clear.

007:06:30 Lovell: Okay. We seem to be breaking lock intermittently up here once in a while.

007:06:35 Mattingly: Roger. We'll keep our eye on it. It sounds good though.

007:08:46 Lovell: Okay. Houston, Apollo 8. We've initiated the PTC.

007:08:51 Mattingly: Roger. [Long pause.]

007:09:32 Mattingly: Okay. Apollo 8, you can terminate the fans in the hydrogen, and we're ready to start on the oxygen tanks.

007:09:41 Lovell: Okay. Stand by.

[Comm break.]

[By the Flight Plan, the first meal should have been over the last hour, but delays in the separation from the S-IVB have held it back.]

[Readers should note that we have edited the commentary from the Public Affairs Office announcer to take account of how they operated during Apollo 8. Unlike later Apollo missions, where the PAO feed to the press and broadcast organisations was essentially live from the air-to-ground audio, the policy during Apollo 8 was to record a swathe of comm and replay it on the PAO feed immediately afterwards. Therefore, we have mildly edited their commentary to remove the logical inconsistencies where the PAO officer introduces a recording, thereby preserving the thread of this journal. Such editing is marked with ellipsis.]

007:12:02 Lovell: Thank You.

[Long comm break.]

007:15:15 Lovell: Okay.

007:15:19 Mattingly: And for your information, it's Cleveland 24 to 10, and what we plan to do...

007:15:27 Lovell: Say again.

007:15:30 Mattingly: That's Cleveland 24 to 10, not over yet.

007:15:42 Borman: Thank you.

[Long comm break.]

[Ken Mattingly is keeping track of a game of American football for the crew. The Cleveland Browns are playing a home game against the Dallas Cowboys in front of an impressive crowd of 81,497 spectators.]

007:21:31 Anders: Roger. We're doing the program 21 now, determining ground track for LOI that we did not make at 5 hours.

007:21:44 Mattingly: Roger. Thank you.

[Long comm break.]

[The PAO announcer is about to explain to the press a previous tape recording which included a discussion of Apollo 8's fogged window problem. Meanwhile, Jim begins a computational exercise that was first scheduled for 5 hours GET. This is a Ground Track Determination using P21.]

[Program 21 works out the latitude and longitude that will be directly below the spacecraft at a particular time. If Jim uses the program a number of times, entering a different GET each time, he can determine the spacecraft's ground track. The program achieves this by taking the current state vector and working it forward mathematically (using a pre-programmed model of the Earth-Moon system) to the required time. Good results in this exercise require the state vector aboard the spacecraft to be very good as small errors this far away from the Moon expand until they render the result meaningless.]

007:27:20 Borman: Houston, Apollo 8.

007:27:21 Mattingly: Go ahead, Apollo 8.

007:27:22 Borman: Okay. We just broke lock on S-band High Gain. We're on Omni D now.

007:27:29 Mattingly: Roger. Omni B. [Pause.]

007:27:36 Mattingly: Apollo 8, Is that Bravo or Delta?

007:27:40 Borman: Dog. Delta.

007:27:41 Mattingly: Roger.

007:27:43 Borman: We can't get the Program 21 to integrate up to LOI; just stalled out around 61 hours and 2 minutes.

007:28:02 Mattingly: Roger. They are watching it. [Long pause.]

[As Jim operates the computer via the DSKY (Display and Keyboard), flight controllers in Mission Control can see what appears on his displays and therefore monitor his progress. Jim is having a problem and FIDO (Flight Dynamics Officer) is working out why.]

007:28:38 Mattingly: Go ahead, Apollo 8.

007:28:41 Borman: Roger. Do you want us to stop the integration via Verb 96? Over.

007:28:54 Mattingly: That is affirmative; Verb 96.

007:28:57 Borman: Roger. Will do.

[Very long comm break.]

[Verb 96 should stop the program running and send the computer to P00, the "do nothing" program. The computer does not actually do nothing. In truth there are a number of housekeeping tasks it will continue to do; update the state vector, correct the spacecraft's attitude for example. The computer is always "doing something" although these housekeeping tasks are not always obvious.]

007:56:51 Borman: Houston, this is Apollo 8.

007:56:54 Mattingly: Apollo 8, Houston.

007:56:55 Mattingly: Go ahead, Apollo 8.

007:56:58 Borman: Roger. Do you want us to hold off on this P52 realignment, also?

[Regularly throughout the mission, and especially before using their engines, the guidance platform is realigned so that it is oriented in space as accurately as possible. The first midcourse correction has been delayed by two hours and all the activities that are relevant to it need to be similarly delayed.]

007:57:10 Mattingly: That is affirmative, Apollo 8. Let's time the maneuver and we will hold off and do that all in normal pre-maneuver sequence. And - We have got a score here [in the Cleveland-Dallas football game] - in the fourth quarter, 31 to 13. And I've got some words on your P21 discrepancy any time you are interested. And I'd like to confirm...

007:57:30 Borman: Go ahead.

007:57:33 Mattingly: Okay. Before I get off on that one, I'd like to confirm that you use the Verb 37 procedure to go to P00.

007:57:41 Borman: Roger.

[Verb 37 simply instructs the computer to change to another program and is the normal way to go to Program 00. Documentation from the Guidance and Control checklist indicates that Verb 96 should also take the computer to P00.]

[Post-flight analysis of their trajectory is included in the Mission Report on page 5-9. In table 5-III, the best available state vectors that resulted from a maneuver are calculated forward to show the expected time and altitude of closest approach to the Moon. According to this table, their current trajectory as set by their second separation maneuver is too fast and, if uncorrected, would swing them behind the Moon at an altitude of 848.4 kilometres. However, Mission Control are still analysing their flight path and the state vector within the spacecraft's computer is out of date. When P21 calculates it forward, it shows the flight path actually hitting the lunar surface (in a mathematical sense) whereupon, the program refuses to go on working.]

[Ken Mattingly's comment regarding the 'program note' might very well resonate with those readers who support any software application. Even in the 1960s, software vendors maintained documentation of known bugs and programming limitations in their products. It is often said that few if any bugs were discovered during a flight. This is perhaps quite true, but the conditions known to create problems were well documented in program notes. Procedures and mission rules were designed to avoid these problematic situations.]

[Journal reader Tim Blaxland helped me decode this comm. The nitrogen that was in the cabin air at launch was gradually being replaced by being vented overboard. This was done using the Waste Stowage Vent Valve. While cabin air was being vented, a relatively high flow of O₂ was noted by the crew. With the vent closed, the O2 flow would come down to maintain constant cabin pressure.]

007:58:23 Borman: Roger. That's done.

007:58:24 Mattingly: Okay. Thank you.

[As the crew breathe, they exhale carbon dioxide (CO₂). This gas is toxic and its concentration must not be allowed to rise excessively. After cabin air is drawn from the suit circuit (and therefore in this case from the cabin) it is passed through two canisters containing granules of lithium hydroxide and activated charcoal. Lithium hydroxide has the property of absorbing CO₂ from the oxygen atmosphere while the charcoal absorbs odours. After a time, the canisters become saturated, lose their effectiveness and are alternately replaced throughout the flight.]

007:58:33 Lovell: This conference communication is great. We won't have to have any debriefing.

