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Apollo 10

Day 4 part 12: Lunar encounter

Corrected Transcript and Commentary Copyright © 2010 by David Woods, Robin Wheeler and Ian Roberts. All rights reserved.
Last updated: 2017-02-10
[The Apollo 10 combined CSM/LM spacecraft has nearly completed its journey out to the Moon. The precision of the TLI maneuver was such that only one small midcourse correction was required to place the spacecraft on a trajectory to the desired point in space, from which to insert itself into lunar orbit using the Lunar Orbit Insertion (LOI) burn. This burn would be retrograde to slow the spacecraft velocity so that it is captured by the Moon's gravity field and placed into the desired initial lunar orbit.]

[This was to be only the second time this maneuver had been made. Lessons learnt from the Apollo 8 mission would be factored into the Apollo 10 LOI maneuver so that the resulting orbit matched closely that which Apollo 11 would use for the first lunar landing attempt.]

[The crew follow a very detailed checklist to prepare for the LOI burn after they receive their final guidance updates from MCC-H, realigning the guidance platform and updating the CMC with the precise LOI PAD details. The SPS engine in the Service Module is checked out and prepared for this, its longest burn.]

[The LOI maneuver has to take place above the far side of the Moon, at the pericynthion of the translunar trajectory the spacecraft has been following since the midcourse correction. As this maneuver takes place behind the Moon as seen from Earth, communications will be lost with the spacecraft whilst the burn is made and the crew must monitor the spacecraft's trajectory, the performance of the SPS engine, and the progress of the burn. They have to be ready to take manual control of the burn should an out-of-nominal situation occur. There are several abort modes available to the crew, depending on the cause of the problem and the time at which it occurred.]

Diagram showing the relative trajectories of the Apollo 10 spacecraft and S-IVB third stage as they approach the Moon. Where two times are shown, they are for the spacecraft on the first and second lunar orbits. 11 minutes must be added to these times to allow for the slightly delayed lunar arrival.]

Flight Plan - Page 3-38

072:02:27 Duke: Hello. Apollo 10, Houston. Over.

072:02:34 Cernan: Go ahead, Houston. This is 10. Over.

072:02:38 Duke: Roger, 10. We have a problem with the Goldstone. We won't acquire the 210-foot [64-metre] dish, until 72:49. That means that we'll have to get the color down through the 85-foot [26-metre] dish at Goldstone at 72:14. Now, we’re not sure just exactly how good the color quality will be through the 85, so we can work it your choice on the thing. We can go, as scheduled, at 72:20 and see what the quality of the color is, and if it's bad and it won't impact your time line, we suggest that you then delay until 72:50 when we pick up the 210 and try another show. Also, that would give us - At this time you are in the lunar umbra and your friendly geologist [scientist-astronaut Harrison Jack Schmitt], here, says that there should be a spectacular shot looking right through the Moon into the solar corona. Over.

Goldstone 64-metre dish

[The 210-foot communications dish at Goldstone, California.]

072:04:21 Young: Houston, this is 10. We're kicking around shooting the TV at the solar corona. I don't know. Do you think the thing would handle it? Seems like it would damage it, from the light standpoint.

072:04:33 Duke: Stand by. Everybody is shaking their heads back here - the experts. As long as the Sun is completely down, or completely set, it should be all right. We'll be looking at just a shafting from around the Moon. We think it'll be all right; you could probably take a peek out your window and if it looks all right to you, then you could turn the camera over that way.

072:05:17 Young: We don't see the Sun. We don't see it.

072:05:31 Stafford: [Garble]. [Long pause.]

PAO: This is Apollo Control at 72 hours, 6 minutes. We are standing by waiting for some word on what will be attempted for this next TV transmission at the regularly scheduled time, as you heard Charlie Duke pass up to the crew. Goldstone will not be able to acquire with the 210-foot [64-metre] antenna. The 85-foot [26-metre] antenna will be available but we're doubt the quality of color TV we can receive through this antenna. The 210 [means 85] dish will acquire at 72 hours and 9 minutes. The regularly scheduled TV pass is at 72 hours, 20 minutes. We are now at 72 hours, 7 minutes. We may try to come up at the regular time, feed through the 85-foot [26-metre] dish, see what the quality is; if it is bad, hold off until about 72:50. We'll continue to stand by for a resolution of this.

072:06:08 Unidentified Crew member: [Garble].

[Comm break.]
072:07:28 Unidentified Crew member: [Garble] six.

072:07:40 Duke: Roger, 10. We're just barely reading you, Tom. We are looking at your display: 29 - for perilune of 2906. You are very scratchy, 10; at least Tom is. Almost unreadable. [Long pause.]

[Charlie Duke is referring to the pericynthion altitude currently being displayed in MCC-H. The figure being displayed, 290.6 nautical miles, is substantially higher than the 60 nautical miles they have been targeted to.]
072:08:31 Young: Houston, this is 10. Radio check. Over.

072:08:36 Duke: Roger. You are five-by, John. Over.

072:08:42 Young: Roger.

072:08:47 Stafford: Roger, Charlie. How do you read me now? Over.

072:08:49 Duke: Roger, Tom. You are five-by. Over.

072:08:55 Stafford: Okay. Real fine.

[Long comm break.]
072:12:03 Unidentified Crew member: [Garble].

072:12:08 Duke: Roger, 10. Go ahead. Over.

072:12:15 Unidentified Crew member: [Garble].

072:12:21 Duke: 10, you - You'll have to say again, Tom. You're barely readable. Over.

072:12:31 Stafford: [Garble] our distance to the Moon and our present velocity.

072:12:41 Duke: Roger. Understand. You want distance to the Moon and distance to the Earth. Over.

072:12:52 Stafford: That's affirmative. Distance from the Earth, distance to the Moon and our present velocity.

072:13:01 Duke: Roger, 10. Tom, you're five-by now. You are breaking up; a couple of your transmissions have been barely readable. This last one was five-by.

072:13:11 Stafford: Okay. [Long pause.]

072:14:11 Duke: Hello, 10. Houston. Your present distance from the Earth is 208,950 [nautical] miles [386,975 km]. Distance from the Moon, 9,813 [nautical miles, 18.174 km], with a velocity relative to the Earth of 3,013 feet per second [919 m/s]. Over.

072:14:37 Stafford: Roger, Houston. I have that copied down. Thanks a lot.

072:14:42 Duke: Roger. [Pause.]

072:14:51 Duke: Hello, 10. Houston. We're standing by for your decision on the TV. Over. [Long pause.]

072:15:47 Stafford: Okay. We'll give you an external shot at 00:20 minutes.

072:16:04 Duke: Roger. Standing by for the TV.

[Comm break.]
072:18:29 Cernan: Hello, Houston. The tube is on right now.

072:18:32 Duke: Roger, 10. Stand by. We don't have a picture yet. Over. [Long pause.]

PAO: This is Apollo Control at 72 hours, 19 minutes. We are going to attempt to get a TV feed through the 85-foot [26-metre] dish at Goldstone. The crew indicates that they have the camera turned on. We're standing by now.

072:19:23 Duke: We’re in the process of handing over to Goldstone. Goldstone as yet has not received your signal and we'll let you know. Over.

072:19:30 Stafford: Okay. We’ve got a beautiful picture on our monitor this morning.

072:19:34 Duke: Good show, 10. Over.

[Comm break.]
PAO: A few minutes ago at 72 hours, 13 minutes, Tom Stafford asked for his distance from the Earth to the Moon and the velocities. These are the figures we passed up to him at 72 hours, 13 minutes. Apollo 10 is 208,950 nautical miles [386,973 km] from the Earth. Velocity; 3,013 feet per second [918 m/s] relative to the Earth. Distance from the Moon; 9,813 nautical miles [18,736 km]. Velocity relative to the Moon; 4,234 feet per second [1,291 m/s]. We're continuing to stand by to see whether we'll be successful in getting this TV feed through the 85-foot [26-metre] dish.

072:20:56 Cernan: Give us a hack when you're getting a picture, would you please?

072:21:00 Duke: Roger, 10. We'll do that. Stand by. I'll give you some word on the Goldstone acquisition.

072:21:13 Stafford: Okay. If they don't have it before too long, we'll go ahead and terminate it.

072:21:19 Duke: Roger, 10. If you'll stand by for 2 seconds, we'll give you an estimate of acquisition time. We're supposed to have it at 72:14. So far, they haven't got a signal through the 85. [Long pause.]

072:22:19 Stafford: Houston, while you're waiting for Goldstone, we'll just keep locked-on here. We'd still like to have you check with GUIDO why we have a 290 - a 290.6 perilune, there, on our Verb 82.

[Verb 82 is used to request display of orbit parameters as part of CMC routine R30. This is used to supplement the parameters uplinked from the ground in case there is a loss of communications.]
072:22:34 Duke: Roger. Stand by, 10. [Long pause.]

072:23:11 Duke: Hello, 10. Houston. The big pericynthion number is due to the conic integration in the Verb 82. At these distances, the GUIDO's are not disturbed. They say that's a normal reaction to that integration, There is a way you can get a better number. If you'd like us to pass it up to you, we'll give it to you. Over.

072:23:37 Cernan: We can take P21 to about the middle of the LOI burn. That ought to tell us.

[Program 21 is used to provide the crew details of the spacecraft's ground track. As part of this program, keying in Verb 22 Enter, the crew can enter a time into register 2, and the CMC will display the parameters as latitude, longitude and altitude above the landing site radius (the height of ALS-2, the eventual Apollo 11 landing site above the centre of the Moon) for the time requested. MCC-H will suggest that they request this information for a GET of 076:00:14 which will provide a more accurate figure for the altitude of the spacecraft's pericynthion. The mathematics used in R30 use a mathematical simplification that breaks down near the Moon.]
072:23:45 Duke: That’s the way we were going to suggest, 10. Over.

072:23:52 Cernan: Okay.

072:23:54 Stafford: Okay. We figured it was strictly due to the conic, but we just wanted to give it a recheck.

072:23:56 Duke: Roger. [Pause.]

072:24:06 Duke: Hello, 10. Houston. We suggest your GET for the P21, if you’re going to run it, is 76:00:14. Over.

072:24:23 Cernan: Roger. [Long pause.]

072:24:37 Stafford: Houston, Apollo 10. Do we have anything through Madrid at this time? The Goldstone isn't locked-on. Over.

072:24:48 Duke: 10, Houston. We have a Madrid acquisition and they are getting a picture recorded on tape. Goldstone lockup is estimated in another 10 minutes. So, it's dealer's choice on whether to terminate or not.

072:25:13 Stafford: Okay. We will knock it off now. Let us know when you have acquisition. We will give it to them for just a short bit in about 10 minutes. Tell us when. We don’t want to just keep holding the camera here. We have a few other things to do. We will give it to them in 10 minutes for a short while. Over.

072:25:29 Duke: Roger, 10. We suggest you hold off until we get acquisition, and we will give you the word on acquisition at Goldstone. Over.

072:25:36 Stafford: All right. [Long pause.]

PAO: This is Apollo Control at 72 hours, 25 minutes. As you heard, we will wait 10 minutes for Goldstone acquisition and the crew will try for a short TV transmission at that time.

072:26:03 Stafford: Houston, Apollo 10. If you can read our DSKY, we now show 61.8-mile [114.5 km] perilune. It looks pretty good.

072:26:06 Duke: Roger. We copy.

072:26:08 Unidentified Crew member: Just like you guys said.

[Long comm break.]
PAO: This is Apollo Control at 72 hours, 32 minutes. Goldstone has acquired Apollo 10. We'll stand by until we have a good strong signal and then we'll pass that word up to the crew for another attempt at television.

PAO: Apollo 10's distance from the Moon is 9,028 nautical miles [16,720 km]. its velocity in reference to the Moon; 4,283 feet per second [1,306 m/s].

072:35:08 Duke: Hello, Apollo 10. Houston. Goldstone has a good acquisition. We're Go for TV. Over.

072:35:21 Stafford: Okay, Charlie. We'll get you going right now.

072:35:24 Duke: Roger.

[Comm break.]
072:36:28 Stafford: Hello, Houston. Apollo 10. Our monitor shows a good picture of the Earth. How are you doing?

072:36:33 Duke: 10, we haven't got our signal yet. Stand by. [Long pause.]

PAO: Picture coming up now.

[MP3 audio file.]
072:37:35 Duke: Okay. Apollo 10, Houston. We're getting it in black and white now. Stand by for the color. [Long pause.]

072:37:53 Duke: We've got the color now, Apollo 10. We have the Earth, and the center of the section. It seems to have a bluish tinge to the background. We see a very bright blue - a pale blue I should say, in the center of the Earth right near the terminator. Could you describe that for us? Over.

072:38:15 Stafford: Right. You can see the South Atlantic Ocean there and the orange spot to the right is the North African continent. You can see basically the Sahara Desert and, above that, the Mediterranean Sea. The rest of the world is pretty much encased in clouds. The solid cloud cover that's covered the North Pole, and most of Europe, is still with us today. At this time, as we look at the Earth, we are 210,000 miles [389,000 km] away. We've only got about 9,000 miles [16,700 km] to go to the Moon and we're traveling approximately 2,500 miles an hour [4,600 kph] relative to the Earth. Also, in about 15 minutes we will enter the shadow of the Moon and make our major burn to enter lunar orbit in approximately 3 hours. Now, at this distance, the Earth looks slightly smaller than a tennis ball to us and a little bit larger than a golf ball. And I hope it shows up the same way on your screen.

[In truth, such comparisons are meaningless unless a distance is given. For example, a tennis ball held at arm's length or something similar.]
072:39:18 Duke: 10, it's a...

072:39:19 Stafford: ...And again, South Africa - Go ahead, Charlie.

072:39:27 Duke: Roger. I was just going to add that we can see the northern part of Africa. We had a bluish tint to it at first but now it's coming in to a sort of orangish brown and we can see the South Atlantic and the cloud covers very well. The colors are very good. Over.

072:39:47 Stafford: Roger. Again, the Sahara Desert, the Atlas Mountains, Morocco, Libya we can see from here. It is an orange brownish orange. The night time - the terminator has cut across the Suez Canal and most of Egypt and is now covering most of South Africa. I can see Spain. It is a greenish brown and is completely contrasted with respect to North Africa. However, you may have difficulty seeing it on your set due to resolution at this distance. Again, you can see Brazil, but it is covered mostly with clouds at this time.

072:40:30 Duke: Roger 10. We haven't - We can see...

072:40:35 Stafford: ...At this time Apollo 10...

072:40:37 Duke: ...Go ahead. Go ahead, 10.

072:40:38 Stafford: Roger. This - Roger. At this time Apollo 10 is going through the preparation for the Lunar Orbit Insertion burn, and the next - After we lose contact with the Earth, the next time that we come around, we will – To have contact with the Earth, we'll be at approximately a 60- by 170-mile [111- by 315-km] orbit around the Moon. Right now, we cannot see the Moon, even though it is rapidly accelerating us towards itself by its mass. Over.

072:41:09 Duke: Roger, Tom. We copied. A very good description. We have difficulty seeing any landmass in our picture except for North Africa, and we can see the terminator cutting across Africa. Europe - The landmasses of Europe, are - just sort of fade into a bluish color. It looks like an ocean to us. Over.

072:41:28 Stafford: Right. Really, the only major landmass we can see is exactly what you can see on your set there. And that is the North African continent. Most of Europe is covered either by high clouds or some scattered low clouds and it's very difficult for us to see it, too. We'll give you a quick shot on the interior now, and then we'll terminate this pass. We’ll go inside now.

072:41:57 Duke: Roger. Very good. Thank you very much for the view. We'll be standing by for the inside.

072:42:37 Duke: Hello, Apollo 10. Houston. You are coming in on the black and white monitor now. [Long pause.]

[MP3 audio file.]
072:43:12 Duke: 10, we have the color now. The resolution on the 85 is, I think, better than most expected here. The Sun is pretty bright in the background, coming in through the - I guess that's the hatch window. No; side window, I guess it is. The patch is visible but it's pretty dark, due to the background being so bright. [Long pause.]

072:44:22 Duke: 10, do you read? Over.

072:44:30 Stafford: Go ahead, Charlie.

072:44:32 Duke: Roger. Thought we had lost voice there for a moment. You're coming in five-by, now. We've got your arm patch now. That's very dim at this setting. We had Gene's smiling face there for a minute, along with your patch. The flag is coming in a little bit better now. However, it's still pretty dark due, to the bright background. That's a lot better, there, 10. Over. [Long pause.]

072:45:12 Duke: There. We have a good view now. Now we can see Gene again. [Long pause.]

072:45:35 Duke: We see you waving, Gene. Barbara is in the viewing room. She says "Hi."

072:45:53 Young: A little difficult to get the proper lighting up here, Charlie. Spots flood it out, and we've got to deflect the light.

072:46:05 Duke: Roger. We see you trying hard on the thing. It looks like the ALC [Automatic Light Compensation] is averaging out, and the background looks real good - the spacecraft, back along the hatch. Tom's hand covering his window is real clear; his face is dark, though. Over.

072:46:27 Young: That's those whiskers, there, Charlie.

072:46:30 Duke: I see. Thank you very much, John. That wasn't quite...

072:46:41 Stafford: That's known as a 72-hour shadow, Charlie.

072:46:45 Duke: Yes, sir. [Long pause.]

072:46:59 Duke: Apollo 10, Houston. We now have the 210 at Goldstone. The granularity and the resolution is a heck of a lot better here. You're coming in real great. Over.

072:47:14 Stafford: Okay.