007:58:37 Mattingly: [Laughter] That's pretty outstanding.

007:58:38 Comm Tech: Right. [Pause.]

007:58:43 Mattingly: Did you copy that?

[Very long comm break.]

[All the flight controllers wear headsets and are able to plug into various communication loops throughout the MOCR (Mission Operations Control Room, the proper term for the room where the controllers sit). Only the Crew and CapCom should be able to speak on the air/ground loop. Evidently, one of the other loops has been temporarily connected to the air/ground loop.]

Public Affairs Officer - "This is Apollo Control. At the present time, the spacecraft altitude is 37,749 nautical miles [69,911 km] and our velocity down to 9,800 feet per second [2,987 m/s]. We don't hear any more conversation from the crew. We will stand by to pick up again should any communication develop between the ground and the spacecraft. This is Apollo Control at 8 hours, 04 minutes."

008:13:39 Borman: Houston, Apollo 8.

008:13:42 Mattingly: Go ahead, Apollo 8.

008:13:44 Borman: Roger. With the delay in burn, do you mind if we have a urine dump the - before the burn? Will that foul your tracking up?

[Expelling any substance from the spacecraft imparts a tiny thrust that, over time, can have a large affect on its trajectory. The crew are aware of this and don't want to make a urine dump without checking with Mission Control first. In this case, there is not a problem. Though still working out the size of the next burn, Mission Control are happy that the effects of the urine dump will be minimal. The burn itself will probably introduce some trajectory error anyway but subsequent spacecraft tracking will determine its magnitude.]

008:14:53 Mattingly: Apollo 8, Houston. We don't have any objections to going ahead with the urine dump now. And for your information, the waste water dump - our schedule, we plan to put it off until about 11:30, and this will get you up to approximately 90 percent in your waste tank. It's a little higher than normal, but we wanted to put this off until after the burn was completed.

[As oxygen and hydrogen are combined in the fuel cells to make electricity, water is the happy by-product of the reaction. Though it is very useful as a coolant and for drinking water, more is produced than can be used. This excess is collected in the waste water tank which is regularly discharged to space.]

008:15:40 Borman: Cleveland won over Dallas, huh?

008:15:43 Mattingly: How about that? [Pause.]

[The football match is over. Meanwhile, Mattingly reads up other items coming up for the crew.]

[One of the problems with the fuel cells aboard Apollo is that they are very sensitive to the presence of impurities in the hydrogen and oxygen reactants. To avoid the resultant loss of electrical power this would cause, the cells are regularly purged of contaminants by flushing them with the reactants. Oxygen purges are carried out daily, hydrogen purges are once every two days. Three switches on the LMP's side of the Main Display Console allow Bill to route O₂ or H₂ to any of the three cells for this function. A purge at 9 hours GET is not mentioned in the Flight Plan.]

[From Journal Contriutor Dave Hardin: "A little context on that football game ... This was an early playoff game in the National Football League, the major American football league. The Super Bowl would be played in three more weeks. The Dallas Cowboys have always been immensely popular throughout the U.S. State of Texas, where the crew lived part of the time, of course, even though Houston also had a team. Dallas had 13 wins and only 1 loss going into that day's game with Cleveland, which had 11 wins and 3 losses. Cleveland's win, therefore, was a bit of a surprise as reflected in the comments by Borman and Mattingly."]

[Journal contributor Phil Karn: "'Circuit margin' is the communication engineer's margin for error. It's the difference between the actual signal strength and the minimum required for good communications. You always want a positive margin in case the system performs worse than expected. At 009:47:20, Mattingly says the signal strength is 3-4 dB better than expected on the wide beam antenna and that gives a 1.4 increase in range. Explanation: radio signals, like light, obey the 'inverse square law'. Each doubling of distance weakens the signal by a factor of four. For example, Jupiter at 5 AU from the sun receives only 1/(5^2) = 1/25 or 4% as much sunlight as the earth at 1 AU. A circuit of margin of 3 dB means that the signal is twice as strong as needed. That would permit a distance greater by a factor of the square root of two. The square root of two is about 1.4."]

008:16:56 Borman: Roger.

[Long comm break.]

008:24:26 Mattingly: Loud and clear, Apollo 8.

008:24:29 Anders: Roger. Sure got a nice view of the Earth from here. We can see Baja California and about where San Diego ought to be.

008:24:40 Mattingly: Very good.

008:24:44 Anders: I can't see my dad's flag pole, out there today, though.

008:24:48 Mattingly: We'll tell the doctors about that.

[Very long comm break.]

Public Affairs Officer - "At the present time the spacecraft is approaching 40,000 [nautical] miles [74,080 km] in altitude. We're about 39,500 [73,150 km] and the velocity continuing to drop off down now to about 9,600 feet per second [2,930 m/s]. At 8 hours, 35 minutes into the mission, this is Apollo Control."

008:48:40 Mattingly: Apollo 8, Houston.

008:48:43 Borman: Go ahead, Houston.

008:48:45 Mattingly: Okay. We dropped off of High Gain on the Omni there for a bit and went to a low bit rate, and we're getting ready to command you back to a high bit rate. Do you want us to keep you posted every time we change tape speeds?

[The speed of the tape recorder can be changed under command from Earth.]

008:49:08 Mattingly: Roger. Understand; but when we go to high bit rate, do you want to be kept informed every time we transfer? We hadn't planned on it.

008:49:20 Borman: If we think if we need to record, we'll ask you on that deal.

008:49:24 Mattingly: Okay.

[Very long comm break.]

[The 80-mm lens on their Hasselblad camera has a specified field of view of 38° from side to side.Some time about now, frames AS08-16-2595 and AS08-16-2596 are taken of Earth and based on a quick measurement of the image size, The planet's apparent angular size is about 8.5°. This roughly works out that it was taken at an altitude of about 78,000 km.]

009:09:34 Borman: Apollo 8.

009:09:37 Mattingly: Go ahead.

009:09:44 Borman: Roger. How does your tracking look on us?

009:09:44 Flight Director: FIDO, FLIGHT.

009:10:13 Mattingly: Apollo 8, tracking still in progress and a little too soon to give you a firm answer on the results, but everything looks nominal so far.

009:10:26 Anders: Is it working okay?

009:10:28 Mattingly: Seems to be.

[Comm break.]

[Tracking of the spacecraft is achieved by closely monitoring two characteristics of the S-band radio signal used for spacecraft communications; its Doppler shift and its delay. First, an overview of the radio signal.]

[On Earth at the tracking station, a radio signal is generated whose frequency is very precisely known (2,106.40625 MHz). This is achieved with help from a stable frequency standard on site. This signal provides the carrier for all communication going up to the spacecraft (the uplink). The spacecraft does not generate its own radio carrier for the downlink. Instead, it synthesizes a carrier by multiplying the received frequency by 240/221, resulting in a downlink frequency of 2,287.5 MHz which the tracking stations can lock on to. However, the velocity of the spacecraft will affect the precise frequency received on Earth. This is the Doppler effect, widely used in science to remotely measure velocity, from speeding cars to distant stars. Taking into account the 240/221 change, engineers on Earth compare the received and transmitted frequencies, which yields a very accurate measurement of the spacecraft's velocity along the line of sight. The fact that this is measured over both the up and down legs of the signal's journey doubles the sensitivity of the system.]

[The second tool in the tracker's kit is a measurement of delay which yields the distance (commonly known as range in Apollo parlance) between the spacecraft and Earth. At the tracking station, a pseudo-random digital code was added to the uplink carrier signal. The spacecraft preserved this as it synthesized its downlink carrier, thus sending it back to Earth, where it was compared to the transmitted code. Engineers would 'slide' one over the other until they matched. This would give a time for the round trip, and hence distance.]

009:12:07 Anders: Go ahead.

009:12:09 Mattingly: Okay. Sometime when it's convenient for you now, I would like to see an oxygen fuel cell purge. And do you have any estimate on when you might be getting around to this comm test?

009:12:24 Anders: Right now we're right in the middle of trying to get something to eat, Ken. We can - I guess we can do the fuel cell purge.

009:12:36 Mattingly: Apollo 8, there's no rush. Just didn't know what you were doing at the time and - Give us a call when you have a free moment; we'll pick up.

009:12:50 Anders: We can start the O₂ purge now, if you wish.

009:12:57 Mattingly: Okay. That'd be fine, and I'll keep track of the time for you.

009:13:00 Anders: Okay. That'd be good. Now I'll turn on O₂ now on fuel cell 1.

009:13:05 Mattingly: Okay. Thank you.

[Comm break.]

009:15:47 Borman: Roger. It's up, and number 2 is on now.

009:15:50 Mattingly: Roger.

[Comm break.]

009:17:33 Mattingly: Houston. Go ahead.

009:17:35 Lovell: While I'm waiting for my turn at the water gun, I might give some comments on the optics. There seems to be quite a band of light that goes all way across the scanning telescope anywhere in the vicinity of the Sun. Just a little while ago we were in the position where I could pick up the Moon in the scanning telescope. And then I looked at it in the sextant and the sky - the space around the Moon was a very light blue, just about as light blue as we have it back on Earth. And it's not black - that Sun angle with the Moon.

[Jim is waiting to have his meal, for which he needs the water gun to inject hot or cold water into his dehydrated food bags. While he is talking, the O₂ purge of fuel cell 2 is completed and fuel cell 3's is begun.]

009:18:25 Lovell: That's affirmative. I maneuvered the optics so I could pick up the Moon in the sextant, and the - the space around the Moon is light blue.

[Apollo 8 is travelling to the Moon at a time of the lunar month which will duplicate lighting conditions that future landing missions will see at the planned landing site. Apollo flies across the Moon from east to west with a landing occurring soon after sunrise to give distinct shadows with the Sun at their backs which will improve piloting and reduce the heat load from a lunar surface going from extreme cold to baking hot. Since the favoured landing sites are toward the eastern side of the lunar disk, the Moon will still be a crescent when they arrive. Therefore, at this time, the Moon presents a very thin crescent to the spacecraft and therefore appears to be very near the Sun. As happens with most optical systems, allowing the Sun to fall on lens elements induces much flare.]

009:18:46 Lovell: Well, it extends the full length of the sextant. Actually, I could see us coming as we moved across, because the band of light in the scanning telescope cut across where the Moon was, and it moved in this area. I believe it's caused by the refractional light inside the optics themselves.

009:19:05 Mattingly: Roger.

009:19:09 Lovell: Also, I've been occasionally looking out to see if I could see stars at various Sun angles, and at this particular attitude, it's very difficult. In the scanning telescope the Sun is very bright and the Earth is very bright, And if I looked at the Earth and try to look for stars, I lose my dark adaptation very quickly.

009:19:35 Mattingly: Roger. Do you have any problems seeing the Moon?

009:19:41 Lovell: No problem seeing the Moon. When I looked for the star/landmark line-of-sight, I - It's a very thin crescent, but it vas very visible.

009:19:53 Mattingly: Roger. Does the area illuminated in Earthshine show up?

[When the Moon lies roughly between the Earth and Sun, its night-time hemisphere faces Earth. By the same token, the daytime hemisphere of Earth faces the Moon and is bright enough to gently illuminate the darkened lunar surface. This is easily seen from Earth on the few days before and after a New Moon and is called "Earthshine" or the "Ashen light". Another term is "The Old Moon in the New Moon's arms." by virtue of seeing the bright crescent wrapped around the dimly lit face of the Moon.]

009:20:17 Mattingly: How about that.

009:20:23 Borman: Maybe we have an atmosphere around the Moon. [Long pause.]

[Lovell, from the 1969 Technical Debrief - "I had to use Program 23 by turning the shaft by trunnion to Sirius and then use Sirius for the first sextant calibration. There was a lot more light scatter in the scanning telescope than I had believed there would be prior to flight. At first this appeared to be the case at almost any attitude. In many occasions the light appears as a bar or a shaft across the scanning telescope - a horizontal shaft. At other times it appears as random light, either on one portion of the sextant or scanning telescope. During the first star sightings, the Earth had a very indistinct horizon. The line-of-sight filter appeared to help define it clearer, more than I had been lead to believe. It appeared that the sharpest line of the first sightings, about 4½ hours from the Earth, was actually the junction between the Earth and the horizon area, the atmospheric area. The area where the atmosphere fades into space was very indistinct. It was very difficult to find a good horizon to place a star on. My first view of the Moon appeared as a light blue thin crescent through the telescope which I happened to get by chance. The space around the Moon appeared light blue. I could not see the night side of the Moon. I might add that the light blueness of the area around the Moon was due to the Sun which was near vicinity and caused scattered light through the optics and caused the space around the Moon to appear blue."]

009:21:16 Anders: Roger.

[Very long comm break.]

[The PAO announcer then plays a tape that includes Jim's comments about the optical system to the press.]

[We would add a health warning to the PAO announcer's statement of the vehicle's weight. While in coasting flight, the spacecraft is, of course, weightless and he ought to be using the term "mass".]

009:44:45 Mattingly: Go ahead, Apollo 8.

009:44:47 Borman: Do you want to get started here around 10 hours? Is that what you said?

009:44:54 Mattingly: Well, what we had planned was to use the 10- to 11-hour period as your pre-burn preparation just as we would have done normally, and...

009:45:04 Borman: That's fine. We can go ahead and do that.

009:45:13 Mattingly: ...and if you can work in this comm check before that, it would be desirable, but that's not a constraint.

009:45:20 Borman: What do you want in the way of a comm check, George?

009:45:27 Borman: Again, what do you want?

009:45:29 Mattingly: Okay. What we've got here is a couple of DTO [Detailed Test Objective] comm checks. We'll be switching around to five different modes, and only one of them will interrupt your activities. In that case, we'll be switching to the uplink backup voice, and that's the one time that you might lose temporary uplink voice comm. You'll have downlink voice comm throughout the entire procedure, and it ought to take you, I guess, 10 to 15 minutes max., the only requirement being that we should stay on a High Gain Antenna.

009:46:05 Borman: Why don't we go ahead and start now then?

009:46:07 Mattingly: Okay. That sounds pretty good.

009:46:08 Borman: ...whenever.

[Comm break.]

009:47:46 Borman: Roger. Let's not increase it by 1.4 more, though.