072:47:18 Cernan: There's our overhead hatch window there. [Pause.]

072:47:28 Duke: 10, Houston. We see some specks on your hatch window. Could you comment on those? [Pause.]

072:47:40 Stafford: Yes. They come from the dumps that we're making overboard as we progress along. I don't think any of it is due to the thruster firing, Charlie.

072:47:50 Duke: Roger.

[MP3 audio file.]
072:47:53 Cernan: Houston, the hatch window is phenomenally clear. There is what appear to be a few dump particles on the outside, maybe a couple of smear prints on the inside. The right-hand window has got a little bit of a smear on the outside; not necessarily particles, but just a general smear. The left-side window has got some definite particles lashed across it.

072:48:27 Young: We're not very good at this camera work, but we will probably improve with practice.

072:48:35 Stafford: We will show you the navigator down in the LEB.

072:48:40 Duke: Roger, 10. We have no complaints at all. That's a pretty good show.

072:48:52 Stafford: He's the star of the cast because he gets all the good light down there.

072:48:58 Duke: Roger. There's old John's friendly face.

072:49:00 Duke: (Laughter.) [Pause.]

072:49:12 Cernan: John's pointing right now at the sextant and the telescope, which are our navigation means to get home. And, hopefully, to do part of the rendezvous.

072:49:30 Cernan: Yes. This is the best-working part of the whole machine. It's really working beautifully, now.

072:49:34 Duke: Got a good operator. [Pause.]

072:49:44 Duke: 10, Houston. Show us the piece of tape that you have around the eyepiece.

072:50:01 Cernan: One on the bottom of the sextant and on the righthand side of the telescope.

072:50:06 Duke: Roger. Thank, you much, 10. We see it. [Long pause.]

072:50:19 Cernan: You know, once you lose that thing in here and you have to look for it for about 20 minutes, you find a way not to lose it again.

072:50:22 Young: Well, it wasn't quite 20 minutes but it sure was a scramble going for it, I'll tell you that.

[Young had previously complained about how easy it was for the eyepieces on the sextant and telescope to come off and float away to some unknown corner of the CM. He has now taped both eyepieces in place for the remainder of the mission.]
072:50:28 Duke: Roger. We copy. We have you entering the lunar penumbra at this time. Do you notice the Sun setting at all? Over.

072:50:38 Young: Can't see the Sun right now, Charlie.

072:50:41 Duke: Roger.

072:50:45 Young: We're not in the right attitude to see it.

072:50:54 Stafford: In this attitude, to look at the Earth and everything, we can't get a picture of the Sun that we can see. If there is any solar corona, we will give it a quick shot.

072:51:03 Duke: Roger. Jack is estimating you will have about 30 seconds only. Over.

072:51:14 Cernan: Okay, Charlie. It appears that the Sun's reflection on Snoopy, here, is getting a little bit dimmer. So we very well could be where you [think] we are. I hope we are.

072:51:28 Duke: Your friendly FIDO's will bet on it.

072:51:30 Stafford: [Garble] some navigating here.

072:51:39 Young: Yes. I guess we are too, aren't we?

072:51:42 Duke: Roger. [Pause.]

072:51:50 Cernan: I never doubted them, anyway. I just - Like I said yesterday, I'll wait until I see that 60 nautical miles [111 km].

072:52:01 Duke: 10, Houston. Does it look any different upside-down there?

072:52:08 Young: The stars are 180 out of the position they were before.

072:52:10 Cernan: That's one thing about this environment. If you don't like it, just turn it upside-down.

072:52:20 Duke: Roger, 10.

072:52:21 Stafford: Okay, Charlie. We will terminate this pass with one quick look outside to see how the 210-foot dish looks at the Earth from outside. Okay?

072:52:30 Duke: Roger, 10. We are standing by. Over. [Long pause.]

[MP3 audio file.]
072:53:17 Cernan: Charlie? It's definitely getting a little darker outside.

072:53:22 Duke: Roger, 10. That's good news. Over.

072:53:32 Stafford: Looks like we're right on trajectory, then. Okay. Here's another look at the Earth through the 210-foot dish at Goldstone, and I hope the colors are coming through a little better. Again, the west coast of North Africa is still a bright orange, and the central part of North Africa is starting to turn purple as night-time approaches over the western part of Libya and the eastern part of Tunisia. Again, it's awful hard to see Spain because Spain is a greenish brown this morning. You have the Mediterranean and the Atlantic covered with some clouds, so it's awful hard to see any part of Spain. But again, the Earth to us this morning looks a little bit smaller than a tennis ball as we're 210,000 miles [389,000 km] from the Earth and now less than 9,000 miles [16,700 km] to go to the Moon. This is Apollo 10, signing off. We'll see you later today.

072:54:25 Duke: Thank you much for a good show, 10. Appreciate it. The 210-foot dish is giving us a very good resolution and the colors are a lot sharper. Over. [Pause.]

072:54:45 Cernan: Okay, Charlie. We are definitely in darkness, right at this moment. It just went pitch dark outside.

072:54:52 Duke: Roger...

072:54:53 Cernan: ...Lost all the Sun.

072:54:54 Duke: Roger. We Copy, 10.

072:54:56 Cernan: Boy, that - That's really something, after having the Sun out of one window all the time. We are in total darkness. [Long pause.]

072:55:23 Cernan: That total darkness occurred about 72:55:00.

072:55:35 Duke: Roger, 10. We were predicting about 72:53. Over. That's pretty close, we think. Over.

072:55:45 Unidentified Crew member: Charlie, I can just see a little bit of reflected sunlight now out on the left thrusters. I believe it's probably from the Earth over on the left side.

072:55:55 Duke: Roger, 10. We think it might be Earthshine. We have an update to your LOI-1 burn card. Over.

072:56:06 Unidentified Crew member: Stand by a second.

072:56:08 Duke: Roger. No hurry on this.

[Long comm break.]
PAO: That was Gene Cernan describing Apollo 10's entry into the lunar umbra, the night-time of the Moon. The early part of that TV transmission was through the 85-foot antenna. We then acquired the 210-foot antenna and had a better picture. And Mrs. Gene Cernan watched this television show from the viewing room here in the Control Center.

PAO: At 72 hours, 57 minutes; Apollo 10 is 7,987 nautical miles [14,792 km] from the Moon. its velocity; 4,360 feet per second [1,330 m/s]. That's with a lunar reference.

073:00:37 Cernan: Hello. Houston. Houston, this is 10. How do you read.

073:00:40 Duke: Reading you five-by 10. Go ahead. Over.

073:00:58 Duke: Hello, 10. Houston. We just had a handover to Goldstone. Do you read now? Over.

073:01:04 Cernan: Oh, yes. I thought that was us: We're back on High Gain and Narrow Beam, Charlie.

[The HGA beam width is set by the switch on the lower right side of panel 2. This switch has three settings Wide, Med, Narrow. At the current distance from Earth, high-bit-rate communications dictate that they be in Narrow beam width, especially whilst transmitting color TV pictures.]

HGA Bm Wdth P2

HGA Beam Width switch on panel 2.

Click on above image for full panel diagram.

073:01:13 Duke: Roger. 10. Network has just advised that we won't hand over until 73:05. Over.

073:01:23 Cernan: You will not hand over until 73:05. Okay. And what is that update you have for us?

073:01:34 Duke: Roger. It's two of them. One for your LOI burn card. We have some updates to your angles. And we have a map update, rev number 1. Over.

073:01:57 Cernan: Okay. Give me the rev 1 first, Charlie.

073:02:00 Duke: Roger. LOS is 075:48:25, 075:52:52, 076:22:58. Over.

073:02:25 Cernan: Okay. I’ve got map update, rev 1: 075:48:25, 075:52:52, and 076:22:58.

[These times are for the upcoming Loss Of Signal as the combined spacecraft goes behind the Moon, the time as they pass over 150° West and the acquisition of signal time as they re-emerge following a successful LOI burn.]
073:02:35 Duke: Roger. That was a good readback. Over.

073:02:42 Cernan: Okay. And go ahead with your update on the preliminary LOI.

073:02:49 Duke: Roger. It's on your burn card that you have. It's an update to the roll, pitch, and yaw angles. Roll is now 179 degrees, pitch 68 - that's 068, yaw is 011. Over.

073:03:11 Stafford: Okay. Charlie. That must be for the abort card, right?

073:03:12 Duke: That's affirmative, 10. Over. [Pause.]

073:03:25 Stafford: Roger. Roger.

PAO: This is Apollo Control. Those times that were passed up on the lunar revolution number 1 map update, the first time was the Loss Of Signal time. That's 75 hours, 48 minutes, 25 seconds. The second time is, which Apollo 10 will pass 150 degrees west, was 75:52:52. And the third time was the Acquisition Of Signal time, 76:22:58. We're 2 hours, 49 minutes, 46 seconds away from the Lunar Orbit Insertion burn according to the preliminary maneuver PAD passed up to the crew a short time ago. This time will be updated again prior to that burn. We expect to update the LOI PAD about 74 hours and 10 minutes, and that ignition time may change a little bit.

073:03:46 Cernan: Okay, Charlie. I got roll 179, pitch is 068, and yaw is 011 on the LOI 15-minute abort card.

073:03:56 Duke: That's affirmative, 10. Over.

073:04:01 Cernan: Okay.

[Very long comm break.]
PAO: This is Apollo Control at 73 hours, 26 minutes. Apollo 10 is 6,863 nautical miles [12,710 km] from the Moon. Velocity; 4,464 feet per second [1,361 m/s]. We are in conversation with Apollo 10 now.

073:16:54 Cernan: The LM is bright as day, courtesy Earthshine.

073:16:56 McCandless: Roger. Understand you are getting a lot of Earthshine up there, 10. Over.

073:17:01 Cernan: Roger.

[Long comm break.]
073:20:06 McCandless: Apollo 10, this is Houston. It looks like you're drifting into the limit on the High Gain Antenna. You will be handling the Omnis on board. Looks like you are coming up on Omni Delta for max signal strength. Over.

073:20:24 Cernan: Okay, Bruce. Thank you.

073:20:32 McCandless: Roger. Out.

073:20:40 Stafford: Houston, Apollo 10. As you can see, we've made just a couple of pulses, and we're slowly drifting over to our LOI-1 attitude.

073:20:52 McCandless: This is Houston. Roger. Out.

[Long comm break.]
073:25:14 Cernan: Hello, Houston. This is 10.

073:25:17 McCandless: Go ahead - Go ahead, 10. Over.

073:25:22 Cernan: Okay. Reservicing has started, and I'm at the part where I've got the waterflow on. I'll keep it on for 2 minutes.

[Cernan is reservicing the water/glycol evaporator which had dried out during the first Earth orbit. The function of the evaporator is to provide additional cooling capability for those periods of high heat load when many systems are on and functioning. It works by evaporating excess water from the fuel cells which then cools the water/glycol coolant that runs through plates on the spacecraft's electronics chassis.]
073:25:32 McCandless: Roger. We copy.
[Comm break.]
073:27:58 Duke: Hello, 10. Houston. We show 2 minutes on the water. It looks like you got some water into the evaporator. We suggest you turn it off. Over.

073:28:14 Cernan: [Garble]. Understand you don't want me to activate it at this time? I just went to Auto on the steam pressure and the waterflow.

[Switching the Water Glycol Evaporator Steam Pressure switch to Auto removes AC power from the adjacent Incr/Decr switch, applies AC power to steam pressure/wetness control unit. It also closes the circuit from control section to steam pressure control valve to automatically regulate steam pressure in the evaporator.]

[Placing the H2O Flow switch in the Auto position applies AC power to steam pressure/wetness control unit. It also closes the circuit from control unit to the water control valve for automatically regulating water inflow to water-glycol evaporator.]

Evap ctrl P2

Water Glycol Evaporator Steam Pressure & H2O Flow switches on panel 2.

Click on above image for full panel diagram.

073:28:20 Duke: Roger. That’s the correct procedure. Over.

073:28:25 Cernan: Okay. That's where we are right now, and I'm reading about 0.23 on my steam pressure.

[The Glycol Evaporator Steam Pressure meter on panel 2, provides indication of steam pressure in the water glycol evaporators. The Glycol Evaporator Temperature Outlet meter, also on panel 2, provides indication of the temperature of the water glycol at the outlet of the water glycol evaporator.]

Evap stm press P2

Glycol Evaporator Steam Press & Temp Outlet meters on panel 2.

Click on above image for full panel diagram.

073:28:33 Duke: Roger. We copy. Over...

073:28:34 Cernan: ...down, below, about 44 degrees. About 44 degrees on the Glycol Evap out Temp.

073:28:43 Duke: Roger.

[Comm break.]
PAO: Gene Cernan is reservcing the primary evaporator. That's the one that dried out in Earth orbit on launch day.

073:30:37 Duke: Hello, Houston - correction - Hello, Apollo 10. Houston. We have your final LOI-1 PAD ready to go and your P27 update. If you're ready to go with this, we are too. Over.

073:30:54 Stafford: Roger. I'll - For the P27 update, I'll go into CMC Accept now.

[The reference to CMC Accept means setting the Up Telemetry switch on panel 2 to Accept to enable the CMC to accept telemetry data from MCC-H.]
073:31:03 Duke: Roger.

073:31:05 Stafford: You're in Accept. Over.

073:31:09 Duke: Roger, 10. Out. [Pause.]

073:31:17 Cernan: Okay, Charlie. I'm ready for the final LOI-1, and make it a good one.

073:31:24 Duke: Roger, 10. This is LOI-1. SPS/G&N: 62554; plus 0.95, minus 0.17; 075:55:53.31; Noun 81 is minus 2913.8, minus 0561.2, minus 0229 – correction - 0299.7; 355, 230, 342; apogee is 0169.2, plus 0059.5; 2982.4, 5:54, 2975.2; sextant star is 16, 214.6, 39.4. The rest of the PAD is NA. Okay, your set stars are the same; your roll align is 241, 240 and 013; no ullage. The LM weight is the same. Over.

073:33:27 Cernan: Stand by one. [Long pause.]

073:34:44 Cernan: Houston, this is 10 with the readback.

073:34:47 Duke: Go ahead.

073:34:51 Cernan: LOI-1 is SPS/G&N: 62554, plus 0.95, minus 0.17; 075:55:53.31; minus 2913.8, minus 0561.2, minus 0299.7; 355, 230, 342; 0169.2, plus 0059.5; 2982.4, 5:54, 2975.2; 16, 214.6, 39.4; rest of PAD is NA. We've got Vega, 36; Deneb, 43; roll is 241, pitch is 240, yaw is 013; no ullage, and the LM weight is 30727.

[The above PAD is interpreted as follows:

Purpose: This PAD gives the parameters for Lunar Orbit Insertion burn number 1. This burn will decelerate Apollo 10 enough to cause it to be captured in an orbit around the Moon with a high apolune over the near side. This is to protect against an unintended overburn which could cause the spacecraft to impact the surface. A second burn, LOI-2, will be made after two revolutions to circularise this orbit.

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

CSM Weight (Noun 47): 62,554 pounds (28,439 kg).

Pitch and yaw trim (Noun 48): +0.95° and -0.17°. These are the initial angles to which the SPS engine should be swivelled to ensure its thrust acts through the combined spacecraft's centre of gravity. Once the burn begins, the engine's control system will steer the nozzle to compensate for c-of-g drifts.

Time of ignition, TIG (Noun 33): 75 hours, 55 minutes, 53.31 seconds.

Change in velocity (Noun 81), fps (m/s): X, -2,913.8 (-888.3); Y, -561.2 (-171.1); Z, -299.7 (-91.4). The change in velocity is resolved into three components expressed relative to the Local Vertical/Local Horizontal (LVLH) frame of reference.

Spacecraft attitude: Roll, 355°; Pitch, 230°; Yaw, 342°. The desired spacecraft attitude is measured relative to the alignment of the guidance platform.

HA, expected apocynthion of resulting orbit (Noun 44): 169.2 nautical miles (313.3 km).

HP, expected pericynthion of resulting orbit (Noun 44): 59.5 nautical miles (110.2 km).

The pericynthion will be over the Moon's far side, at roughly the same position that LOI occurred; with the apocynthion occurring over the near side.

Delta-VT: 2,982.4 fps (909.2 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, 54 seconds.

Delta-VC: 2,975.2 fps (907.0 m/s). This value is similar to the total change in velocity. It is entered into the Delta-V counter of the EMS (Entry Monitor System) panel. The crew monitor this figure as it descends to zero as the engine burns. If the Guidance and Control System fails to stop the burn, the EMS will do so but it has to be given a lower Delta-V figure to take account of the engine's tail-off thrust after shutdown.

Sextant star: Star 16 (Procyon) visible in sextant when shaft and trunnion angles are 214.6° and 39.4° respectively. This is part of an attitude check.

GDC align stars: Stars to be used for GDC align purposes are Vega (No 36) and Deneb (No 43). The align angles are roll, 241°; pitch, 240°; yaw, 13°. The purpose of this is to allow their backup gyros to be aligned in case the IMU fails. By viewing these two stars through the telescope and adjusting the spacecraft's attitude so they align with the reticle or graticule, the crew will know they are in the attitude stated, and can pass this onto the GDCs, the electronics that makes sense of the gyros output.

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

LM weight: 30,727 lbs (13,969 kg).]

073:36:10 Duke: That was a good readback, 10. Gene, how was my readup? Was it too slow, too fast, or - comments. Over.

073:36:21 Cernan: No. Very good, Charlie. Just right.

073:36:23 Duke: Roger. Out. [Pause.]