009:47:50 Mattingly: Okay. [Long pause.]

[In other words, even though the comms system should work nearly one and a half times further out from Earth than planned, Frank has absolutely no intention of finding out the hard way.]

[Mission Control want to determine whether the heat from the Sun tends to evaporate whatever is fogging up the windows. Though they expect the fogging to be the same as was experienced during Apollo 7, if it were due to moisture within the panes, it would be possible to change their procedures to clear the windows if needed. However, the substance that is outgassing and fogging the windows is not affected by the Sun's heat and if anything, it scatters sunlight, making the problem worse.]

009:49:04 Mattingly: Okay, Apollo 8. I'm sorry. Would you say again, please?

009:49:08 Borman: The Sun doesn't seem to have any effect on the windows themselves, but the different incidence - angles of incidence of the Sun rays change the relative amount of obscuration caused by the fogging.

009:49:24 Mattingly: Okay. [Long pause.]

009:50:05 Mattingly: Okay, Apollo 8. We're ready to go into the comm check now, and it's your option. We can call out switches and let you position them, or we can command it from the ground. In either event, there will be a couple of switches that you'll have to throw for us.

009:50:24 Borman: We'll have to command them, and we'll throw [the switches] what we have - what you want.

009:50:29 Mattingly: Okay. And I'll keep you posted on what we're doing. The first test is an uplink voice and ranging with full downlink voice which is essentially what you're doing right now, is to be used for a baseline.

009:50:44 Borman: Roger. [Long pause.]

009:51:12 Mattingly: Okay. We're starting on test number 1, and if you would verify that S-band Normal mode switch is in Voice.

009:51:22 Borman: Roger. We're in Voice.

009:51:24 Mattingly: Okay.

009:51:25 Borman: [Garbled] Charlie. [Pause.]

009:51:31 Mattingly: And the Up Telemetry Data to Data.

009:51:36 Borman: Roger. Data. [Long pause.]

009:51:49 Mattingly: Okay. And Up Telemetry Command to Normal.

009:51:55 Borman: Normal.

009:51:57 Mattingly: Roger. How about High Gain Antenna Track to Auto.

009:52:04 Borman: We're on Omni D now; we've got to wait 'til we get around the other way.

009:52:10 Mattingly: Okay. What's your estimate? [Pause.]

009:52:19 Borman: We're at 15 minutes from it.

009:52:25 Mattingly: Okay.

009:52:34 Borman: Maybe we'd better hold the comm check till after the midcourse, because we'd better get fired here at 10 [hours] if we want to burn at 9 [means 11 hours].

009:52:43 Mattingly: That's affirm. We're viewing that right now.

009:52:47 Borman: ... means we're on two vertical level.

009:52:55 Mattingly: Okay, Apollo 8. We're postponing the comm test until after the burn.

009:53:02 Borman: Thank you.

[Comm break.]

009:54:35 Mattingly: That's negative, Apollo 8. We would like to update things first, and we're going to give you a LM state vector and then an external Delta-V.

[Frank is asking whether Jim can proceed with the realignment of the guidance platform that was scheduled at 8 hours. Mattingly points out that there are two tasks required of Mission Control that were originally planned for just before 8 hours and that these should be done first. Both require that the controllers on the ground directly access the computer's memory, first to place a state vector in the LM slots. This is likely a version computed on the ground this Jim can use to compare with the version he will generate during his sightings. Second, they want to do a target load in which they send up time of ignition of the burn (T_ig) and the change in velocity required by the burn, the Delta-V.]

009:54:44 Mattingly: And with P00 and Accept, why, we'll go ahead and work on that.

009:54:50 Borman: Roger.

[Comm break.]

[Mission Control cannot access the computer's memory unless the crew set things up properly. They place the computer in program 00 (the do-nothing program) and throw the Up Telemetry switch from Block to Accept.]

009:57:20 Borman: Go ahead.

009:57:22 Mattingly: Okay. We've got your PADs. We're ready to read up to you. And we're standing by to uplink your state vector and external Delta-V whenever you're ready to give us Accept.

009:57:36 Borman: Roger. Just stand by one, and we will get the PAD from you. [Pause.]

009:57:48 Borman: And we will put in - TM [Telemetry] in Accept now - at this time.

009:57:53 Mattingly: Roger. [Long pause.]

009:58:10 Borman: We're ready to copy the PAD. [Pause.]

009:58:21 Mattingly: Okay, Apollo 8. I didn't copy that last one. We are sending your state vector up now.

009:58:26 Borman: Roger. We say we are ready to copy the PAD.

009:58:29 Mattingly: Okay. The first PAD will be a maneuver PAD, MCC-1: and this will be an SPS/G&N beginning with the weight; 63295; minus 1.63, plus 1.29; 010:59:58.30; plus 0013.6, minus 0004.5, plus 0020.2; 345, 188, 343; 99999; plus 0168.5; 0024.8, 0:02, 0018.6; 23, 201.3, 16.4; 012, up 27.6, left 0.4; November Alpha for the remainder of that column. In the comments: north stars; 068, 097, 356; a no ullage start, and a single bank burn on bank Alpha. Over.

[The PAD is interpreted as follows:

Purpose: This PAD is for the first midcourse correction en route to the Moon.

Systems: The burn will be made using the large SPS (Service Propulsion System) engine at the rear of the Service Module, under the control of the Guidance and Navigation system.

CSM Weight (Noun 47): 63,295 pounds (28,710 kg).

Pitch and yaw trim (Noun 48): -1.63° and +1.29°. These are the angles through which the SPS engine should be swivelled to ensure its thrust acts through the spacecraft's centre of gravity.

Time of ignition (Noun 33): 10 hours, 59 minutes, 58.30 seconds.

Change in velocity (Noun 81), fps (m/s): x, +13.6 (+4.1); y, -4.5 (-1.4); z, +20.2 (+6.2). The change in velocity is resolved into three components measured relative to the Local Vertical/Local Horizontal.

Spacecraft attitude: Roll, 345°; Pitch, 188°; Yaw, 343°. The desired spacecraft attitude is measured relative to the alignment of the guidance platform. This would be oriented to the launch pad REFSMMAT.

Just as apogee and perigee refer to the high and low points of an orbit around the Earth, the terms apocynthion and pericynthion are similar. Strictly speaking, they refer to the high and low points in a lunar orbit for a spacecraft that was launched from Earth. For a spacecraft launched from the Moon, the equivalent words are apolune and perilune. As Apollo 8 was launched from Earth, we will continue to use the former terms in this journal.

H_A, expected apocynthion of resulting orbit (Noun 44): The figure of 99999 really means there isn't a meaningful apocynthion as their resulting trajectory would bring them around the Moon and back to the vicinity of the Earth.

H_P, expected pericynthion of resulting orbit (Noun 44): 168.5 nautical miles (312.1 km). This figure seems rather high and we suspect a transcription error. However, we need to check it with the audio tapes as it is repeated in the transcript during Frank's readback. We suspect the figure should be 68.5 nautical miles (126.9 km). Three pieces of evidence support this: One, this is around the pericynthion altitude they would be targeting for. Two, the post-mission report includes a table on page 5-9 that gives the pericynthion calculated from this burn as 66.3 nautical miles (122.8 km). Three, after the burn, at 012:27:01, Jim uses the spacecraft's computer to calculate their pericynthion and gets an answer of 67.4 nautical miles (124.8 km).

Delta-V_t: 24.8 fps (7.6 m/s). This is the total change in velocity the spacecraft would experience. (It is a vector sum of the three components given above.)

Burn duration or burn time: 2 seconds. Note that this burn is so small that the G&N system does not actively monitor the burn's Delta-V. Therefore it is an open-loop burn.

Delta-V_c: 18.6 fps (5.7 m/s). This value is entered into the Delta-V display of the EMS (Entry Monitor System) panel. It descends to zero as the engine burns. The EMS will shut down the engine is the G&N system does not. The value given is less than Delta-V_t to take account of the extra thrust from the engine after shut down.

Sextant star: Star 23 (Denebola, in Leo) visible in sextant when shaft and trunnion angles are 201.3° and 16.4° respectively. This is part of an attitude check.

Boresight star: Star 12 (Rigel, in Orion) is used for a second attitude check which is made by sighting through the COAS (Crew Optical Alignment Sight).

COAS Pitch Angle: Up 27.6°.

COAS X Position Angle: Left 0.4°.

Other parameters on the PAD sheet are not applicable to this maneuver.

GDC align stars: Stars to be used for GDC align purposes are the north set (Polaris and Navi). The align angles are roll, 68°; pitch, 97°; yaw, 356°.

The SPS propellant tanks are full, so there is no need to perform an ullage burn to settle their contents.

Apart from the combustion chamber and exhaust nozzle, the SPS engine is really two redundant, highly reliable engines in one. Two sets of plumbing, propellant valves and control circuitry exist (called the A and B control banks) and the engine can be started with either or both. Normally, for long burns, both control banks are used but for short burns like this one, only one (usually the primary or A bank) is needed.]

[As is the normal practice on all these missions, a member of the crew reads back the PAD so that Mission Control can check it has been properly copied down.]

010:02:29 Mattingly: Roger, Apollo 8. That's correct. And I have a TLI plus - 11 PAD for you. [Long pause.]

010:03:02 Borman: Roger. Go ahead. [Long pause.]

010:03:16 Borman: Houston, Apollo 8. Go ahead.

010:03:18 Mattingly: Roger, Apollo 8. Loud and clear now. Are you ready to copy?

010:03:23 Borman: Roger. Ready to copy.

010:03:24 Mattingly: Okay. This is a TLI plus 11, SPS/G&N. This assumes a midcourse correction number 1: 63140; minus 1.63, plus 1.29; 013:56:48.97; minus 0059.9, plus 00000, plus 4701.6; 177, 143, 000; November Alpha, plus 0019.7; 4702.0, 5:51, 4681.8; 12, 128.3, 25.7; 023, up 26.3, left 1.7; plus 11.95, minus 165.00; 1268.3, 35608, 050:47:05; north stars; 068, 097, 356; no ullage. For the fast return P37 Delta-V, 7900 for the Indian Ocean, high speed procedure not required for the MS. This assumes midcourse correction 1. Over.

[The PAD is interpreted as follows:

Purpose: This PAD is another contingency in case of abort for a return to Earth with an ignition time approximately 11 hours after TLI.

Systems: The burn would be made using the large SPS (Service Propulsion System) engine at the rear of the Service Module, under the control of the Guidance and Navigation system. The figures are only valid if the crew have carried out their first midcourse correction.

CSM Weight (Noun 47): 63,140 pounds (28,640 kg).

Pitch and yaw trim (Noun 48): -1.63° and +1.29°.

Time of ignition (Noun 33): 13 hours, 56 minutes, 48.97 seconds. This is about 11 hours after TLI.

Change in velocity (Noun 81), fps (m/s): x, -59.9 (-18.3); y, 0; z, +4,701.6 (+1,433.0).

Spacecraft attitude: Roll, 177°; Pitch, 143°; Yaw, 0°.

H_A, expected apogee of resulting orbit (Noun 44): Not applicable. If this abort burn were to be made, the apogee of the resulting orbit would be over 9999.9 nautical miles, beyond the limit of the computer's display.

H_P, expected perigee of resulting orbit (Noun 44): 19.7 nautical miles (36.5 km). The perigee distance is so low, it intersects the Earth's atmosphere. In other words, the spacecraft will re-enter.

Delta-V_t: 4,702.0 fps (1,433.2 m/s). This is the total change in velocity the spacecraft would experience. (It is a vector sum of the three components given above.)

Burn duration or burn time: 5 minutes, 51 seconds. Unlike with the short burn in the previous PAD, this is a long burn and the G&N system will monitor the achieved Delta-V and shut down the engine at the correct time to achieve the required effect. This is therefore a closed-loop burn.

Delta-V_c: 4,681.8 fps (1,427.0 m/s). The crew enter this Delta-V into their EMS (Entry Monitor System) for backup control of the engine.

Sextant star: Star 12 (Rigel, in Orion) visible in sextant when shaft and trunnion angles are 128.3° and 25.7° respectively. This is part of an attitude check.

Boresight star: Star 23 (Denebola, in Leo) This is a second attitude check which is made by sighting on another celestial object with the COAS.

COAS Pitch Angle: Up 26.3°.

COAS X Position Angle: Left 1.7°.

The next five parameters all relate to re-entry, during which an important milestone is "Entry Interface," defined as being 400,000 feet (121.92 km) altitude. Another important point is when atmospheric drag on the spacecraft imparts a deceleration of 0.05 Gs.

Expected splashdown point (Noun 61): 11.95° north, 165° west; in the mid-Pacific.

Range to go: 1,268.3 nautical miles (2,348.9 km). To set up their EMS (Entry Monitor System) before re-entry, the crew need to know the expected distance the CM would travel after Entry Interface.

Expected velocity at Entry Interface: 35,608 fps (10,853 m/s).

Time of Entry Interface: 50 hours, 4 minutes and 05 seconds GET. This is the predicted time at which the spacecraft would be at 400,000 feet (121.92 km) altitude.

GDC align stars: Stars to be used for GDC align purposes are the north set (Polaris and Navi). The align angles are roll, 68°; pitch, 97°; yaw, 356°.

The SPS propellant tanks are full, so there is no need to perform an ullage burn to settle their contents.

If the crew need to get to Earth faster for any reason, they can hurry things up by adding 790 feet per second (241 m/s) to their forward velocity which will bring them to a landing in the Indian Ocean.]

010:06:23 Mattingly: Roger. [Long pause.]

010:06:40 Borman: Houston, Apollo 8. To the readback. Are you ready?

010:06:43 Mattingly: Go ahead.

010:06:44 Borman: TLI plus 11; SPS/G&N; 63140; minus 1.63, plus 1.29; 13:56:48.97; minus 0059.9, plus 00000, and I believe it's plus 4701.6.

010:07:14 Mattingly: Affirmative. [Pause.]

010:07:20 Borman: 177, 143, 000; N/A, plus 0019.7; 4702.0, 5:51, 4681.8; 12, 128.3, 25.7; 023, up 26.3, left 1.7; plus 11.95, minus 165.00; plus 1262.3, 35608, 050:47:05; the north set; roll, 68; pitch, 97; yaw, 356; no ullage, P37 high speed, 7900 Indian Ocean, and high speed procedures for the MS are not required; assumed MCC 1.