073:36:33 Stafford: Houston, Apollo 10. The uplink is coming through in good shape, and I wish you'd pass on to Jack Schmitt this message. The message is 'Would you believe the minimum stop on the 250-mm lens is 5.6. We do not have an f:4 on the 250mm. Over.

073:36:53 Duke: Roger, 10. We'll pass that on to him. And if no LOI-1 burn, you can expect AOS at 076:12:21.

073:37:19 Cernan: Okay. Without an LOI burn, AOS will be 076:12:21.

[The ground will be especially tuned to listen out for Acquisition Of Signal at this time, which would indicate no SPS burn at all. Acquisition at a time after this but prior to the expected full-burn AOS would indicate an underburn of the SPS engine which could result in some very exotic orbits, that in a worse case scenario may result in an impact on the lunar surface. The crew could employ one of the preplanned abort modes should there be an SPS engine malfunction. Because LOI always occurs behind the Moon, the crew must be able to evaluate the progress of the maneuver without ground support. Although two LOI burns are required to produce the desired 60-nautical mile altitude circular orbit, the monitoring requirements are defined primarily for the first burn (LOI-1), because the second burn (LOI-2) lasts for only approximately 15 seconds. The recommended LOI crew monitoring technique is depicted in figure below and is the same as for TLI.]

[For Apollo 10 (Mission F), the preignition spacecraft attitude check is made more difficult by the presence of the LM. However, the horizon and several stars should be visible from the CDR's rendezvous window and may be used as a backup to the optics for the orientation check prior to ignition. If the spacecraft attitude is not within ±5° of nominal, the LOI should be No-Go.]

[Although maintenance of crew safety is always the primary objective of monitoring procedures, an important second objective is the assurance that adequate abort capability is provided and is compatible with possible results of the monitoring procedures. The second objective was accomplished for LOI by definition of sound procedures for the four types of problems possible during LOI. Basically, the four problem areas are guidance and control, non-SPS systems, SPS, and inadvertent shutdowns. The recommended action for each problem is presented in table below. A solution for the first type of problem (guidance and control) would be to have the crew take manual control of the PGNCS-controlled maneuver and to complete the LOI at the original ignition attitude. One of the most dangerous possibilities associated with guidance and control problems could occur if the spacecraft IMU drifts during LOI. The crew cannot detect a small drift until an attitude deviation builds up and appears on the secondary inertial attitude reference system. Because the drift could have occurred in the secondary reference system as well as in the IMU, the crew would be unable to distinguish the erroneous system without the SCS attitude error needles (a third inertial reference system) which provides a tiebreaking capability. This detection of the error would make possible a manual takeover and completion of the burn so that the spacecraft could enter LPO (lunar parking orbit). Because uncorrected IMU drifts in pitch can produce impact trajectories, rules were developed to define attitude limits for which a takeover should be initiated.]

[The rules and limits require a manual takeover with the SCS at an attitude deviation of 10°, exclusive of start transients; the purpose of the 10° deviation is to prevent an undesirable pericynthion. A third inertial reference system is required during LOI to insure that the IMU does not cause an impact trajectory. Although there are three inertial reference systems in the spacecraft that could be used for LOI, an external reference system such as the lunar horizon or the stars may provide an additional reference system.]

LOI monitoring

LOI burn monitoring techniques.]

Type 1
Guidance & Control (IMU drifts, etc)

Manual takeover at 10°/sec or 10° attitude deviation and complete the LOI burn at the ignition attitude

Type 2
Non-SPS (ECS, etc) Complete the LOI burn
Type 3
SPS (Pressure off limits, steering, etc)

Crew chart abort SPS at 15 after cutoff or LM DPS at perilune using burn PAD from MCC-H read up after AOS

Type 4
Inadvertent shutdowns (CMC, etc) Attempt SPS restart or DPS abort 2 hours after cutoff using burn PAD from MCC-H read up after AOS
[List of actions to be taken in case of problems during LOI.

The LOI pitch or yaw rate limit is 10°/sec and results in a crew takeover and manual completion of LOI at ignition attitude.

Non-SPS problems require completion of LOI because it is advantageous to be in the planned lunar orbit rather than in any other orbit.

The SPS problems may dictate the necessity of an immediate abort maneuver which takes place 15 minutes after LOI ignition, after the crew terminates a nominal trajectory. Problems of this type are caused primarily by SPS problems which indicate that the SPS engine could have a limited burn time or maneuver capability. More specifically, serious SPS problems are as follows:

1. Sustained pressure decay in either fuel or oxidizer tank.
2. Thrust chamber pressure lower than 70 psi.
3. A delta pressure of greater than 20 psi between fuel and oxidizer tanks.

Although built-in redundancy may require two failures before the problems are time critical, the desire to complete the large abort maneuver (approximately 3,000 fps) as soon as possible to insure lunar sphere escape is the major justification for a 15-minute abort maneuver.

For inadvertent shutdowns, the crew will try a restart but if unsuccessful will prepare for a LM DPS abort.

Backup of the PGNCS LOI cut-off is performed by the crew primarily on a 10-second time bias to the nominal burn time also by monitoring the EMS Delta-V display.

In summary, guidance and control problems during LOI result in crew takeover and in burn completion to near-nominal LOI conditions, from which an abort could be initiated. The SPS problems will result in an early shutdown of the LOI burn and abort.]

073:37:24 Duke: Affirmative. Out. [Long pause.]

073:38:04 Duke: Hello, Apollo 10. Houston. We have your target load and state vector in. The computer is yours. Over.

073:38:15 Cernan: Okay. Thank you.

[Long comm break.]
PAO: This is Apollo Control at 73 hours, 38 minutes and we have just completed passing up the final Lunar Orbit Insertion burn PAD. It calls for an ignition time of 75 hours, 55 minutes, 53 seconds. A Delta-V of 2,982.4 feet per second [909.2 m/s]; duration of the burn 5 minutes, 54 seconds. That burn is targeted for an apocynthion of 169.2 nautical miles [313.4 km], with a pericynthion of 59.5 nautical miles [110.2 km]. Charlie Duke also passed up to Gene Cernan the acquisition time given no LOI burn. If the ESI [?] burn does not take place, we will acquire Apollo 10 at 76 hours, 12 minutes, 21 seconds. We had earlier passed up an acquisition time for a good LOI burn at 75 hours, 48 minutes, 25 seconds.

PAO: And the Environmental Control Officer William Burton has reported to Flight Director Gerry Griffin that he saw the evaporator take a drink and he feels warmer.

PAO: This is Apollo Control, with a correction. That last time I gave you is the LOS time 75:48:25. Acquisition time with a good LOI burn is 76:22:58. We'll continue to stay up live here, for any conversation. In the meantime, let me recap those times.

073:43:19 Duke: Hello, Apollo 10. Houston. Do you have any questions about the standard setting for the 250-millimeter lens in lunar orbit. Over.

073:43:31 Stafford: No. It looks like we're going to have to use an f:56 and 1/25 since the 250-mm lens doesn't have an f:4 on it.

073:43:39 Duke: Roger, Tom. I was just talking to Jack here, and he says we would like to use an f:5.6 at 1/250, except near the terminator, and then and then stop - then go down to 1/125. Over.

073:44:00 Stafford: Okay. We'll do that.

073:44:10 Duke: Roger.

[Very long comm break.]
PAO: This is Apollo Control. Apollo 10 will go behind the Moon and we will lose signal at 75 hours, 48 minutes, 25 seconds. If Apollo 10 does not do the LOI burn, we will reacquire the spacecraft at 76 hours, 12 minutes, 21 seconds. If the LOI burn is a good one, we will reacquire Apollo 10 at 76 hours, 22 minutes, 58 seconds. We now have clocks counting down in the Control Center to LOS and to ignition. We are showing 2 hours, 3 minutes, 10 seconds to Loss Of Signal; 2 hours, 10 minutes, 35 seconds to ignition.

PAO: This is Apollo Control at 73 hours, 56 minutes. Apollo 10 is 5,463 nautical miles [10,117 km] from the Moon. Velocity; 4,640 feet per second [1,414 m/s], Flight Dynamics Officer Phil Shaffer reports that at the time of Lunar Orbit Insertion, Apollo 10 will be 98.4 nautical miles [182.2 km] from the Moon and 215,847 nautical miles [399,746 km] from the Earth.

Flight Plan Page 3-39

074:13:35 Duke: Hello, Apollo 10. Houston. We'd like to give you a hack on your mission timer. Over.

074:13:43 Stafford: Go ahead, Houston.

074:13:45 Duke: Roger, 10. On my Mark it will be 74 hours, 14 minutes even. Stand by.

074:13:59 Duke: Mark.

074:14:00 Duke: 74:14.

074:14:05 Stafford: Roger. Houston, Apollo 10. We're synced right on with you.

[Stafford is ensuring the mission timer is correct.]
074:14:09 Duke: Roger.
[Long comm break.]
PAO: Charlie Duke gave Tom Stafford that mark 2 seconds early because Apollo 10 is at a distance now in which there in a 2-second delay in communications.

PAO: This is Apollo Control. There are five astronauts at the CapCom console at the present time. The two regular CapComs for this shift, Charlie Duke and Bruce McCandless, and in addition, Gordon Cooper, commander of the backup crew for Apollo 10; Ed Mitchell, the backup Lunar Module Pilot; and Dr. Jack Schmitt, the scientist/astronaut who is a geologist and who has worked with this crew on lunar geology.

074:21:01 Stafford: Houston, Apollo 10.

074:21:02 Duke: Go ahead, 10.

074:21:06 Stafford: Roger. Been reading our DSKY?

074:21:09 Duke: Roger. Sure have. That shows the star angle difference and the P52 and also the torquing angles. Over.

074:21:20 Stafford: Roger. Looks real good. We've also done our sextant star check, and we're right on. And, we've pulsed around here to the maneuver attitude, and we're just standing by.

074:21:32 Duke: Roger, 10. We show you in attitude. And, 10, Houston. We have an hour and 26 minutes to LOS. Over.

074:21:49 Stafford: Roger. 1 plus 26 to LOS. [Long pause.]

074:22:07 Stafford: Houston, Apollo 10. Do you have any updates as to when we'll have a sunrise on this pass?

074:22:16 Duke: Stand by. [Long pause.]

074:22:36 Duke: Hello, 10. Houston; We show sunrise at 74 hours and 50 minutes and 11 seconds. Over,

074:22:46 Stafford: Roger. 74:50:11.

[Very long comm break.]
074:41:48 Cernan: Hello, Houston. Apollo 10.

074:41:52 Duke: Go ahead, 10. Over.

074:42:01 Cernan: I cycled the cryo fans at about 71 hours. Should we go ahead and cycle them again before this burn?

[The cryo fans are in the cryogenic storage tanks serving the SM fuel cells.]
074:42:08 Duke: Stand by. [Long pause.]

074:42:57 Duke: Hello, Apollo 10. Houston. We'd like you to stir up the cryos again when you normally do it in the preburn checklist. Over.

074:43:07 Cernan: Okay. Fine. And, Houston, in looking at the Earth right now, looking at the South Atlantic off the coast of South America, in about the center of the globe, is a brilliant, bright, very, very bright reflective light. You can see it with the naked eye, and then again see it with the monocular; it's a very brilliant spot, just a spot, intense light from the Earth.

074:43:41 Duke: Roger. In the South Atlantic, 10? Over.

074:43:50 Cernan: Yes. I think it looks to me like it's right smack in the middle of the subsolar point. Just a continuous white, bright, brilliant light - just a pinpoint. [Long pause.]

PAO: This is Apollo Control at 74 hours and 44 minutes and Charlie Duke is talking to Gene Cernan.

074:44:17 Duke: 10, Houston. We'll check it out with the guys in the back, and see if they think that's the subsolar point or just a reflection – angle of incidence type thing. Over.

074:44:36 Cernan: I'm sure it's just a reflection, but it's the first time I've ever seen anything like that.

074:44:42 Duke: Roger. We'll see if we can come up with some ideas...

074:44:44 Cernan: As a matter of fact, it's - Okay. The brilliance of the light is just now fading, and it definitely is in the middle of the subsolar point and it's - the reflect - the reflection is totally gone at this time.

074:44:59 Duke: Roger. Copy.

074:45:04 Cernan: But what it was there was bright and brilliant.

074:45:08 Duke: Copy. Over. [Long pause.]

074:45:49 Duke: Hello, Apollo 10. Houston. We have two Comm switches for you that will put you in lunar orbit comm configuration. These are S-Band Auxiliary to Downvoice Backup and Tape Recorder Forward to Forward. Over.

[The communications configuration being suggested by MCC-H is to set the S-Band Auxiliary switch to Downvoice Backup. This selects the low bit rate premodulation baseband voice mode of transponder. Tape Recorder switch to Forward, in this position will allow the tape transport to run in the forward direction at 120 ips (inches per second, 305 cm/sec) if Play or Record is not selected.]

S-Band Aux Tape Fwd P1

S-Band Aux Down Voice Backup & Tape Recorder switches on panel 3.

Click on above image for full panel diagram.

074:46:10 Cernan: Roger, Charlie. Do you want those now?

074:46:14 Duke: That's affirmative, 10. Over. [Pause.]

074:46:23 Cernan: Okay. Tape Recorder to Forward; and I'll go Downvoice Backup. Does that also mean you want the Voice switch to Off?

074:46:35 Duke: That’s negative, 10. Over.

074:46:42 Cernan: Okey doke. We are now in Downvoice Backup; Tape Recorder is Forward and that was the only two changes.

074:46:49 Duke: That's affirmative, 10. And we've polled the room and you are Go for LOI. Over.

074:47:01 Cernan: Thank you.

[Long comm break.]
PAO: This is Apollo Control at 74 hours, 50 minutes. We are 58 minutes, 4 seconds away from Loss Of Signal when Apollo 10 will go behind the Moon. We are 1 hour, 5 minutes, 23 seconds from the LOI burn.

074:50:32 Young: Hello, sunshine - Here comes the sunshine.

074:50:39 Cooper: Well, we copy, 10. At 74:50 thereabouts.

074:50:48 Young: That's right. It's nice to have a little pad of darkness in there to go out there and do a good alignment where you can nicely recognize the constellations.

074:51:03 Cooper: Roger. We copy, 10.

074:51:09 Cooper: How do they compare with the CMS [Command Module Simulator]?

074:51:17 Young: These stars are better. [Long pause.]

PAO: That was John Young reporting sunrise.

074:51:32 Cooper: Would you like another reset point?

074:51:39 Young: We'll take one next time around, Gordo. I'll bet it looks like Vulture's Row down there today, doesn't it?

074:51:47 Cooper: Yes. You can’t stir them with a stick down here.

074:51:56 Stafford: We just turned a page in the Flight Plan, and we certainly appreciate the insert that you put in there.

074:52:03 Cooper: Roger. [Long pause.]

074:52:34 Stafford: Houston, Apollo 10. Now, we still have a beautiful view of the Earth right out through the center hatch window. It was just a little bit smaller than a tennis ball this morning; it's right now about the size of a hand ball.

074:52:49 Duke: Roger. We copy, 10. That's a pretty good eye.

074:52:55 Cernan: Don't let them kid you, Charlie; it looks like a dime to me.

PAO: That was Gene Cernan's comment there at the last.

074:53:05 Duke: Chris says when it gets to look the size of a squash ball, let him know.

074:53:15 Stafford: Roger.

[Very long comm break.]
PAO: The backup Command Module Pilot Donn Eisele has joined the rest of the backup crew here in the Control Room.

PAO: Apollo 10 is 3,012 miles [5,578 km] from the Moon. Velocity; 5,201 feet per second [1,585 m/s].

075:06:24 Duke: Hello, Apollo 10. Houston. We'd like you to select Omni Charlie so we can get a couple of minutes of high bit rate. Over.

075:06:59 Cernan: Houston, this is 10. You ought to have Omni Charlie now.

075:07:02 Duke: Roger, 10. We're reading you five-by. Out. [Long pause.]

075:09:15 Stafford: Houston, Apollo 10. We'll start through the P30-P40 series at approximately 75:30. Over.

[Program P30 External Delta-V program - to accept targeting parameters provided by MCC-H and compute from these the required velocity and other initial conditions required by the CMC to execute a maneuver. The targeting parameters input into the CMC are time of ignition (TIG) and the impulsive Delta-V along the CSM local vertical axes at TIG.]

[Program P40 SPS program - to compute the preferred IMU orientation and the preferred spacecraft attitude for an SPS thrusting maneuver and to maneuver the spacecraft to this attitude. To control the GNCS during the countdown, ignition, thrusting and thrust termination of a GNCS controlled SPS maneuver.]

075:09:24 Duke: Roger, 10. We copy. We'll he watching.

075:09:27 Cernan: Okay, Charlie.

[Very long comm break.]
PAO: This is Apollo Control at 75 hours, 14 minutes. Apollo 10 is 1,892 miles [3,504 km] from the Moon. Lunar reference velocity; 5,723 feet per second [1,745 m/s]. We're 34 minutes away from Loss Of Signal, and a little over 41 minutes away from the Lunar Orbit Insertion burn.

PAO: This is Apollo Control at 75 hours, 29 minutes. Apollo 10 is 1,134 nautical miles [2,100 km] from the Moon. Lunar reference to velocity; 6,345 feet per second [1,934 m/s]. Tom Stafford has just informed us that he is going into some of the computer programs preparatory to the LOI burn.

075:29:27 Stafford: Houston, Apollo 10. We'll start through the P30-P40 series now. Over.

075:29:30 Duke: Roger, 10. Standing By. Over. [Long pause.]