010:08:42 Mattingly: Roger, Apollo 8. Two corrections on the GETI. The hour's 013. Range to go EMS.

010:08:57 Borman: 013.

010:09:00 Mattingly: Roger. Copy that and the range-to-go in the EMS 1268.3. Over.

010:09:11 Borman: 1268.3.

010:09:13 Mattingly: That's correct.

010:09:16 Borman: Houston, this is Apollo 8. Be advised that we doubted that it would be possible to use the stars to get our backup alignment. We haven't been able to see any stars through the scanning telescope yet.

010:09:30 Mattingly: Roger. [Pause.]

010:09:40 Mattingly: Okay. And another comment for you, Apollo 8; like for you to use Verb 37 to select P00 and then wait for your computer activity light to go off prior to unzap of the LM NAV to CSM slots.

[Verb 37 allows the crew to change the program that is running in the computer. Slots in memory set aside to hold the LM state vector are instead used to hold an alternative version of the CSM's state vector. Occasionally, they may wish to make a fresh copy of the values currently in the CSM slots into the LM slots. If they do so, they should use Verb 37 to set the computer to Program 00 first. This may be to ensure that all pertinent activity in the computer has stopped prior to the transfer.]

010:10:00 Mattingly: That's affirm. [Long pause.]

010:11:00 Borman: Houston, this is Apollo 8.

010:11:03 Mattingly: Go ahead.

010:11:05 Borman: Okay. Now we'll go ahead and start back towards the Flight Plan around 8 hours here of P52, right?

010:11:14 Mattingly: That's affirm.

[The first midcourse correction has been delayed so all the steps in the Flight Plan that lead up to it have been delayed also. The first of these is a realignment of the guidance platform using P52 in the computer.]

010:11:43 Mattingly: Okay, Apollo 8. That's good procedure and...

[Long comm break.]

010:16:13 Mattingly: Apollo 8, Houston.

010:16:16 Borman: Go ahead, Houston.

010:16:18 Mattingly: Roger. Will you check your up-telemetry switch to Block, please?

010:16:24 Borman: Thank you. It's in Block.

[Very long comm break.]

[The Up Telemetry switch was placed in Accept twenty minutes ago so Mission Control could send up data pertinent to the upcoming burn. The DSE is placed in the Record mode.]

010:20:01 Lovell (onboard): We haven't done P30 yet.

[The DAP is the Digital AutoPilot. However, its parameters don't get loaded quite yet. Program 30 should be executed first. This sets up all the parameters relating to the burn so that a subsequent program, P40 or P41, can use them to actually execute the burn. It is the first item in the SPS thrusting checklist on page G-43 of the Guidance and Navigation checklist.]

010:20:22 Lovell (onboard): Okay.

[This changes the computer's current program to P30.]

010:20:24 Lovell (onboard): 10:59:58.30.

[This is the time for the ignition of the burn as read up to the crew in the MCC-1 PAD.]

010:20:34 Lovell (onboard): Okay, 136, good; minus three balls 45 is good; plus 00202, good. I like it. Proceed.

[Jim has entered the three velocity components for the burn.]

010:20:51 Lovell (onboard): Okay, 1685 [garble]. Okay, I'll - Okay, that's good.

[Jim is entering the desired apocynthion of their new trajectory, i.e. how far above the Moon's surface they will be as they pass around its far side and get closest to it.]

010:21:12 Borman (onboard): Well, all our stuff is counting up though, isn't it?

[To help them coordinate the final steps leading to the burn, they set the Digital Event Timer so that it will count up to read 1:00:00 at the time of ignition. This requires presetting it and starting it at the right time]

010:22:43 Anders (onboard): [Garble] go to POO.

[The check list calls for them to put the computer in P00, its do-nothing state, prior to maneuvering to the required attitude for the burn.]

010:23:08 Anders (onboard): ISS, On. SCS, operating; test the Caution/Warning lights.

[Bill is now reading from the checklist for P40 at the top of page G-43. The crew are, strictly speaking, completing some of these items out of sequence. This may be related to their intensive training and familiarity with the procedures as gained in many simulations, as distinct from strictly following the letter of the checklist.]

[CMC is the Command Module Computer. SCS is the Stabilization Control System. The two represent separate and redundant ways of controlling the attitude of the spacecraft; the computer working with the IMU, the SCS using separate gyro assemblies.]

010:23:26 Borman (onboard): Delta-V, Set.

[They are putting the EMS through a test to check that it will display changes in velocity properly. A number will be put in the Delta-V display, a test signal will be fed in and the display should decrease to display -20.8 fps with a tolerance of ±20.7 fps.]

010:24:35 Borman (onboard): Standby.

[The EMS checks out well. Frank can now load it with the velocity it is going to read at the start of the burn, Delta-V_C.]

010:25:07 Anders (onboard): Okay. Nonessential bus is going to Main B.

[Non essential items in the spacecraft are powered via a separate electrical distribution bus. This allow all these items to be shut down easily should there be a power shortage. For now, it is being powered from the secondary power bus.]

010:25:34 Borman (onboard): BMAG Mode, three, Rate 2 - 2, 3.

[In addition to the gyros that help hold the guidance platform in position the IMU (Inertial Measurement Unit), there are two further gyro assemblies, each of which contain three Body Mounted Attitude Gyros (BMAGs). Unlike the gimbal mounted gyros of the IMU, these BMAGs are fixed to the spacecraft. However, by their tendency to want to remain in one attitude, they exert a force on their mountings which is a measure of the rate of the spacecraft's rotation. By throwing three switches to Rate 2, Frank is assigning the measurement task for roll, pitch and yaw to the gyros in unit number 2.]

[The Delta-V_CG switch is rarely mentioned in the Apollo literature.

While the SPS engine is thrusting, the SCS (Stabilization and Control System) fires the RCS thrusters to keep the spacecraft aimed appropriately. Were there to be a Lunar Module docked to the apex of the CSM, the centre of gravity of the whole craft would be shifted well away from where it would otherwise be. This switch alters the gain of the SCS to account for this. Obviously, with there being no LM on this mission, the switch stays in the CSM position.]

010:25:43 Borman (onboard): CMC Mode, Free.

[The spacecraft's computer is often called the CMC (Command Module Computer). By placing the CMC Mode switch to Free, the computer plays no part in controlling the attitude of the spacecraft.]

[In this case, none of the sixteen RCS jets are required for ullage. If they were, there are 16 switches on panel 8, which is on Frank's side of the Main Display Console, which allow each thruster to be enabled from either the main or backup power busses.]

010:25:52 Lovell (onboard): Okay, Verb 48, Enter. Okay, that's good, right?

[Verb 48 allows a routine to be accessed to define how the DAP operates. In this case, Jim is going to load the current spacecraft weight and the trim angles for the SPS engine.]

010:26:50 Borman (onboard): Normal, AC/DC.

[This ensures the Rotational Hand Controllers are powered.]

010:27:06 Borman (onboard): Auto.

[Having previously placed the attitude control of the spacecraft to Free while the RCS and the DAP are configured, Frank now puts the computer in charge of keeping them pointing the right way.]