075:30:10 Stafford: Okay. And we know what that is. That is due to the conic integration.

075:30:16 Duke: Roger.

[Long comm break.]
PAO: The Command Module Computer is now in program 40, the Service Propulsion System thrusting program, as the Apollo 10 crew gets prepared for the Lunar Orbit Insertion number 1 burn which will take place 22 minutes, 20 seconds from now. They will be behind the Moon at that time; beyond the contact with the Earth. Loss Of Signal; 14 minutes, 39 seconds from now. Apollo 10 is reported to be maneuvering to burn attitude at this time. The LOI maneuver will be a retrograde burn with the spacecraft pitched up 22 degrees. There will also be some out-of-plane component in this burn to take care of the rest of the maneuver needed to place Apollo 10 on the proper inclination across the lunar equator. The first part of this maneuver was done during midcourse burn, be completed during the LOI burn.

075:35:33 Stafford: Houston, Apollo 10 [garble] we can read our DSKY. We've trimmed and we're in a trim attitude and, as far as our checklist, we're minus 6 minutes and waiting.

075:35:44 Duke: Roger. We copy, 10. We have you holding at minus 6 minutes. [Long pause.]

075:35:58 Duke: 10, Houston. One reminder. We really – on the high bit rate, it's 30 seconds. Over. Before for the burn.

075:36:10 Stafford: Roger. Understand. Go to high bit rate. We've got that on our checklist, but we'll make sure we go there 30 seconds prior to the burn.

[The onboard Data Storage Equipment (DSE) is set to record onboard data from 30 seconds prior to the LOI-1 SPS ignition. It is commanded to high-bit-rate recording by placing the PCM (Pulse Code Modulation) Bit Rate switch on panel 3 to the High position. In the High position the tape is fed at 15 ips (37.5 cm/sec).]

PCM Bit rate sw P3

PCM Bit Rate switch on panel 3.

Click on above image for full panel diagram.

075:36:17 Duke: Roger.
[Comm break.]
PAO: Following a good LOI burn, Apollo 10 will be on the exact ground track that Apollo 11 will have.

075:37:22 Young: Houston, we've got a bunch of clocks running in here; but just in case, give us a sync hack in 10 minutes, will you?

075:37:29 Duke: Roger. We’ll give you a hack at 10 minutes. Over.

[Long comm break.]
PAO: Apollo 10 is now 9 minutes away from Loss Of Signal. It's distance from the Moon is 681 nautical miles [1,261 km]. Velocity; 6,916 feet per second [2,108 m/s].

075:41:24 Stafford: Houston, Apollo 10. Just tried looking out as far as I can out the top hatch window, and still can't see the Moon; but we’ll take your word that it’s there. Over.

075:41:33 Duke: Roger, 10. That's guaranteed it's there. Over.

075:41:40 Young: Okay. [Pause.]

PAO: That was a trusting Tom Stafford.

075:41:50 Cernan: We know it's there. I hope it's there plus 60 miles [111 km].

075:41:54 Young: No guarantee on that.

075:42:00 Duke: Our Trench guys guarantee 60 by 170 [111 by 315 km] on your - if you can burn on the P40 number.

075:42:09 Cernan: Man, the beer's on me, if it's 60 by 170 [111 by 315 km].

075:42:16 Duke: We'll take that.

075:42:21 Cernan: And if it ain't, we don't have to worry, about it.

[Comm break.]
PAO: That was Gene Cernan.

PAO: And we're coming up on 3 minutes to Loss Of Signal. Mark. 3 minutes.

[The crew have activated the onboard recorder in anticipation of LOS as they pass behind the Moon for the first time.]
075:42:53 Young (onboard): Which one, Tom?

075:42:54 Stafford (onboard): [Garble] I got [garble]. It'll probably come down during the burn.

075:43:05 Young (onboard): Ain't going to pull a quarter of a g.

075:43:20 Young (onboard): And - and when do we lose them - at - at 48, huh?

075:43:28 Cernan (onboard): Yes, 48.

075:43:30 Young (onboard): 48 what? 50 something?

075:43:34 Cernan (onboard): 48 - Tom's got it there - 25...

075:43:36 Stafford (onboard): Do they want us to proceed to be in that [garble] 60 40 before we lose them?

075:43:40 Young (onboard): No, I don't want to do that.

075:43:44 Stafford (onboard): [Garble] to have a little gimbal [garble].

075:43:49 Young (onboard): We can't; we got to turn on the gimb - we have - turn on the - run through the gimbal drive check.

075:43:52 Stafford (onboard): Yes, yes.

075:44:01 Young (onboard): This is what's important, if it comes out at that angle. That's it; the gauge right there.

075:44:05 Stafford (onboard): Yes.

075:45:26 Duke: Apollo 10, Houston. On my Mark, it'll be 10 minutes to ignition. Over.

075:45:34 Young: 10. Roger. [Pause.]

075:45:45 Duke: Apollo 10, stand by for a Mark, 10 minutes.

075:45:52 Duke: Mark.

075:45:53 Duke: Ten minutes to ignition.

075:45:57 Young: We're synced.

075:45:58 Duke: Roger. [Long pause.]

PAO: And again he gave you that mark 2 seconds early to allow for the lag time in communications.

[The crew now beginning calling out the switch and circuit breaker settings as they work their way through the pre-LOI burn checklist.]
075:46:01 Cernan (onboard): Okay, let's go do it.

075:46:19 Cernan (onboard): Okay. The BMAGs were On; the SCS Electronics, On...

075:46:22 Duke: Apollo 10, Houston...

075:46:23 Cernan (onboard): ...[garble] power's On...

[The two BMAG Power switches on panel 7 provide 28V DC to both of the Gyro Assemblies (GA) for heating and operation electronics plus 3 phase AC. The SCS Electronics Power rotary switch is set to GDC/ECA. In this position DC and AC power is supplied to the GDC and route the SCS logic bus power to panel 1 switches.]


SCS and BMG Power rotary switches on panel 7.

Click on above image for full panel diagram.

[MP3 audio file.]

075:46:24 Duke: Two minutes to LOS; everybody here says "God speed."

075:46:30 Stafford: Okay, and we'll see them right on the other side in orbit.

075:46:33 Duke: Roger. 76:22:55.

[This is the Acquisition Of Signal time following a successful LOI-1 SPS burn.]
075:46:39 Stafford: We'll be calling you.
[Very long comm break.]
PAO: There's LOS right on the numbers. And as Apollo 10 and its crew goes behind the Moon, they're 7 minutes, 16 seconds away from the Lunar Orbit Insertion burn. That burn scheduled for 75 hours, 55 minutes, 53 seconds. Total Delta-V of 2,982.4 feet per second [909.2 m/s]. Burn time of 5:54, 5 minutes, 54 seconds.

075:46:47 Stafford (onboard): Okay. I'll put this under my back, back here, Gene-o.

075:46:51 Cernan (onboard): Okay.

075:46:52 Stafford (onboard): The criteria for overburn is 10 seconds. At Loss Of Signal, you got the DSE [Data Storage Equipment] - if no DSE motion, go to [garble] Command Reset then Normal. You got that?

[The overburn criteria of 10 seconds is the mission rule that the crew must manually shut down the SPS engine should it still be burning 10 seconds after the predicted cut-off. They will monitor the burn-time and Delta-V change using the EMS.]

[The DSE should be recording at Loss Of Signal (LOS). If not, the crew must move the spring loaded Up Telemetry switch on panel 3 to the Command Reset position and it will then return to the Normal position. Setting this switch briefly to CMD Reset performs a real-time Command Reset function and maintains the power supply. This resets all read time commands (RTC) relays except those relays affecting the system A abort light and the crew alarm so the affected equipment will resume the operational mode dictated by their control switches on the panel 3.]


Up Telemetry Command Reset switch on panel 3.

Click on above image for full panel diagram.

075:47:03 Cernan (onboard): Okay there it is, we've got it, so we're okay.

075:47:05 Stafford (onboard): Yes, okay. The only thing we've got left now is - to go...

075:47:12 Cernan (onboard): You're on - you're on tape by the way.

075:47:14 Stafford (onboard): That checks. Okay, we're on tape.

075:47:15 Young (onboard): You're on High Bit Rate now?

[High Bit Rate on the DSE.]
075:47:16 Cernan (onboard): No, but we got the DSE running.

075:47:18 Young (onboard): Okay, I'm going to run through these checks just one more time...

075:47:20 Cernan (onboard): Yes, go ahead.

075:47:21 Young (onboard): ...the EMS Delta-V check; the EMS Delta-V is set. 2975.2, right?

[As set out in the LOI-1 PAD previously, the EMS Delta-VC value of 2,975.2 fps [907.0 m/s] is entered into the Delta-V display of the EMS (Entry Monitor System) panel. The crew monitor this figure as it descends to zero as the engine burns. If the Guidance and Control System fails to stop the burn, the EMS will do so but it has to be given a lower Delta-V figure to take account of the engine's tail-off thrust after shutdown. The EMS switches and displays are situated at the top of Main Display Panel 1.]

EMS SPS monitoring

EMS switches and displays used to monitor SPS burns on panel 1.

Click on above image for full panel diagram.

[The EMS function switch is placed in the Vo SET position which enables the Delta-V/Range display to be set to the desired figure using the Delta-V/EMS Set switch.

075:47:26 Stafford (onboard): Yes.

075:47:27 Young (onboard): BMAGs, three, to Rate 2; go. LM/CM, Delta-V CG, no RCS Selects are set.

[BMAG Rate 2 switch is set for each of the three axes; roll, pitch and yaw, a ensures the BMAG output is not utilized. The Delta-V CG switch on panel 1 is set to LM/CM enables body-bending filters in the SCS Auto TVC control path.]

Delta-V CG switch P1

Click on above image for full panel diagram.

[No Auto RCS Select switches have yet been set to select the required RCS quads and the buses they will be tied to.]

075:47:34 Cernan (onboard): [Cough].

075:47:35 Young (onboard): The DAP is set and loaded.

[The CM DAP has been set to support the upcoming LOI burn using the CMC routine R03 detailed below.

Routine R03-Digital Autopilot Data Load

  1. To load and verify the CMC DAP
  2. To provide the crew a means for selecting appropriate coast autopilots, after completion of this routine, which identifies the vehicle configuration, the use of Verb 46 Enter (“establish GNC control”) will cause the appropriate DAP to become active.
Key Verb 48 Enter to commence the R03 routine to load the DAP.

Verb and Noun displays flash to request crew input and display the DAP configuration data Verb 04 Noun 46 Enter:
Register 1 (R1): ABCDE
Register 2 (R2): ABCDE
Register 3 (R3): BLANK

R1 data code:
A-vehicle configuration:
0-No DAP
1-CSM only
2-CSM + LM (Ascent & Descent stages)
6-CSM + LM (Ascent stage only)

B-Quads AC for +X translation code:
0-Don’t use quads
1-Use quads

C-Quads BD for +X translation code:
0-Don’t use quads
1-Use quads

D-Deadband code:
0-0.5 deg
1-5.0 deg

E-(USB) maneuver rate code:
0-0.05 deg/sec
1-0.2 deg/sec
2-0.5 deg/sec
3-4.0 deg/sec

R2 data code
A-AC or BD roll code
0-Use BD quads
1-Use AC quads

B-Quad A code
0-Don’t use
1-Use quad

C-Quad B code
0-Don’t use
1-Use quad

D-Quad C code
0-Don’t use
1-Use quad

E-Quad D code
0-Don’t use
1-Use quad

If satisfied with existing DAP configuration codes, key in Proceed.

If not satisfied with existing DAP configuration codes, key Verb 21 Enter to load the desired R1 code, Verb 22 Enter to load the desired R2 code.

A flashing Verb/Noun request for crew to respond with CSM and LM weights.
Verb 06 (display decimal in R1 & R2) Noun 47 (R1 this vehicle weight XXXXX. lbs, R2 other vehicle weight XXXXX. Lbs).

R1-CSM weight
R2-LM weight

Both weights in pounds to the nearest pound.

Is the LM attached?

If Yes, are the weights entered for both vehicles correct? Key Proceed.
If No, is the weight entered for the CSM correct? If YES key Proceed.

If the weights entered are incorrect, reload using Verb 21 (CSM only) or Verb 22 (CSM & LM) Enter then key Proceed

Flashing will terminate.

Flashing Verb 06 (display decimal in R1 & R2) Noun 48 (Gimbal pitch trim XXX.XX deg, Gimbal yaw trim XXX.XX deg)

R1-Pitch trim
R2-Yaw trim

If displayed values agree with expected values, key Proceed. If they are incorrect, load using Verb 21 or 22 Enter then key Proceed.

Data will now be transferred to the digital autopilot and routine R03 will be exited.]

075:47:36 Cernan (onboard): Yes.

075:47:37 Young (onboard): Spacecraft Control, CMC and Auto.

[The SC Cont switch on panel 1 is set to the CMC position to inhibit spacecraft control functions by the SCS. When the spacecraft is under CMC control, a translation command by the crew using the translation controller, results in a logic signal (28V DC) being sent to the CMC. The CMC would provide a translation command to the roll jets. The crew can immediately switch to SCS control if required by rotating the translation controller clockwise 17°.]

[The CMC Mode switch is set to Auto to enable the computer to control the spacecraft's attitude during the LOI burn.]


Click on above image for full panel diagram.

075:47:39 Cernan (onboard): Yes.

075:47:40 Young (onboard): Maneuver to burn attitude - we've done that; we've done that - boresight star; we've done the sextant star check; we done - we ain't got no boresight star, come to think of it. We've maneuvered to the attitude; panel 8, SCS breakers are Closed...

LOI attitude

[Spacecraft attitude during the LOI burn and the initial part of lunar orbit 1. This document is from the final Flight Plan. The times shown should be amended by adding 11 minutes due to the slightly later than planned lunar arrival due the cancellation of midcourse correction 3 as unnecessary.]

[The SCS breakers are the 4 SCS Logic Bus circuit breakers on panel 8 which supply 28V DC power over the main power buses A & B to the SCS logic (command) buses (circuits). These logic buses were used to send commands to the RCS, TVC (Thrust Vector Control) gimbals to steer the SPS engine, the Flight Director Attitude Indicator (FDAI) display and the Body Mounted Attitude Gyros (BMAG), if SCS control is required.]

SCS Logic cb P8

The SCS Logic Bus circuit breakers on panel 8.

Click on above image for full panel diagram.

075:47:56 Stafford (onboard): Are Closed. [Garble] okay.

075:47:58 Young (onboard): Manual Attitude, three, Rate Command is Go. Limit Cycle switch is Off - Doesn't make any difference...

[The Manual Attitude switch on panel 1 is placed in the Rate Command position to provide the capability to command spacecraft attitude translation rates that are proportional to the rotation controller (RC) deflection. If there is no deflection of the RC the spacecraft will be under automatic control.


Manual Attitude, Limit Cycle, Att Deadband Rate and Trans Contr PWR switches on panel 1.

Click on above image for full panel diagram.

[The Limit Cycle switch also on panel 1 is set to the Off position. It is placed in this position to conserve RCS propellant by allowing manual proportional rate command and automatic rate damping. If it was left in the up (On) position the spacecraft would be attitude hold mode, which is propellant expensive.]

075:48:03 Stafford (onboard): [Garble.]

075:48:04 Young (onboard): Deadband, Min Rate is High. Translation Control Power is On, in case we have to get Att through the SCS; AC 1, okay; Rotational Control Power, Directs, are Off; Spacecraft Control, CMC and Auto again; SCS TVCs in Rate Command; TVC Gimbal Drives in Auto. And wait for 6 minutes. That was Loss Of Signal right there.

[The Att Deadband and Rate switch positions establish rate and deadband response. With the Att Deadband switch placed in the Min position, it switches the electrical deadband out of the Electronic Control Assembly (ECA) attitude control loop in all 3 axes. The Rate switch is set to High to set the attitude rates (see below).]

Attitude rates

[The Translation Control Power switch is set to On to allow use of this controller in all 3 axes. SCS-TVC Servo Power switch on panel 7, is set to AC1 to provide AC power over AC power bus 1 and DC power over main power bus A to the Trust Vector Control (TVC) servos in both pitch & yaw.]


TVC power switch on panel 7.

Click on above image for full panel diagram.

[Rotational Control Power-Direct, are both set to off. This removes all DC and AC power from the controller.


Rotation Controller Power switches on panel 1.

Click on above image for full panel diagram.

[John Young has repeated the instruction regarding the Spacecraft Control and CMC Mode which he called out at 075:47:37. SCS TVCs in Rate Command on panel 1 allows thrust vector control to be switched to SCS control as a backup to the CMC. This both in pitch and yaw.]


SCS TVC switches on panel 1.

Click on above image for full panel diagram.

[TVC Gimbal Drive in Auto provides an automatic transfer from servo 1 to servo 2 if either a Translation Controller-Clockwise motion is made or an over-current logic signal is sent from the SPS.]


TVC Gimbal Drive switches on panel 1.

Click on above image for full panel diagram.

[Young also is noting that they have had Loss Of Signal between the combined spacecraft and the Earth as they finally swing behind the Moon for the first time, just prior to the planned LOI burn.]

075:48:26 Cernan (onboard): Yes. Yes, that was it, babe.

075:48:27 Young (onboard): That was it! Lost it.

075:48:30 Stafford (onboard): We're on our own now.

075:48:32 Cernan (onboard): You see anything over the top, Tom?

075:48:33 Stafford (onboard): No. Sure I'm not even going to look.

075:48:34 Cernan (onboard): Did you hear that? Man, we lost them in a hurry.

075:48:36 Young (onboard): Yes, it went off in a hurry.

075:48:38 Cernan (onboard): What's the configuration in the Flight Plan for acquiring them around the other side; does it say, Tom? I'll go into that - Oh, that's the High Gain, right?

075:48:44 Stafford (onboard): Right.

075:48:45 Cernan (onboard): We'll be in a special, attitude, and I'll be able to pick them up High Gain, right?

075:48:48 Stafford (onboard): We roll 180, pitch...

075:48:50 Cernan (onboard): And then High Gain.

075:48:51 Stafford (onboard): ...pitch is minus 86, yaw is zero.

[HGA steering angles.]
075:48:54 Cernan (onboard): Verb 64, acquire for MSFN. Okay, fine; I'm all set.

075:48:58 Stafford (onboard): Okay, you've got a minus 86 degrees - -

075:49:00 Cernan (onboard): I got it in there.

075:49:01 Stafford (onboard): Okay. And minus - yaw is - is - -

075:49:02 Cernan (onboard): Okay.

[Cernan is ensuring the communications settings onboard are ready for acquisition of signal (AOS) when the spacecraft emerges from behind the Moon as seen from Earth. Stafford has given him the steering angles (Pitch -86°, Yaw 0°) for the high gain antenna, so that it is oriented correctly to get a strong lock on to the signal from the Earth MSFN station. Using CMC Verb 64 (request S-band antenna routine) to run routine R05, the CMC can calculate and display the S-band antenna gimbal angles required to point the antenna at the center of the Earth.]
075:49:03 Stafford (onboard): ...minus 7. Okay. Now, let me see just - again, the EMS is in, the RCS Logic - we got the helium - the pilot valves are in. All those good things are in...
[The CM RCS switch must be in Logic position (up) before power is available to the CM Prplnt Dump, Purge, and CM RCS Htrs switches, and circuitry controlling automatic transfer of engine firing command from SM RCS to CM RCS.]


CM RCS switch on panel 1.

Click on above image for full panel diagram.

[The EMS was set previously to monitor the LOI Delta-V at 075:47:21. There are two Helium SPS Helium Valve circuit breakers on panel 8, which provide DC power on main bus A to 2 SPS He Valve switches and the talkback indicators for these switches, which are all on panel 3. When both switches are set to the Auto position, the valve opening is controlled by the thrust On-Off signal from either the CMC or SCS. The valve position is indicated by the talkback indicator above the switches; barberpole indicates closed, gray indicates open. The helium is used to pressurize the SPS fuel and oxidiser tanks. The helium tank pressure is monitored on the strip meter at the top of panel 3.


SPS He Valve switches and He pressure meter on panel 3.

Click on above image for full panel diagram.

[The two Pilot Valve circuit breakers on panel 8 are pushed in to provide power to the Delta-V Thrust Normal switch via both DC power buses.]


Helium Valve and Pilot Valve circuit breakers on panel 8.

Click on above image for full panel diagram.

075:49:12 Young (onboard): Yes, all those things are in because if they ain't, nothing happens.

075:49:16 Stafford (onboard): Yes.

075:49:17 Cernan (onboard): Okay, we got the Bus Ties to go over here.

075:49:19 Stafford (onboard): Okay, and we got the Bat Relay Bus and all those.

[The battery relay bus provides DC power to the AC sensing units, the fuel cell and inverter control circuits, fuel cell reactant and radiator valves and the fuel cell main bus A and B talkback indicators.]


Bat Relay Bus circuit breakers on panel 5.

Click on above image for full panel diagram.

075:49:22 Cernan (onboard): That's all in. Everything that I can see over here is in that should be in.

075:49:26 Stafford (onboard): Okay, we're up to 6 minutes.

075:49:28 Cernan (onboard): And, John, I'll give you a call through mode 1, mode 2, and...

[Cernan is referring to the LOI abort modes detailed at 073:37:19]
075:50:19 Young (onboard): Roger.

075:50:20 Stafford (onboard): You want to go ahead and be ahead of it? Or not?

075:50:22 Young (onboard): I don't see much sense in doing it.

075:50:36 Cernan (onboard): Oh, dear.

075:50:47 Stafford (onboard): Okay.

075:50:48 Stafford (onboard): Okay, 5 minutes, Gimbal...

075:50:49 Young (onboard): Pitch Motor number 1 is coming On, Gene-o.

075:50:52 Cernan (onboard): Okay, stand by. Go. That's go.

075:50:56 Stafford (onboard): Yaw 1.

075:50:57 Young (onboard): Yaw 1 is coming On.

[The Pitch and Yaw SPS Gimbal Motor switches are in a single bank on panel 1. The three position toggle switch with upper (Start) position spring-loaded to return the switch to the center position when released. Pitch 1 and Yaw 1 switches control the gimbal actuator primary drive motors. The Pitch 2 and Yaw 2 switches control the gimbal actuator secondary drive motors.]

SPS Gimbal Motors P1

SPS Gimbal Motors, Pitch and Yaw on panel 1.

Click on above image for full panel diagram.

075:50:58 Cernan (onboard): That's go.

075:50:59 Stafford (onboard): Translational Control, clockwise...

075:51:00 Young (onboard): Translational Control, clockwise.

075:51:03 Stafford (onboard): ...verify no MTVC.

075:51:04 Young (onboard): We have no MTVC.

[MTVC - Manual Thrust Vector Control. Rotational Controller clockwise action signals are used to command spacecraft rotation rates during SCS proportional rate control and to command SPS engine gimbal position during manual thrust vector control. The manual proportional commands to the TVC are input via the rotation controller. The crew is checking that the TVC is under the control of the CMC.]
075:51:05 Stafford (onboard): Check TVC - secondary TVC check; Pitch 2.

075:51:09 Young (onboard): Coming On, Gene-o.

075:51:10 Young (onboard): Mark.

075:51:11 Cernan (onboard): That's go.

075:51:12 Stafford (onboard): Yaw 2, Start.

075:51:13 Young (onboard): Yaw 2, coming On.

[Pitch 2 and Yaw 2 SPS Gimbal Motors have now been set to start.]
075:51:15 Cernan (onboard): That's go.

075:51:16 Stafford (onboard): Set the trim.

075:51:17 Cernan (onboard): Should have all four, babe...

075:51:18 Young (onboard): Plus 95.

075:51:19 Stafford (onboard): And minus 17.

075:51:20 Young (onboard): Minus 17.

[Gimbal trim angles, 0.95° pitch and 0.17° yaw.]
075:51:22 Stafford (onboard): Okay.

075:51:23 Young (onboard): Okay.

[In SCS Delta-V mode, manual SPS engine gimbal trim capability is provided. Desired gimbal trim angles are set with the pitch and yaw trim thumbwheels on panel 1. The indicator displays SPS engine position relative to actuator null and not body axes. The range of the engine pitch and yaw gimbal displays are ±4.5°. This range is graduated with marks at each 0.5° and reference numeral at each 2° division. The range of the fuel pressure scale is 0 to 50 psi with graduations at each 5-psi division, and reference numerals at each 10-psi division.]

SPS Gimbal trim panel P1

SPS Gimbal trim panel

SPS Gimbal trim P1

SPS gimbal trim thumb wheels and Gimbal Position Indicator (GPI) displays on panel 1.

Click on above image for full panel diagram.

075:51:24 Stafford (onboard): Check MTVC, would you, John? Something's shaking.

075:51:31 Cernan (onboard): That's got...

075:51:32 Young (onboard): The old big bell, babe. GPI to neutral.

075:51:34 Stafford (onboard): GPI to neutral.

075:51:35 Young (onboard): Go to zero.

[Young is saying the gimbal position indicator needs to be set to the neutral position using the translation controller.]
075:51:37 Stafford (onboard): Rotational Control Power, number 2, AC/DC.
[Provides 28V DC via main buses A & B and 26V AC via AC bus 1 to rotation controller 2.]

Rot Cntrl Pwr Norm P1

Rotation Controller power switches on panel 1.

Click on above image for full panel diagram.

075:51:41 Young (onboard): AC/DC. We checked the boresight star?

075:51:42 Stafford (onboard): We don't have that?

075:51:43 Young (onboard): Okay, Auto gimbal check.

075:51:45 Stafford (onboard): Okay. Oh, do you want one final trim here?

075:51:48 Cernan (onboard): No. We don't need that.

075:51:51 Young (onboard): Yes. There you go.

075:51:56 Stafford (onboard): Okay, Enter?

075:51:57 Young (onboard): Enter.

075:51:58 Cernan (onboard): You're back in neutral on your controller, huh?

[Translation controller to its neutral position.]
075:51:59 Stafford/Young (onboard): Yes.

075:52:00 Cernan (onboard): Okay.

075:52:01 Stafford (onboard): 204, ready?

075:52:02 Young (onboard): Yes.

075:52:03 Stafford (onboard): Plus 2, minus 2, and zero. Plus 2, minus 2, and a zero.

[Stafford is manually testing the SPS pitch and yaw gimbals by ±2°.]
075:52:13 Cernan (onboard): Oh, I tell you; that mother really moves around, doesn't it?

075:52:16 Young (onboard): Trim that moves it.

075:52:21 Cernan (onboard): Okay, y'all.

075:52:22 Stafford (onboard): 03:30. Okay, 6 [garble] 40 okay - Rotational Control Power, Direct, MN A/MN B.

[3 minutes and 30 seconds to LOI ignition. The Rotational Control Power switches are being set to Direct via both DC buses. This enables direct manual control of the RCS once the rotation controller has been deflected by 11 degrees in any axes.]


Rotation Controller Power Direct switches on panel 1.

Click on above image for full panel diagram.

075:52:29 Young (onboard): That's go.

075:52:30 Stafford (onboard): SPS Helium Valves, two, Auto.

075:52:31 Young (onboard): They are Auto. Limit Cycle switch to Off.

[With both SPS Helium Valves switches set to Auto, the supply of power to the valves is controlled by the CMC, SCS or SPS Thrust Direct, On switch.]


SPS He Valves-Auto switches on panel 3.

Click on above image for full panel diagram.

075:52:33 Stafford (onboard): Limit Cycle switch is Off. FDAI is what you wanted?
[The crew are confirming the Limit Cycle switch is Off which they set at 075:47:58]
075:52:35 Young (onboard): Yes. GDC Align, right?

075:52:37 Stafford (onboard): Yes, GDC Align.

[GDC Align pushbutton on panel 1, provides a means of aligning the Gyro Display Coupler (GDC) to a given reference. The GDC has two gyro assemblies associated with it, which can provide attitude determination. They are normally aligned to match the current IMU orientation. This provides a backup attitude reference in case of an IMU malfunction.]

GDC Align pb P1

GDC Align push button on panel 1.

Click on above image for full panel diagram.

075:52:40 Young (onboard): I've got 351 here, now.
[Spacecraft currently at 351° roll angle. 355° is the planned roll attitude at LOI ignition.]
075:52:46 Stafford (onboard): Coming in.

075:52:51 Young (onboard): Okay.

075:52:52 Stafford (onboard): BMAGs, three, Att 1/Rate 2.

[With the BMAG Mode switches (one in each axes) in the Att 1/Rate 2 position the BMAG in GA-2 provides rate signals for control and display, plus GDC update. The BMAG in GA-1 provides attitude error signals for control and display.]


Three BMAG Mode switches on panel 1.

Click on above image for full panel diagram.

075:52:55 Young (onboard): Okay.

PAO: Mark. 3 minutes to LOI burn. We won't know how this maneuver has gone until we acquire Apollo 10 as it comes around the front of the Moon.

075:52:58 Stafford (onboard): Okay, minus 2 minutes, John.

075:53:04 Cernan (onboard): Still don't see nothing, huh, Tom?

075:53:06 Stafford (onboard): Shit, no! And I don't care to see anything now. Not much to see...

075:53:09 Cernan (onboard): Okay, your trim's set, John?

075:53:11 Young/Stafford (onboard): Yes.

075:53:18 Cernan (onboard): Was it plus 0.95 and a minus 0.17?

[The SPS gimbal trim angles of plus 0.95° pitch and minus 0.17° yaw are those read up to the crew as part of the LOI PAD at 073:34:51.]
075:53:21 Young (onboard): Yes.

075:53:22 Cernan (onboard): Okay.

075:53:23 Stafford (onboard): Okay, at 2 minutes, Delta-V Thrust, A and B, Normal.

075:53:27 Young (onboard): A, Normal, right?

075:53:28 Stafford (onboard): A, Normal. You can get the guard up on B.

[Both of the Delta-V Thrust switches on panel 1 are covered by flip up guards to prevent inadvertent use. These switches provide an SPS-ready signal to the GDC and provide power to the Flight Combustion Stability Monitor (FCSM), and the SPS valves via both main power buses.

Thrust A B P1

Delta-V Thrust switches on panel 1.

Click on above image for full panel diagram.

[SPS ignition will only occur with the Delta-V Thrust A switch in the Normal position.]

075:53:44 Cernan (onboard): Sure is getting bright out there. I got the Moon's reflected surface in the LM window. I can see it in the LM window, the overhead window.

075:53:52 Stafford (onboard): Good show.

075:53:53 Cernan (onboard): It's down there, babe.

075:53:54 Stafford (onboard): Okay, 2 minutes, Delta-V Thrust, A, Normal; Translational Control Power, Armed.

075:53:59 Young (onboard): Translational Control Power is Armed.

075:54:01 Cernan (onboard): Look at the size of...

075:54:02 Young (onboard): Rotational Control Power is Armed. Okay, at 30 seconds...

075:54:05 Stafford (onboard): You don't have the Translation Armed.

[The Translational Control Power switch on panel 1 provides 28V DC power to the controller via both main power buses. Young actually powers up the rotational controller which was the next step on the checklist. Stafford double checks the actions and catches the small error.]

Trans Ctrl Pwr P1

Translational Control Power switch on panel 1.

Click on above image for full panel diagram.

075:54:07 Young (onboard): Yes, it is. No, there you go.

075:54:08 Stafford (onboard): Okay, at 30 seconds, EMS, Normal, and Delta - EMS Delta-V, Normal, and High Bit Rate.

[EMS Mode switch on panel 1 is set to Normal <30 seconds prior to thrusting to minimize buildup of Delta-V indicator errors, caused by accelerometer bias. The Rate switch on panel 1 selects low gains in both rate and attitude in all axes, and high gain in roll manual control.]


EMS Mode switch on panel 1.

Click on above image for full panel diagram.

RATE switch P1

Rate switch on panel 1.

Click on above image for full panel diagram.

075:54:14 Cernan (onboard): Okay, I'm really for it. God, that Moon is beautiful; we're right on top of it...

075:54:19 Stafford (onboard): Oh, shit!

075:54:20 Cernan (onboard): God dang. We're right on top of it. I can see it...

075:54:22 Stafford (onboard): Oh, shit; John! It looks like a big plaster-of-paris cast.

075:54:24 Cernan (onboard): I can see it reflected, babe - right in the LM overhead window.

075:54:29 Stafford (onboard): Okay, let's get busy...

075:54:30 Cernan (onboard): Okay, let's get this burn off. How much time?

075:54:35 Stafford (onboard): 1 minute and...

075:54:36 Cernan (onboard): 1 minute and 20, right? Okay.

075:54:37 Stafford (onboard): Oh, yes.

075:54:38 Cernan (onboard): You got it, Tom?

075:54:39 Stafford (onboard): You damn right I got it.

075:54:42 Cernan (onboard): Oh, I do, too.

075:54:43 Stafford (onboard): Okay, let's keep looking then.

075:54:44 Cernan (onboard): My God, that's incredible.

075:54:46 Stafford (onboard): It looks like we're close...

075:54:47 Cernan (onboard): That's incredible.

075:54:49 Stafford (onboard): It does look like we're - well, we're about 60 miles, I guess.

075:54:51 Stafford (onboard): Okay, 1 minute. Okay, let's go.

075:54:54 Cernan (onboard): It does look - look gray, doesn't it?

075:54:55 Stafford (onboard): Okay, 30 seconds; we'll get Delta-V, Normal.

PAO: One minute to LOI.

075:54:58 Young (onboard): Yes, and don't forget the High Bit Rate. Coming up...

075:54:59 Stafford (onboard): High Bit Rate.

[High Bite Rate on the data storage equipment recorder.]
075:55:00 Young (onboard): ...coming up whenever you go to Delta-V, Normal.

075:55:03 Stafford (onboard): Shit, baby; we have arrived - It's a big gray plaster-of-paris thing...

075:55:07 Cernan (onboard): Oh, my God, that's incredible.

075:55:08 Stafford (onboard): Okay, let's keep going; we've got to watch this bear here.

[Stafford is encouraging his crew to concentrate on their preparations for the LOI burn.]
075:55:10 Young (onboard): Put your head back in the cockpit, Gene-o.
[Despite Stafford instruction to his crew, Young is voicing his concern over Cernan's distraction by the view of the Moon outside. He is quite firmly encouraging Cernan to concentrate on the matters at hand inside the spacecraft as the crew prepare for the LOI burn.]
075:55:11 Cernan (onboard): Look at that!

075:55:12 Stafford (onboard): Let's go.

075:55:13 Cernan (onboard): Okay, I'm ready.

075:55:14 Stafford (onboard): Okay, the High Bit Rate, go ahead; hit it.

075:55:15 Cernan (onboard): High Bit Rate...

075:55:33 Stafford (onboard): Okay, 22 seconds. Standing by to push the Thrust On. 18 seconds. Get your watch; we're all set, babe...