010:27:12 Lovell (onboard): Verb 62, Enter; Verb 49, Enter.

[The first verb requests the computer to display the current attitude error, this being the error between two attitudes, the present attitude, stored as Noun 20, and a new attitude, stored as Noun 22 but yet to be entered. Verb 49 initiates a procedure for the crew to maneuver the spacecraft to a new attitude.]

010:27:20 Lovell (onboard): Verb 25, Enter; and it's 345 - 3, 4, 5...

["Verb 25" seems to be an error, probably in transcription. The computer would be flashing 06 22 at this point, essentially asking the crew to enter the attitude for the burn.]

010:27:54 Borman (onboard): Proceed.

[Going through a set of queries from the computer, presented as numerics on a display and to which the answer is "Proceed", the crew set the spacecraft slowly maneuvering to the required attitude. Note that they don't have to manually steer it; the computer looks after such attitude changes.]

010:28:47 Borman (onboard): Rolling right, and yawing left.

Public Affairs Officer - "At the present time, the mission is proceeding nominally. All the spacecraft systems are functioning very well and we have no problems to speak of at the present time. The crew is very heavily involved at this time and preparing for that mid-course correction, the first use of the Service Propulsion System engine. That is scheduled to occur at 11 hours Ground Elapsed Time or about 33 minutes from now. Now that burn is a planned 2½-second burn - a very short ignition of the 20,500 pound thrust SPS engine. It will give them a velocity change of about 24 or 25 feet per second. At this time Apollo 8 is about 50,000 nautical miles [92,600 km] from Earth and they're traveling at a speed of about 8,500 feet per second or around 5,700 miles per hour [2,600 m/s]. We'll stand by to pick up any conversations that develop with the crew prior to this mid-course correction. At 10 hours, 27 minutes this is Apollo Control."

010:29:24 Mattingly: Apollo 8, Houston.

010:29:27 Borman: Go ahead, Houston. Apollo 8.

010:29:30 Mattingly: Okay. We've got a telescope alignment if you'd like to give it a try. Your sextant star is still good, but if you had problems with that, folks have worked out that if you look through the telescope at 10:35, we have a shaft and trunnion that should point you at the center of the Earth, if you would like to give that one a try.

[Jim has had problems thus far in the mission with trying to identify all but the brightest stars in the scanning telescope, especially if the Sun or Earth are casting light over it. Its name implies that it magnifies, but actually, the scanning telescope has a power of just one and has a wide angle of view making it susceptible to light spill from bright sources. Jim wants to use it to cross check their attitude, the function of the boresight star. Mission Control are suggesting an alternative whereby the telescope is aimed at Earth.]

010:29:52 Borman: Okay.

010:29:55 Mattingly: Okay. At 10:35...

010:29:58 Borman (onboard): [Talking over Mattingly] Write that down.

010:29:59 Lovell (onboard): Okay, here, I got it.

Mattingly (continued): ...the shaft angle 006.2, trunnion 18.9. Over.

010:30:13 Borman (onboard): Did you get that, Jim, there?

010:30:15 Anders: Roger. 10:35: shaft 006.2, trunnion 18.9.

010:30:20 Mattingly: That's affirmative.

010:32:28 Mattingly: Apollo 8, Houston.

010:32:32 Borman: Go ahead.

010:32:34 Mattingly: Okay. We'd like to get a fan - a cryo fan cycle in here before the burn. About 1 minute on each should be fine.

010:32:44 Anders: Roger. I've already given 2 minutes on H₂ 1 and 2 and O₂ 1, and I've just started O₂ 2.

010:32:52 Mattingly: Roger. Thank you.

[Comm break.]

[A stirring of the cryogenic tanks came earlier in their checklist. Bill began stirring them seven minutes ago.]

010:34:26 Anders: Roger. It's only been running here about 15 minutes. [Pause.]

010:34:43 Mattingly: Okay, Apollo 8. That's - that's correct. You're on high bit rate, and we're afraid you may run out before the burn, so we'd like to dump it, and give it back to you with a full load before the burn.

010:35:00 Anders: Roger. And give us a comment on the voice quality.

010:35:04 Mattingly: Wilco.

[Comm break.]

[The DSE recorder includes a voice track which is also dumped to Earth along with all the data on the tape. Flight Controllers can review this track, if they wish, because it sheds light on how the crew function during major events during the mission. The onboard recording will not be resumed until two minutes before the burn.]

[Later in the mission, the crew will use it as a private communication channel to get a message to the controllers without many others knowing about it.]

010:36:51 Mattingly: Go ahead.

010:36:54 Anders: Roger. We plan to stop charging battery B about another 5 minutes. You concur?

[Bill began charging battery B three hours into the mission.]

010:37:07 Anders: Okay. You might just remind us.

010:37:10 Mattingly: Wilco.

[Long comm break.]

010:43:12 Borman: This is 8. Go ahead. [Pause.]

010:43:20 Borman: Go ahead, Houston. You were cut out.

010:43:22 Mattingly: Okay, Apollo 8. All your systems are Go, and we were about to tell you, you can go ahead and terminate the battery charge, and you beat us to the punch.

010:43:35 Borman: I read your mind, and it's showing 37 volts right now.

010:43:40 Mattingly: Okay.

[Very long comm break.]

[The spacecraft has adopted the appropriate orientation in space to carry out the burn. Jim makes doubly sure that this attitude is correct by sighting through two instruments: the COAS and the sextant.]

[Since the crew are using the big SPS engine for this maneuver, they must check the motors and gimbals that allow the SPS engine to swivel, changing the direction it points. Angles to set it to were included in the PAD for this burn. This check of the TVC (Thrust Vector Control) system begins midway down page G-45 of the guidance checklist and should have commenced by now.]

010:54:43 Mattingly: Apollo 8, Houston. If you'll put your high bit rate on, we'll give you a tape recorder back.

010:54:49 Borman: Roger.

[Comm break.]

010:56:50 Borman: Houston, did you give us a tape back? Over.

010:57:06 Mattingly: Affirmative, Apollo 8.

010:57:09 Borman: Apollo 8's Command Reset to get tape motion, we're now in Normal.

010:57:20 Mattingly: Roger.

[Comm break.]

[The DSE is placed in Record mode and the subsequent recording finds the crew only two minutes away from the burn. Bill and Frank are continuing their challenge-and-response methodology as they work through the checklist for the burn. They are at the top of page G-47 in the Guidance and Control checklist.]

010:57:55 Borman (onboard): Main Thrust, Normal.

[There are two large guarded switches on panel 1 to the left of the Main Display Console which, if thrown, permit the SPS engine to fire.

There is one switch for each of the two redundant control banks of the engine, A and B. For this burn, only the A bank will be used. The switch sends power to the engine and the pre-valves in the propellant lines, and it signals to the computer that the engine is ready to fire.]

010:58:17 Borman (onboard): Okay.

[The display on the DSKY will blank 35 seconds before the burn. However, there is another minute before this happens.]

Public Affairs Officer - "1 minute, 30 seconds from ignition of the SPS engine for that 2.4-second burn. That maneuver will be primarily to control the altitude of the spacecraft as it goes around the back side of the Moon at perigee. Targeting for there is 60 nautical miles [111 km]."