[With the SCS in Delta-V mode, the Thrust On push button provides a logic signal which energizes the SPS relays and solenoid control valves. It remains on throughout the SPS thrusting period.]

Thrust On button P1

Thrust On push button on panel 1.

Click on above image for full panel diagram.

075:55:42 Young (onboard): All set.

075:55:43 Stafford (onboard): ...Count us down, Gene-o. Delta-V to Normal; rechecked. Everything is good. Delta...

[Stafford is repeating to himself the instruction to set the Delta-V Thrust switch A to the Normal position. See note at 075:53:28]
075:55:45 Cernan (onboard): 10 seconds.

075:55:46 Stafford (onboard): ...Okay, and get that On in 3 seconds. [Garble] Delta-V.

075:55:47 Cernan (onboard): Stand by.

075:55:48 Stafford (onboard): ...7...

075:55:49 Cernan (onboard): 5 seconds.

075:55:50 Stafford (onboard): 5, Proceed, 3, 2, 1...

[At ignition minus 5 seconds, Stafford has to command the CMC that he approves the SPS ignition on time by pressing the Proceed button on the DSKY whilst in program P40.]
PAO: 5 seconds. Ignition. Apollo 10 should be burning now. And at that time of ignition, Apollo 10 was 98.4 nautical miles [182.2 km] from the Moon, 215,847 nautical miles [399,746 km] from Earth. We have 2 clocks counting in the control room now. The top clock reading AOS CM. It reads 25 minutes, 8 seconds. That's the acquisition of signal time with a good LOI burn. The bottom clock reads 14 minutes, 24 seconds and that is the acquisition time if Apollo 10 did not perform the burn. Flight Director Chris Kraft describes the attitude in this Control Center now as anticipatory. It's very quiet in this control room right now. A few conversations going but not very many. Most controllers sitting at their consoles very quietly. The entire Apollo 10 backup crew is here in the Control Center; Gordon Cooper, Donn Eisele, and Ed Mitchell. Two CapComs; Charlie Duke and Bruce McCandless. Jack Schmitt is still here. Deke Slayton, the Director of Flight Crew Operations is here talking at the moment with Dr. Robert Gilruth, the Director of MSC. George Low, the Apollo Spacecraft Program Manager is here with Chris Kraft, the Director of Flight Operations. Lt. General Samuel Phillips, the Apollo Program Director, is seated next to them. On the other side of General Phillips is George Hage, the Mission Director. We understand that Dr. Kurt Debus, the Director of the Kennedy Space Center and Dr. von Braun, the Director of the Marshall Space Flight Center are in the viewing room. We'll try to get a list of some of the other people in the viewing room. And this is Apollo Control. Among other distinguished visitors in the viewing room are Dr. George Mueller, the Associate Administrator for Manned Space Flight, NASA; Mr. Lou Evans, the President of Grumman Aircraft Engineering Corporation, the prime contractor for the Lunar Module; and the Vice President for Space of that company, Joe Gavin. The manufacturer of the Command Module Charlie Brown is represented by William Bergen, President of the Space Division of North American Rockwell. And Rusty Schweickart who was the Lunar Module Pilot on the Apollo 9 mission is in the viewing room.

075:55:55 Cernan (onboard): Okay, we're burning; you got good valves.

075:55:57 Stafford (onboard): Okay, bank the Delta-V...

[Stafford is referring to the SPS control banks which are selected by the Delta-V Thrust switch.]
075:55:58 Cernan (onboard): You got four good valves; you got four good valves. Helium Valves are Closed, you got four good valves.
[The four valves are the SPS solenoid control valves, which control the propellant ball valves. The SPS pressurization helium valves are closed during SPS non thrusting periods, with its talkback indicator showing barber pole.]

SPS He Valve P3

SPS helium valve switches and talkback indicators on panel 3.

Click on above image for full panel diagram.

075:56:05 Stafford (onboard): Guidance looks good.

075:56:07 Cernan (onboard): Guidance looks good. Boy, it's a soft burn right now. Come on, balance up, you mother. It's 15 seconds into the burn; she ought to start balancing now. Okay, and...

[Any deviation from the nominal oxidizer to fuel ratio (1.6:1 by mass) is displayed by the Unbalance indicator in pounds. The upper half of the indicator is marked Inc and the lower half is marked Dec to identify the required change in oxidizer flow rate to correct any unbalance condition. The marked or shaded area is a normal unbalance range area.


Oxidizer Unbalance meter and Oxidizer Flow Valve switches on panel 3.

Click on above image for full panel diagram.

The crew can determine if a true unbalance of propellant remaining exists. With the PUG (Propellant Utilization and Gauging Subsystem) mode switch in Prim or Norm, the crew display percentage readouts would not indicate the same percentage value and the unbalance meter would indicate the amount of unbalance in pounds. To verify if a true unbalance condition exists, the PUG mode switch would be positioned to Aux. If the crew display percentage readouts and the unbalance meter now read similar to the readouts when in Prim, a true unbalance condition exists.

The crew display readouts and unbalance meter could not be considered accurate until the SPS engine is thrusting for at least 25 seconds. This is to allow complete propellant settling in the SPS tanks before the gauging system is within its design accuracy.

If an unbalance condition exists, which is determined from the Incr, Decr readings on the unbalance meter on panel 3, the crew use the propellant utilization valve to return the remaining propellants to a balanced condition. The propellant utilization is not powered until a Thrust On command is provided to the propellant utilization gauging control unit. The propellant utilization valve housing contains two sliding gate valves within one housing. One of the sliding gate valves is the primary, and the remaining valve is the secondary. Stops are provided within the valve housing for the full increase or decrease positions. There are separate stops for the primary and secondary sliding gate valves. The secondary propellant utilization valve has twice the travel of the primary propellant utilization valve. This is to compensate for the primary propellant utilization valve failure in any position.

The propellant utilization valve controls are located on panel 3. The Oxid Flow Prim/Sec switch, selects the primary or secondary propellant utilization valve for operation. The normal position of the Oxid Flow Valve select switch is Prim. The Oxid Flow Valve select switch will not be moved to Sec unless a problem is encountered with the primary valve. The Oxid Flow Valve Incr, Norm, Decr switch is utilized to position the selected primary or secondary propellant utilization valve. When the Oxid Flow Valve switch is in Norm and the Oxid Flow Valve select switch is in Prim, the sliding gate valves are in a nominal flow position. The upper and lower Oxid Flow Valve position indicators are gray. When the unbalance meter informs the crew of Incr, the Oxid Flow Valve switch is positioned to Incr and the Oxid Flow Valve select switch is in Prim. The primary sliding gate valve then moves to the increase flow position. The valve movement will take approximately 3.5 seconds to reach the full increase position. The upper Oxid Flow Valve position indicator would then indicate Max and the lower indicator would remain gray. The Oxid Flow Valve would then be left in the Incr oxidizer flow position. This will increase the oxidizer flow approximately 3 percent above the nominal oxidizer flow. When the unbalance meter informs the crew of approximately zero unbalance, the oxid flow valve switch is then positioned to Norm. The primary sliding gate valve would then return to the nominal flow position. The valve movement will take approximately 3.5 seconds to reach the nominal flow position. The Oxid Flow Valve upper indicator would then return to gray. The lower indicator would remain gray.

When the unbalance meter informs the crew to Decr the oxidizer flow, the Oxid Flow Valve switch is then positioned to Decr with the Oxid Flow Valve select switch in Prim. The primary sliding gate valve then moves to the decrease flow position. The valve movement will take approximately 3.5 seconds to reach the decrease flow position. This will decrease the oxidizer flow approximately 3½ percent below that of the nominal oxidizer flow. When the primary gate valve reaches the Decr position, the upper Oxid Flow Valve position indicator remains gray and the lower indicator would indicate Min. The Oxid Flow Valve would then be left in the Decr position. When the unbalance meter informs the crew of approximately zero unbalance. The Oxid Flow Valve switch is then positioned to Norm. The primary sliding gate valve would then return to the nominal flow position. The valve movement will take approximately 3.5 seconds to reach the nominal flow position. The Oxid Flow Valve upper indicator would then return to gray. The lower indicator would remain gray.

The secondary propellant utilization valve is selected by positioning the Oxid Flow Valve select switch from Prim to Sec. The Sec position would be selected in the event of a problem with the Prim. The secondary sliding gate valve would then be controlled and operated by the Oxid Flow Valve Incr. Norm, Decr switch in the same manner as the primary valve. The position indicators would then operate in the same manner as in the primary. however, now indicating the secondary valve position.]

075:56:16 Young (onboard): It's on now.

075:56:17 Cernan (onboard): ...chamber pressure's 95. Okay, all my pressures are looking good, babe.

075:56:22 Young (onboard): 75, 80, 85, 90...

[The SPS engine combustion chamber pressure is displayed as a percentage to the crew on the multi-purpose rotary SPS Pc meter on panel 1. The normal range during an SPS burn is 95 to 105%. The percentage readout correlates directly to the same measurement in psia, i.e. 98% = 98 psia. The measurement is provide by a transducer on the engine injector.]

SPS P<sub>c</sub> meter P1

SPS Pc meter on panel 1.

Click on above image for full panel diagram.

SPS P<sub>c</sub> meter

075:56:23 Cernan (onboard): Okay, we burn it for 30 [garble] on the A.
[The SPS engine has dual banks of controls and valves to provide redundancy. The burn could be made using only one bank, but the Apollo 10 mission rules set out that for long burns, the engine should be ignited using bank A only and after 30 seconds, bank B should be energized so as to provide a redundant set of controls should bank A malfunction. The banks are selected using the Delta-V Thrust A or B switch. See note at 075:53:28]
075:56:24 Young (onboard): ...we better start balancing that - the oxidizer here.

075:56:25 Stafford (onboard): Good.

075:56:27 Cernan (onboard): Okay, everything's looking good...

075:56:30 Stafford (onboard): Do you want...

075:56:31 Cernan (onboard): ...pressures are still good.

075:56:33 Stafford (onboard): Looking good at 30 seconds. EMS is agreeing with the G&N.

[The crew would be running program P40 on the CMC, which will display the remaining Delta-V in the LOI burn. The EMS Delta Velocity Indicator is set prior to ignition to the desired Delta-V of the LOI burn. It will display the remaining Delta-V as the burn proceeds. This gives a comparison to the figure provided by the CMC.]

EMS Delta-V counter

EMS Delta-V counter on panel 1.

075:56:38 Cernan (onboard): Okay, she's balancing up nicely.

075:56:40 Young (onboard): Okay, chamber pressure's 97...

[Young is noting that the SPS chamber pressure indicated on the SPS Pc meter continues to climb.]
075:56:42 Stafford (onboard): Holding steady.

075:56:43 Young (onboard): ...and holding steady, and it jumped about 4 when it turned on the second bank. Gimbal motors is Go.

[The SPS chamber pressure jumped momentarily by 4 percent when the bank B SPS controls were switched on and then returned to the previous reading of 97 percent.]
075:56:47 Cernan (onboard): Okay, four good banks, helium pressure's Go, and - fuel oxidizer pressures are Go.
[Cernan is referring to the measurements he is observing on the bank of 4 gauges displaying the SPS temperature, helium, fuel and oxidiser pressures on panel 3.]

SPS Press temp gauge P3

SPS temperature, helium, fuel and oxidiser pressure gauges on panel 3.

Click on above image for full panel diagram.

075:56:54 Stafford (onboard): Gimbal motors have settled down a little bit.
[The gimbal motors on the SPS engine have settled down now that the burn has become established, the chamber pressure has come up to its optimum value and the propellant have settled fully. The gimbals are no longer so active to maintain the spacecraft's vector.]
075:56:55 Cernan (onboard): Balancing up really nice, John. The PUGS is working after 30 seconds. I turned it on. Looking good.
[The PUGS system is not considered accurate until at least 25 seconds of the SPS burn has elapsed whilst the SPS propellants settle in their tanks. Cernan is happy that he is controlling the propellant balancing using the output from the PUG display.]
075:57:00 Young (onboard): Okay. Okay.

075:57:02 Cernan (onboard): Tank pressures are good.

075:57:03 Young (onboard): 98 psi. That's Go.

[SPS chamber pressure continues to climb slowly.]
075:57:05 Cernan (onboard): Helium pressures are good.
[This is the helium that is pressurising the tanks, forcing propellant into the engine.]
075:57:06 Young (onboard): Okay.

075:57:09 Stafford (onboard): How's the nitrogen [garble]?

075:57:10 Young (onboard): Okay, that chamber pressure's coming up; now it's 100.

075:57:13 Cernan (onboard): I'm still looking good here. I got four valves and tank pressures are Go.

[The four valves Cernan is referring to are the SPS solenoid control valves, which control the propellant ball valves.]
075:57:19 Stafford (onboard): You have 4 minutes.

075:57:20 Young (onboard): The roll is trimming out a little. How's your regulator pressure...

075:57:22 Cernan (onboard): 1 minute, 30 seconds into burn; we've got a – Regulated pressures all good.

075:57:27 Stafford (onboard): Things are looking good.

075:57:28 Cernan (onboard): Okay, John we're coming up at 01:40 at the end of mode 1.

[Abort mode 1 lasts for the first 105 seconds of the Apollo 10 LOI burn. See the details of the various LOI abort modes at 073:37:19]
075:57:31 Young (onboard): Okay.

075:57:33 Cernan (onboard): Okay, we're in no-man's land; 01:40; and everything's looking good.

075:57:36 Young (onboard): Our chamber pressure's up to 101 now.

075:57:41 Stafford (onboard): 04:14 to go.

075:57:42 Cernan (onboard): Okay, babe; let's get by 2 minutes. We're in no-man's land; everything's looking good.

[For 15 seconds on Apollo 10 they were between abort modes, hence Cernan's reference to no-man's land.]
075:57:47 Young (onboard): Alright.

075:57:50 Cernan (onboard): Everything's looking good. 01:55.

075:57:53 Stafford (onboard): Looking good.

075:57:54 Cernan (onboard): Boy, it's a nice soft burn; keep burning, baby...

075:57:55 Stafford (onboard): 2 minutes.

075:57:56 Cernan (onboard): 2 minutes.

075:57:57 Cernan (onboard): Mark. We're into mode 2. Okay, we're into mode 2.

[They are now into the mode-2 abort period. See the details of the various LOI abort modes at 073:37:19]
075:58:00 Stafford (onboard): Okay.

075:58:02 Cernan (onboard): She's going on the Increase; I'm going to balance back the other way.

075:58:07 Stafford (onboard): Okay, I'm looking at the burn and what we have to do - It'll be 50.

075:58:11 Cernan (onboard): Okay, all my pressures here are holding good, John.

075:58:14 Young (onboard): Holding good here. We're up to 102 psi – chamber pressure. That little baby's getting better and better.

075:58:20 Stafford (onboard): 18 6 [garble] go. 18 7 [garble]...

[LOI burn time in seconds.]
075:58:25 Cernan (onboard): Come on, baby. Balance back down; balance back down...

075:58:28 Young (onboard): You approaching crossover yet, Gene-o?

075:58:29 Cernan (onboard): ...balance back down - No, I'm only at 72 percent, but I can't get that son of a bitch to balance back down. Here it comes. Come on, baby.

075:58:38 Young (onboard): Don't lean on...

075:58:39 Cernan (onboard): 70 percent. Everything's looking good here.

[Propellant quantity is down to 70%. Cernan is controlling the propellant balancing. See notes on balancing at 075:56:07.]
075:58:44 Stafford (onboard): 3 minutes - to burn.

075:58:48 Stafford (onboard): If the G&N's right, we'll burn...

075:58:51 Cernan (onboard): Coming up to 3 minutes, John.

075:58:52 Stafford (onboard): 3 55 [garble].

[LOI-1 burn has 3 minutes, 55 seconds remaining.]
075:58:54 Young (onboard): [Garble]. Okay.

075:58:55 Stafford (onboard): [Garble]. 5 56.

[Stafford is making a prediction of the total SPS burn time; 5 minutes, 56 seconds.]
075:58:56 Young (onboard): Mark it, 3 minutes.

075:59:00 Cernan (onboard): Come on, baby. Get that thing going.

075:59:02 Young (onboard): Yaw's off in roll. See that?

075:59:04 Stafford (onboard): Yes, I saw that, John.

075:59:05 Young (onboard): Okay, we're up to 102 pounds now. Son of a gun's just getting better all the time.

075:59:11 Stafford (onboard): Yes.

075:59:12 Young (onboard): That's the roll thruster firing to bring it back in.

[The roll RCS thrusters are firing under command from the CMC to correct the spacecraft's attitude.]

[Young in the Apollo 10 Crew Technical Debrief described the roll transients - "It was steady, and the thing that was noted about the burn transient, as on the D mission, was that you get continued control in roll; it's up against the deadband, but it gives you a very good feeling of how the vehicle is performing".]

[The roll deadband during the LOI burn was set at ±5°]

075:59:14 Cernan (onboard): Okay, your - all your pressures are looking good right now. Except I can't get that increase now. Come on, baby. I don't want to switch to secondary valve yet, because it's not off that far.

075:59:24 Young (onboard): What secondary valve? Don't go on a backup.

[Young is encouraging Cernan not to switch to the secondary propellant utilization valve. See the notes on balancing at 075:56:07]
075:59:26 Cernan (onboard): No, no, it's still slowly in the - Everything's looking good; you're at 3 minutes and coming up on 40 seconds.

075:59:34 Stafford (onboard): Coming up - coming up to 2 minutes to go, John. It's looking good. Beautiful, baby.

075:59:38 Young (onboard): My God, there it is.

075:59:40 Stafford (onboard): Oh, you'd better believe it.

075:59:41 Cernan (onboard): There it is, is right...

075:59:42 Stafford (onboard): Strangest looking son of a bitch I've ever seen.

075:59:44 Young (onboard): Isn't that weird?

075:59:45 Stafford (onboard): Okay, let's go. 2 minutes to go. Looking good.

075:59:47 Cernan (onboard): Okay, all your valves are still good. 102.

075:59:50 Stafford (onboard): 2.

075:59:51 Cernan (onboard): 102 on the psi.

075:59:52 Stafford (onboard): I'm estimating that the G&N is going to be about...

075:59:55 Cernan (onboard): Okay, we're at crossover right now on the - on the propellants.

075:59:57 Young (onboard): Okay, and don't pay any attention to what it's...

075:59:58 Stafford (onboard): Don't worry; we're about [garble]...

[Flight Plan page 3-40.]
076:00:00 Young (onboard): 102.

076:00:01 Stafford (onboard): I'm going to estimate 5 plus; 58 for the burn.

[Based on the indicated SPS engine performance, Stafford is estimating the engine will be shut off automatically by the CMC after a burn time of 5 minutes, 58 seconds. He is making this estimation so they can calculate how long they should let the SPS engine burn beyond that time should the auto cut-off not occur and they have to manually shut it down.]
076:00:04 Young (onboard): Okay. Okay, there's 4 minutes and coming up on 15 seconds.

076:00:10 Stafford (onboard): Yes.

076:00:14 Cernan (onboard): Oh, would you believe it? There's the lunar horizon.

076:00:16 Stafford (onboard): Okay, how's the - propellant tanks are looking good.

076:00:18 Cernan (onboard): Everything's looking good, babe.

076:00:19 Young (onboard): Helium's up to 103. 104.

076:00:23 Stafford (onboard): First I've heard of a bloody engine going up...

076:00:26 Young (onboard): Okay, there's...

076:00:27 Stafford (onboard): ...[garble].

076:00:28 Young (onboard): ...[garble].

076:00:29 Stafford (onboard): Okay, we're getting down to 1 minute to go and - guidance is fantastic.

076:00:35 Young (onboard): Beautiful, just beautiful. Just beautiful.

076:00:39 Stafford (onboard): Beautiful guidance; you couldn't ask for any better.

076:00:41 Young (onboard): It's solid as a rock.

076:00:42 Cernan (onboard): Tank pressures are looking good.

076:00:43 Stafford (onboard): Okay, good. Fuel is holding good, Gene-o.

076:00:46 Cernan (onboard): Everything's looking good, babe. You're well into mode 3.

[They are now into the time period of the mode 3 abort plan. See the details of the various LOI abort modes at 073:37:19]
076:00:48 Stafford (onboard): Good, okay. Good. I'm going to say that it'll be 5:56 to get to [garble].
[Stafford is amending his estimate of the total SPS burn time to 5 minutes, 56 seconds.]
076:00:52 Young (onboard): 4 [garble] but that chamber pressure's...

076:00:55 Stafford (onboard): [Garble] that we have on [garble].

076:00:56 Cernan (onboard): Okay, there's 5 minutes, babe.

076:00:58 Stafford (onboard): I'm standing by on the valves, John.

[Stafford is preparing to set the Delta-V Thrust switches A and B to Off to shut down the SPS controlling banks A and B.]
076:01:00 Young (onboard): Okay.

076:01:01 Stafford (onboard): 49 seconds to go.

076:01:02 Young (onboard): Okay.

076:01:07 Cernan (onboard): We're pulling (laughter) 0.2 or 0.3 of a g, I can't...

076:01:10 Stafford (onboard): 40 seconds to go.

076:01:13 Young (onboard): Okay.

076:01:14 Stafford (onboard): 35.

076:01:17 Young (onboard): 5, 4...

076:01:19 Stafford (onboard): 30 seconds to go. Estimating at 5 plus 56.

[Stafford is sticking with his estimate of a total SPS burn time of 5 minutes, 56 seconds and will count down to cut-off based on this estimate.]
076:01:23 Young (onboard): Okay.

076:01:25 Cernan (onboard): Going to close this thing. Get it closed before we shut down.

076:01:30 Stafford (onboard): 20 seconds, babe.

076:01:31 Young (onboard): Okay.

076:01:32 Stafford (onboard): Stand by for the valves. 18, 17, 16, 15, 14, 13, 12, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1...

076:01:50 Stafford (onboard): Shut - SECO - valves [garble]...

[Both Delta-V Thrust switches are set to Off.]
076:01:51 Cernan (onboard): There's all four valves Closed, Helium Valves are Closed. Everything's Go.
[Cernan is confirming that the four SPS Engine Injector Valve indicators have moved to their Closed position, and he has set the Helium Valves to the Closed position.]

SPS inj vlv ind P3

SPS Engine Injector Valve indicators on panel 3.

Click on above image for full panel diagram.

076:01:54 Stafford (onboard): Gimbal Motors, Off. TVC Servo Power, Off.
[The crew is now safing the SPS engine and its associated systems.]
076:02:00 Cernan (onboard): Whew! Babe, I think we's here.

076:02:02 Stafford (onboard): Oh, you know we are.

PAO: This is Apollo Control. As Apollo 10 went behind the Moon, we were showing a distance of 256 nautical miles [474 km] from the Moon, velocity of 7,770 feet per second [2,369 m/s] and a spacecraft weight of 93,281 pounds [42,408 kg]. They were in a good Lunar Orbital Insertion burn. We should reacquire Apollo 10 in 20 minutes, 52 seconds; at an elapsed time of 76 hours, 22 minutes, 58 seconds.

076:02:03 Young (onboard): Bus Ties, Open.

076:02:04 Stafford (onboard): Bus Ties, Open.

076:02:05 Cernan (onboard): Okay, Bus Ties.

[During high power demand, supplemental power to the main DC buses can be supplied from the CM batteries A and B via the battery buses and directly from battery C. By setting the Main Bus Tie to Bat A/C, the battery A bus is connected to DC main bus A and battery C to DC main bus B. Also, setting the Main Bus Tie to Bat B/C connects battery B bus to DC main bus B and battery C to DC main bus A. During the SPS burn both switches were set as detailed above.]

Main bus ties P5

Main Bus Tie switches on panel 5.

Click on above image for full panel diagram.

076:02:07 Stafford (onboard): BMAGs, Rate 2. EMS to Standby. Okay, you want to take the readings on the...
[The EMS MODE switch is set to Stby (standby). In this position, all of the settings on the EMS Function rotary switch are inhibited except Delta-V Set, Rng Set (range) and Vo Set.]
076:02:11 Young (onboard): Minus 7 on EMS.

076:02:13 Stafford (onboard): Minus 7 (coughing).

[The EMS was counting down the velocity change (Delta-VC) as the LOI burn progressed, ready to shut down the engine when it reached zero. This should have happened at the same time the G&N system decided to do so. However, unlike the G&N system, the EMS did not take account of the SPS thrust tail-off. Minus 7.0 fps (2.1 m/s) represents how much velocity change the EMS measured after it reached zero. Some of the figure will be due to the thrust tail-off and some to the errors in MCC-H prediction of what figure Delta-VC should have been.]
076:02:14 Cernan (onboard): Okay, let me - let me read that stuff. Let me take that stuff.

076:02:17 Young (onboard): (Sigh.)

076:02:18 Cernan (onboard): What is it? Minus 7?

076:02:19 Stafford (onboard): Yes.

076:02:20 Cernan (onboard): What was the burn time, Tom?

076:02:22 Stafford (onboard): The total burn time...

076:02:23 Cernan (onboard): Yes.

076:02:24 Stafford (onboard): ...was 5 minutes and 56 seconds.

[Stafford's burn time prediction was spot on.]
076:02:29 Young (onboard): Minus 7 on EMS. I'll turn it Off.

076:02:30 Cernan (onboard): At what? Give it? What was it?

076:02:32 Stafford (onboard): Hot time: 05:56.

[Hot time = total LOI burn time.]
076:02:33 Cernan (onboard): I mean, what was the EMS?

076:02:35 Young (onboard): Okay, well, let's proceed out of here, huh?

076:02:36 Stafford (onboard): Let's proceed [garble] proceed.

076:02:37 Cernan (onboard): What was the EMS? Okay. Give me - give me those. Plus 0.1, residuals are...

076:02:44 Stafford (onboard): Zero...

076:02:45 Cernan (onboard): ...zero, minus 0.2. Zero, minus 0.2 of zero.

[A long burn with the SPS such as the LOI burn is unlikely to achieve the precise velocity changes required in the three axes as called for in the LOI PAD. Using Noun 85 whilst in program P40 on the CMC the velocity errors in the three axes are displayed as VgX, VgY, VgZ. These values represent the velocities, in fps, still to be gained and are known as residual velocities. For Apollo 10's LOI burn the residuals are VgX 0.0, VgY minus 0.2, VgZ 0.0. After many burns, these residuals would be corrected for (or nulled) but not on this occasion as they will be factored in to the second LOI burn PAD.]
076:02:49 Stafford (onboard): Okay, go to [garble].

076:02:51 Cernan (onboard): What was Delta-VC, John?

076:02:54 Young (onboard): Minus 7.

076:02:55 Cernan (onboard): Minus 7?

076:02:56 Young (onboard): Yes.

076:02:57 Cernan (onboard): Not 0.7, but 7?

076:02:58 Young (onboard): 7.

076:02:59 Stafford (onboard): 7 - 7.0.

076:03:01 Cernan (onboard): Okay.

076:03:06 Stafford (onboard): Go to wide deadband.

[With the deadband set to wide (maximum), the spacecraft can wander in attitude as much as ±5° before active steps are made to correct the drift.]
076:03:07 Young (onboard): Yes.

076:03:20 Young (onboard): We didn't use much gas on that [garble].

076:03:24 Stafford (onboard): Oh, man! Oh, man, look at those shallow craters.

076:03:28 Cernan (onboard): Holy smoley!

076:03:29 Young (onboard): Okay.

076:03:30 Cernan (onboard): I guess we has arrived.

076:03:31 Stafford (onboard): You'd better believe it.

076:03:32 Young (onboard): I'll tell you something. By God, they are craters!

076:03:34 Stafford (onboard): Yes. They sure don't look like it, but they're [garble] shit!

076:03:38 Young (onboard): Get some pictures, you guys.

076:03:39 Cernan (onboard): Yes.

076:03:40 Stafford (onboard): Here. I've got [garble].

076:03:44 Young (onboard): Okay.

076:03:45 Stafford (onboard): Put this watch up over there, [garble].

076:03:48 Young (onboard): Okay; now, let's make sure we've got everything shut off.

076:03:50 Stafford (onboard): Okay, yes.

076:03:51 Young (onboard): Gimbal Motors are Off. The Thrust chambers are Off; the Logic is Off; the TVC Servo Power's Off – You got the Bus Ties, Off, Gene?

[Young is just double-checking the checklist items that have already been carried out.]
076:03:58 Cernan (onboard): Yes, they want you to stay on High Bit Rate?
[The crew are discussing whether to leave the DSE recorder in High Bit Rate.]
076:04:01 Young (onboard): I don't - I don't know.

076:04:02 Stafford (onboard): I guess so. Let's look in the Flight Plan.

076:04:07 Cernan (onboard): What's - At - at I - we're crossing 150 at 75:53, which we already did, so - Son of a bitch - we're way over here somewhere.

[Cernan is trying to establish the longitude they are currently crossing. The Flight Plan states they should be passing 150° E at GET 075:53.]
076:04:14 Young (onboard): That's the weirdest-looking surface - there's some color in that.

076:04:17 Stafford (onboard): There's the coloring C - it's a brownish gray.

076:04:20 Young (onboard): [Garble].

076:04:23 Stafford (onboard): It's a brownish gray, old buddy.

076:04:22 Cernan (onboard): Like a big sandbox, though, isn't it?

076:04:24 Stafford (onboard): Yes.

076:04:25 Cernan (onboard): We is at the Moon, fellows! Can you believe that?

076:04:27 Stafford (onboard): Yes, I can believe it.

076:04:28 Young (onboard): It's a brownish gray.

076:04:29 Cernan (onboard): 60 miles?

076:04:30 Stafford (onboard): And I don't see a level spot in the whole thing. Yes, I guess we might be down close.

076:04:33 Young (onboard): It's fascinating...

076:04:34 Cernan (onboard): Well - what do we do now? (Laughter) Read the Flight Plan, I guess.

076:04:37 Stafford (onboard): Yes, alright. Let's get back with it. Okay; transfer Verb 66 Enter, when you finish that thing up real fast? Okay? Proceed.

[Verb 66 transfers the present CSM state vector to the LM state vector slots in the computer's erasable memory.]
076:04:43 Unidentified Crew member (onboard): (Coughing)

076:04:44 Stafford (onboard): Proceed.

076:04:47 Young (onboard): We got it.

076:04:48 Stafford (onboard): Oh, did you put a Verb 46 in after that?

[Verb 46 activates the DAP.]
076:04:50 Young (onboard): Yes, I did.

076:04:51 Stafford (onboard): You did?

076:04:52 Young (onboard): Yes. I was just - that was the second check.

076:04:54 Stafford (onboard): Okay, good. You got a Verb 66 Enter?

076:04:57 Young (onboard): Yes.

076:04:58 Stafford (onboard): Hold cut-off attitude to 76:00; we're already there. We've got the burn residuals?

076:05:02 Young (onboard): Yes. Then we got to get some other attitudes.

076:05:04 Stafford (onboard): Okay at 76:00 maneuver to roll 180; pitch is the same it's 232; and yaw [garble] three zeros. All we got to do is roll 180. Verb 21; Enter. Just use...

[The planned spacecraft attitude is detailed in Flight Plan page 3-39 attitude diagram. Verb 21 (to load a star code into register 1) is run as part of program P51 (IMU orientation determination).]
076:05:16 Young (onboard): Well, let's just roll 180, huh?

076:05:18 Stafford (onboard): Yes, [garble].

076:05:20 Young (onboard): Okay?

076:05:21 Stafford (onboard): Yes. Look. There you go. Oh, Translation Control to Lock.

[The Translation Control has a sliding switch on it with two positions, Armed or Locked. Stafford is moving this switch to the Locked position to avoid any inadvertent movement of the controller.]


Command Module Translation Control (TLC). The scale is in inches.

076:05:37 Cernan (onboard): Would you believe it? (Sigh) What about a camera? Try to figure out where the hell we are while you guys are doing that.

076:05:41 Stafford (onboard): Really, I - I don't think you can tell what we're at right now. Until we get acclimated to the thing. We're going to roll 180.

076:05:47 Young (onboard): Man, that is utterly unbelievable!

076:05:51 Cernan (onboard): Isn't that - isn't that something? When I first saw that reflecting in that LM window, I about came unglued!

076:05:56 Young (onboard): I just don't know what to think of that. That's just fantastic!

076:06:00 Cernan (onboard): I about came un - Look at this! Oh, look! Give me that camera, Tom...

076:06:03 Young (onboard): Are we at America?

[When the early Apollo flights reached the Moon's far side, the IAU (International Astronautical Union, a body tasked with giving names to bodies and places in the Solar System) had not caught up with the pace of exploration and had not yet officially named the major features around the Moon's far side. Understandably, and to help with identification, the people of Apollo applied their own names. Most of the names for small-scale features around landing sites have stuck but all those for large features were eventually replaced by the IAU according to their naming conventions.]

[What the Apollo 10 crew are calling 'America' is now known as Korolev. This massive 437-km walled plain is really a small multiring basin, having the vestiges of an inner ring visible within the main crater rim. Sergei P. Korolev (1906-1966) was the mastermind behind the early Soviet space program, being largely responsible for both the first unmanned and manned spacecraft.]

076:06:04 Stafford (onboard): You got it.

076:06:05 Young (onboard): We're at America, aren't we? Take pictures of that thing.

076:06:07 Cernan (onboard): Give me that camera.

076:06:08 Stafford (onboard): Here, take [garble].

076:06:09 Young (onboard): I - should I be using this one, I wonder?

076:06:10 Stafford (onboard): Don't get much of the horizon.

076:06:11 Young (onboard): Don't get much of the horizon.

076:06:12 Cernan (onboard): The what? Don't get much of horizon?

076:06:14 Stafford (onboard): Take the slide out.

076:06:16 Cernan (onboard): I should probably have the other lens right here.

076:06:20 Young (onboard): By golly, that's fascinating!

076:06:22 Stafford (onboard): That stuff looks gray. It was brownish gray.

076:06:24 Cernan (onboard): It was brownish gray to me.

076:06:26 Stafford (onboard): It's brownish gray.

076:06:27 Cernan (onboard): Oh! What the hell's wrong with it? What the hell is wrong with it?

076:06:30 Young (onboard): You've got to fix it. God damn it, that slide...

076:06:32 Cernan (onboard): The son-of-a-bitch camera, I took the slide out.

076:06:35 Young (onboard): It's that damn thing; you've got to wind it, remember? You got to cock the film...

076:06:38 Stafford (onboard): And it's in black and white...

076:06:39 Cernan (onboard): You wind it which way?

076:06:40 Stafford (onboard): Here. Let me show you.

076:06:42 Stafford/Young (onboard): Take that one, Gene-o.

076:06:43 Stafford (onboard): Then [garble] this one. You wired it for red.