[Frank is querying Bill about when he will switch the EMS to Auto mode. Bill points out that, by the checklist, this doesn't occur until 30 seconds to the burn has passed.]

010:58:42 Borman (onboard): We hear you.

010:58:42 Mattingly: Apollo 8, stand by for a mark at 1 minute.

010:58:48 Borman: Roger. Apollo 8 standing by.

010:58:49 Mattingly: ...Ten seconds [to the one minute mark].

010:58:50 Anders (onboard): Yes. Alright, I'll...

010:58:54 Mattingly: Five seconds.

010:58:57 Mattingly: 2, 1...

010:58:59 Mattingly: Mark.

010:59:00 Mattingly: One minute.

010:59:01 Borman: Roger.

[Long comm break.]

010:59:25 Anders (onboard): EMS MODE, Auto; average g is On.

[The G & N system is measuring acceleration as it begins monitoring the burn it is about to make.]

[The PIPAs are Pulse Integrating Pendulous Accelerometers. There are three of them within the spacecraft's IMU which measure acceleration along the spacecraft's cardinal axes. Part of their calibration includes careful monitoring of their output when no acceleration is applied, i.e. when no engines are firing. This bias signal is the zero point for the subsequent measurements of the spacecraft's acceleration.]

[The operating principles of Pulse Integrating Pendulous Accelerometer is actually very simple. A small mass (the pendulum) is aligned along a specific velocity axis, and an accelerating force can be measured through the torque it exerts on the pendulum. The measured acceleration is averaged over a short time period (several milliseconds) and converted to a value which sent as a string of pulses (think of a serial string of bits). These pulses are sent to the computer, where they are accumulated (integrated) over time to give the total acceleration.]

010:59:31 Borman (onboard): No ullage, yes.

[The four huge propellant tanks are full. There are no appreciable gas voids that could be ingested into the engine so there is no need to have a small RCS firing before the main burn to settle the propellants to the bottom of the tanks. Unknown to the crew and ground controllers, there is, however, a helium gas bubble trapped in the piping leading to the engine. This will cause a momentary drop in thrust when it is ingested by the engine.]

010:59:47 Anders (onboard): Flight Recorder.

[As well as the DSE, there is an additional recorder called the Flight Qualification Recorder. This unit was only included in early versions of the flight-capable Command Modules. It records a limited set of telemetry as part of the effort to qualify the spacecraft and, unlike the DSE which records digital signals, the Flight Recorder is analogue. It is intended only for post-mission analysis, is not replayed to the ground and is only placed in record for ascent, entry and firings of the SPS engine.]

010:59:50 Borman (onboard): 10, 9.

010:59:55 Lovell (onboard): Enabled.

[With five seconds to go, the computer flashes 99 to the crew on the DSKY's Verb display. The computer is asking the crew to enable it to fire the engine and it is answered by the Proceed button being pressed. The engine ignites a half second before 11 hours GET, just over a second late and burns for 2.4 seconds.]

011:00:13 Lovell (onboard): It's holding; let's go, let's go through the checklist.

[The crew pick up the checklist at the bottom of page G-48. Jim's comment that "it's holding" may be referring to the velocity display on the EMS showing no further change in their forward speed.]

011:00:30 Borman (onboard): They're Closed.

[This is at the top of page G-49.]

[These are the motors that drive the gimbal-mounted SPS engine, allowing it to change the direction of its thrust. They are part of the TVC (Thrust Vector Control) system and must be turned off one at a time.]

011:00:53 Anders (onboard): Okay, null residuals.

[When the PAD was read to the crew, it included the velocity change they should achieve with the SPS burn. This was resolved into the three axes of the IMU's orientation, and was also given as a single velocity change along the spacecraft's longitudinal axis. However, the engine has underperformed and they haven't quite achieved this change. There are residual velocities still to be gained in two of the three axes and the crew have them displayed on the DSKY. They will reduce them to zero with additional firings of the RCS thrusters, thereby gaining all the velocity change the wanted.]

011:01:19 Borman (onboard): Yes, I know it.

[Jim is probably referring to the velocity change that they have still to gain (4.4 fps [1.3 m/s]). Note that this is not with respect to the IMU orientation. It is with respect to the spacecraft's longitudinal axis.]

011:01:52 Borman (onboard): Standby.

[They are no longer using the EMS to measure their velocity.]

011:01:54 Borman (onboard): Rate 2.

[During the checkout of the TVC system around 010:54, the BMAGs had been placed in their Att 1/Rate 2 position whereby one of the gyro assemblies was used to give attitude information while the other was used to generate rate of rotation information. They are now reset to a position where the second gyro assembly is being used to give rotational rate information to the FDAIs (Flight Director Attitude Indicators) for roll, pitch and yaw.]

011:01:56 Borman (onboard): Deadband, Max.

[It is often important that the spacecraft be held in a specific attitude. However, to react to the slightest error in attitude would be wasteful of fuel as there are constant perturbations that keep taking the spacecraft out of perfect attitude. Therefore, a band of attitude error around the ideal is defined within which there will be no active correction. This is the deadband and is set to either ±5.0° or ±0.5°. The Deadband switch on the Main Display Console only has an effect if the spacecraft attitude is under SCS control rather than being controlled by the CMC and its associated systems.]

011:02:43 Borman: Houston, Apollo 8.

011:02:45 Mattingly: Go ahead.

011:02:48 Borman: Roger. The burn time was on time - about 2 seconds; we have residual 4.4 [in the] X [axis]. We burned it out to 0.2. Attitudes are nominal. The Delta-V_C, before the residuals were taken out, was a minus 2.4. I have transferred the state vector to the LM's slot in Verb 66.

011:03:14 Mattingly: Roger. Copy 4.4 for X and 2.4 on C. And negative residual on Y prior to the trim. Is that affirm?

011:03:24 Borman: That's affirmative, and we took out the 4.4 residual down to 0.2.

011:03:29 Mattingly: Roger. [Long pause.]

[As mentioned previously, the engine has underperformed and rather than achieving a 24.8 fps change, it has only brought about 20.4 fps change. There are two reasons for this; one of a long term nature, the other not. During Apollo 8, the way SPS burns are calculated is different when the burn is less than 6 seconds long. During long burns, the computer measures the achieved velocity change every two seconds. Based on this, it then works out how much longer the engine needs to burn to achieve the required overall Delta-V. Shorter burns don't benefit from this "closed-loop" control. Instead, a burn duration is calculated based on the expected engine performance. If the actual engine performance is different, the final velocity error will be small enough that the RCS can be used to take it out.]

[According to the Post-Mission Report, the engine exhibited an overall low thrust due to the pressure with which the propellants were being injected into the engine being lower than expected. This pressure comes from helium that fills the ullage space in the propellant tanks. Additionally, there was a bubble of helium gas trapped in the oxidiser lines which was ingested into the combustion chamber very soon after the engine ignited. The bubble had been there since the tanks were filled prior to launch. The procedure for bleeding the lines had failed to remove this bubble resulting in a large dip in thrust lasting half a second, a considerable length of time in a burn lasting 2.4 seconds.]

011:04:20 Mattingly: Standby. [Long pause.]