076:06:45 Young (onboard): Okay. When do we get AOS [Acquistion Of Signal], Gene-o?

076:06:48 Cernan (onboard): At 22.

076:06:49 Stafford (onboard): [Garble] white. Okay, you're all set.

076:06:51 Young (onboard): Shoot, I want to take...

076:06:55 Stafford (onboard): Okay, we have AOS at 76:22. Okay?

076:07:04 Young (onboard): Just not much of the horizon there, Gene-o.

076:07:06 Cernan (onboard): I'm not taking any of it, because I don't see it. I got – you know, I think it looks bluish gray.

076:07:16 Young (onboard): By God, we're all satisfied it's got color in it of some kind...

076:07:18 Stafford (onboard): [Garble] color.

076:07:23 Young (onboard): [Garble] brownish to me.

076:07:24 Stafford (onboard): It's a brownish gray.

076:07:25 Young (onboard): I agree with Tom; I think it's got a little brown in it...

076:07:26 Stafford (onboard): It's brownish gray. Very little - occasional white, but mostly brownish gray. And I would say the – the gray predominates - it's 50/50. Hey, as we're coming to right-side up, it's easier to shoot, Gene-o.

076:07:41 Cernan (onboard): Okay. I think - Do we want this lens that – Look at some of those craters!

076:07:45 Young (onboard): Yes.

076:07:46 Cernan (onboard): I tell you, I'd sure like to know where we are.

076:07:48 Stafford (onboard): Well, look; get out the map. You can – you’ve been trying to work...

076:07:50 Cernan (onboard): [Garble] I got...

076:07:51 Stafford (onboard): ...to get this on...

076:07:52 Cernan (onboard): Hey, look at - look at this thing that's floating with us out this window, Tom. See it?

076:07:55 Stafford (onboard): Yes, I've seen it. It's a big bubble.

076:07:56 Cernan (onboard): A big bubble right with us.

076:07:57 Young (onboard): It's a what? A what?

076:07:58 Stafford (onboard): A bubble.

076:07:59 Young (onboard): Take a picture of that.

076:08:00 Cernan (onboard): A bubble.

076:08:01 Stafford (onboard): Well, there's a bubble from - probably from the urine dump...

076:08:04 Young (onboard): Oh.

076:08:05 Stafford (onboard): ...or something. And then there's a...

076:08:08 Cernan (onboard): I imagine people will think it's a - You want to try this?

076:08:11 Stafford (onboard): No...

076:08:12 Cernan (onboard): See if I can navigate and find out where we are.

076:08:14 Young (onboard): See what Verb 82 says, and write that down.

[Verb 82 is used as part of computer routine R30. This routine is used to provide the crew with their current orbital parameters.]
076:08:16 Young (onboard): Yes.

076:08:17 Cernan (onboard): (Coughing)

076:08:18 Young (onboard): That should be a little better this time...

076:08:20 Cernan (onboard): Let me get that in so I can put it in the postburn report...

076:08:22 Young (onboard): ...6. 169.1 by 59.6. Now, where the hell is it? 1 - 165.

[Young is struggling to find his post-burn notes of the orbit parameters displayed by the CMC. Apolune (orbit high point), 169.1 nautical miles (313.2 km); perilune (orbit low point), 59.6 nautical miles ( 110.4 km).]
076:08:34 Cernan (onboard): God, it's brown all around that crater there, I swear.

076:08:37 Young (onboard): 1.1 by 59.6.

076:08:40 Stafford (onboard): Yes.

076:08:42 Cernan (onboard): The only thing I didn't like about the whole operation is the unbalanced Mickey Mouse - I never could catch up with it.

[Cernan's Mickey Mouse comment, refers to his role during the LOI burn, of balancing the fuel to oxidiser ratio. He had found it difficult at times to bring the mix into balance. See balancing notes at 075:56:07]
076:08:47 Stafford (onboard): Making sure we got a [garble].

076:08:48 Young (onboard): Well, did you get...

076:08:49 Cernan (onboard): You see, it went unbalanced at 300, and then I put decrease, and then I get it to neutral, and then I stopped it; and then it went way up and I never could catch up with it.

[Cernan has noted that the propellants became unbalanced at 3:00 minutes into the LOI burn.]
076:08:55 Stafford (onboard): Okay, why don't we time - We've got a time hack back there, two pages back.

076:08:59 Young (onboard): Okay, the - this helium pressure went from like 98 to 100...

076:09:03 Cernan (onboard): Let me write that down there.

076:09:04 Young (onboard): ...and 3. It was doing it throughout the burn, just beautiful. And then - with a notable increase...

076:09:11 Cernan (onboard): Oh, hell there. Okay, I'll just pass [garble] all I know...

076:09:16 Stafford (onboard): [Garble]. By God, I'll get that from Jack Schmitt. And I'll clue you. 5.6 now [garble].

[Camera aperture stop setting. f:5.6.]
076:09:25 Young (onboard): [Garble]...

076:09:26 Stafford (onboard): Hey, you shooting at 5.6, Gene-o?

076:09:29 Cernan (onboard): Yes, I hope so.

076:09:30 Stafford (onboard): Well, it had about f:11 there, when it got - Okay. Well, it looks like Mount Shasta up there; something's definitely [garble] volcanism.

076:09:45 Cernan (onboard): Where?

076:09:46 Stafford (onboard): Well, I - I mean, you can definitely see that, can't you? See that white mound out there?

076:09:50 Cernan (onboard): Yes.

076:09:51 Stafford (onboard): [Garble]. That's definite volcanism [garble]...

076:09:53 Young (onboard): [Garble] and there isn't color in that; it's in black and white.

076:09:56 Cernan (onboard): It's black and (laughter) - Oh, Tom, give me that thing. Let me get this - let me get this fresh crater. Hold on here. This set? You should see this little white one down there.

076:10:11 Stafford (onboard): That's probably [garble] little white one on the peak.

076:10:14 Cernan (onboard): Can you see that? I'm looking right directly at it.

076:10:16 Young (onboard): Yes, I got it. Okay.

076:10:18 Cernan (onboard): That does look like a fresh volcanism because it's black inside.

076:10:22 Young (onboard): Yes, it's black in there.

076:10:26 Cernan (onboard): I guess when we get rolled over, we'll be better than old - This is the first time we'll be sitting upright that we know of.

076:10:31 Young (onboard): Here you are.

076:10:34 Stafford (onboard): What's this? You got the slide in?

076:10:36 Cernan (onboard): It's right in here, Tom. Right there. Look at that ridge; it sits right on the ridge, too.

076:10:46 Young (onboard): My gosh, we ain' t very high, you guys.

076:10:49 Cernan (onboard): We don't look it, do we?

076:10:50 Young (onboard): It doesn't look at all high to me (laughter).

076:10:53 Stafford (onboard): Wait until we get down to 10,000 feet.

076:10:57 Cernan (onboard): Holy smoley, down around 10 miles, you're going to...

076:11:00 Young (onboard): These mountains look like they'll reach right up here at us. I never saw anything [garble] This is a little bitty planet, for crying out loud.

076:11:04 Cernan (onboard): It sure is. It sure is.

076:11:08 Stafford (onboard): Okay, let’s go ahead. Let's get going; we've got a lot of things to do in the Flight Plan yet.

076:11:12 Young (onboard): I don't know what they all are. Where is the Flight Plan?

076:11:14 Stafford (onboard): Right here.

076:11:17 Cernan (onboard): Okay, and give me that thing, and see if I can help us find out where we are. Okay, I've got the S-band set up to...

076:11:22 Stafford (onboard): Okay, we'll take it. Let me get a time hack back here for these damn things, Gene-o. The time we started at 150 west, 75:52...

076:11:31 Cernan (onboard): I already got that on there. 75:53, the second one.

076:11:34 Stafford (onboard): Okay.

076:11:35 Cernan (onboard): I already got that. Now, where in hell are time [garble]?

076:11:44 Young (onboard): Okay, we done that part.

076:11:48 Cernan (onboard): You're still going backwards, right?

076:11:49 Stafford (onboard): Yes.

076:11:50 Young (onboard): Yes.

076:11:52 Cernan (onboard): Oh, my golly!

076:11:55 Stafford (onboard): We're still going backwards, okay. Now, it's – At 70, we initiate orb-rate - right away 76:17, orb-rate 350, ORDEAL. Let's get the ORDEAL going. Let's go to Lunar and 60 by 170 over the [garble] John. I'll get it. Let's go to Power on the Lunar, take an average [garble].

[The ORDEAL (Orbital Rate Display - Earth And Lunar) drives one or both FDAI (Flight Director/Attitude Indicator, or "8-ball") instruments to display the spacecraft's attitude relative to the ground below. It is a separate box of electronic controls which is connected by the crew for use by virtue of it being an add-on to the system as originally designed.]

[The ORDEAL has several controls:

The two FDAI switches set the relevant FDAI to Orb Rate to display the pitch attitude with respect to the local horizontal, or Intrl to display the inertial attitude (bypassing the ORDEAL)

The 3-way mode switch - Earth/Power Off/Lunar enables the ORDEAL to work in Earth or Lunar Orbit.

The Alt Set rotary switch allows the crew to dial in the orbital altitude, which determines the rotation rate at which the FDAI will be driven.

The 3-way Lighting switch controls the ORDEAL's electroluminescent panel, BRT, OFF, DIM.

The 2-way Mode-Opr/Slow or Hold/Fast and the 3-way Slew-Up or Down, switches allow the FDAI to be set to the correct initial attitude slowly (0.55 degrees/sec) or fast (10 degrees/sec). Once set using the Slew switch, the ORDEAL is set to Opr for normal operation. Hold would be used to maintain a constant ORDEAL output.]


[When the ORDEAL panel is not in use during launch and entry, it is stored in compartment U3 in the Upper Equipment Bay. When in use it is mounted above window 1 on the left side of the crew compartment. Stafford is setting the ORDEAL up for initial use in lunar orbit. He is setting the mode switch to LUNAR, and the ALT SET switch as prescribed to the 350 position.]

076:12:16 Young (onboard): Okay, I'll align the GDC to IMU.

076:12:18 Stafford (onboard): Yes, align the GDC to IMU and go to close rate. Then you want to call up Verb 82 - 83, right? I wonder what day it is?

076:12:31 Cernan (onboard): They know we're here, because they would have acquired us at 12. You want me to take something off your hands, Tom?

076:12:43 Stafford (onboard): The stuff get your DAP at 315 [garble] 214. You want me to get it, John?

076:12:50 Young (onboard): Go ahead. You want me to get it?

076:12:56 Cernan (onboard): Yes, the only damn thing I didn't like about that engine was the way it...

076:13:08 Stafford (onboard): It looks like we've got some pretty phenomenal hardware.

076:13:12 Cernan (onboard): God dang, that thing looks [garble].

076:13:14 Young (onboard): It's smooth as silk.

076:13:17 Cernan (onboard): I wonder what our nominal percentage is down there on the [garble].

076:13:21 Young (onboard): Enough to [garble] you back.

076:13:23 Cernan (onboard): I've got 39 percent.

[The propellant quantities were recorded at LOI cut-off for Cernan to read to MCC-H as part of the burn status report. The figures recorded were fuel 37.7 percent, oxidizer 39.5 percent. MCC-H need to know this to calculate the spacecraft weight and assess the propellant margins for the remainder of the mission.]
076:13:24 Young (onboard): That’s alright.

076:13:25 Cernan (onboard): I thought we were looking at 47 percent in the sims all the time. We've got another burn to make, yet.

076:13:32 Stafford (onboard): Yes. 40 percent.

076:13:38 Cernan (onboard): I thought we were used to looking at 47 percent?

076:13:42 Stafford (onboard): Okay, John, we got to go through - We're coming along like this. Okay, we have a [garble]; right, babe?

076:13:50 Young (onboard): Yes.

076:13:51 Stafford (onboard): Okay. Pitch down to 315 ORDEAL.

076:13:57 Young (onboard): Okay. But that's all slipped 11 minutes because of this time lag.

076:14:01 Stafford (onboard): Yes. That's 76:27. 13 minutes [garble].

076:14:08 Cernan (onboard): I'm on the middle of the [garble].

076:14:15 Unidentified Crew member (onboard): (Sigh)

076:14:21 Young (onboard): Pitch down to where? Okay, that's...

076:14:23 Cernan (onboard): 70 degrees.

076:14:36 Young (onboard): Okay, what am I pitching to?

076:14:38 Stafford (onboard): We need to pitch down to 315 inersh [inertial] for ORDEAL.

[The Flight Plan dictates that the crew should pitch down the combined spacecraft to 315° inertial and then set the ORDEAL to orb-rate at GET 076:17 plus the 11-minute slippage in the schedule mentioned by Young, i.e. GET 076:27]
076:14:44 Young (onboard): [Garble] inertial [garble].

076:14:47 Stafford (onboard): [Garble] need to pitch down.

076:14:50 Young (onboard): Okay.

076:15:05 Cernan (onboard): Got the right what?

076:15:08 Stafford (onboard): So we're going to be upside down coming around the...

076:15:10 Cernan (onboard): Disagrees - This is 37 percent at this temperature and - and pressure, so the helium pressure in the...

076:15:17 Stafford (onboard): So, we’ve rolled 180, right?

076:15:18 Young (onboard): Yes.

076:15:19 Stafford (onboard): Then we will swing down through the straight vertical; right, babe?

076:15:23 Cernan (onboard): Yes.

076:15:24 Stafford (onboard): Then we'll come over like that.

076:15:25 Cernan (onboard): Yes.

076:15:26 Stafford (onboard): Until we come into that [garble].

076:15:27 Cernan (onboard): Yes.

076:15:28 Stafford (onboard): Alright?

076:15:29 Cernan (onboard): Yes.

076:15:30 Young (onboard): Get some pictures of this, while we're pitching over; we'll probably never do this again.

076:15:33 Cernan (onboard): Yes, okay. Want to try that other lens or do you want to use this one entirely?

076:15:42 Young (onboard): Oh, boy!

076:15:43 Stafford (onboard): Black skies - Let's see, and we'll acquire at 20 minutes.

076:15:49 Young (onboard): It's the weirdest thing I ever saw in my life. This is worth the price, boy.

076:16:07 Cernan (onboard): Isn't it? I'll tell you - 60 miles looks like you're awful close to me.

076:16:15 Stafford (onboard): Do you recognize any stuff I got you?

076:16:17 Young (onboard): Yes. There's the Tallahatchie Bridge.

076:16:21 Cernan (onboard): Did you find it?

076:16:22 Young (onboard): Yes. That's my big basin. It is a big basin! Look at those sides!

076:16:28 Cernan (onboard): Where you looking, on the...

076:16:29 Young (onboard): Right up there.

076:16:30 Stafford (onboard): Oh, that whole thing?

076:16:31 Young (onboard): Yes, that whole great big thing.

076:16:33 Cernan (onboard): What latitude is that at, babe?

076:16:35 Young (onboard): I don't know; I have no idea where we're at.

076:16:39 Cernan (onboard): I should have - I - I should get my lunar – lunar chart. I've got it marked a little bit more. This is - this is - this is where the target of opportunity.

076:16:47 Young (onboard): When we have to be there?

076:16:53 Cernan (onboard): Would you believe where we are, guys?

076:16:54 Stafford (onboard): Huh? Yes, [garble] at.

076:16:56 Cernan (onboard): Would you believe where the hell we are?

076:16:58 Stafford (onboard): We've got a lot of work to do, too.

076:17:00 Cernan (onboard): I agree with you.

076:17:03 Stafford (onboard): Old Jack will flip just over that one volcano.

[Jack is scientist-astronaut, Harrison (Jack) Schmitt who, as a field geologist, helped train the crews in lunar geology.]
076:17:07 Cernan (onboard): That had to be a...

076:17:08 Stafford (onboard): Oh, yes. You could see the flows coming out of the top, and [garble]...

076:17:10 Cernan (onboard): Tom, get that one right there. It was sure black, wasn't it? We're going backwards. Let me see what the hell we're looking at? I wish...

076:17:18 Young (onboard): At least take some of that in color, so it shows up in color.

076:17:21 Cernan (onboard): Yes.

076:17:22 Young (onboard): That what-you-call-it.

076:17:24 Cernan (onboard): We come back around just the same.

076:17:34 Stafford (onboard): We need that 250?

076:17:39 Young (onboard): How's the water boiler doing there, Gene-o, babe?

076:17:43 Cernan (onboard): The water boiler's not boiling yet, because we still got good temperatures.

[Coolant in the primary loop absorbs heat from the CM and is transported to the radiators in the SM where a portion of this heat is rejected to space. When the temperature of the coolant from the SM radiators entering the evaporator (water boiler) rises to 48.0 to 50.5° F, the radiators are not rejecting enough heat to space and the evaporator mode of cooling is initiated to supplement the cooling. The glycol temperature control (Glycol Evap-Steam Press switch, Auto position on panel 2) opens the steam pressure valve allowing the water in the evaporator wicks to evaporate, using some of the heat contained in the coolant for the heat of vaporization.]

Glyc Evap Steam Pres P2

Glycol Evap-Steam Press switch on panel 2.

Click on above image for full panel diagram.

076:17:46 Stafford (onboard): Wonder what the temperatures are. Hey, there's another little one for Jack to look at. We're going to keep him busy for years.

076:17:52 Cernan (onboard): Oh, give me - give me this one. This has got a - this has got a raw - it looks like a rocky basin in it. On this crater here, Tom. Where is 315 ORDEAL, Tom?

076:18:02 Stafford (onboard): Let me check it. Right around here.

076:18:04 Young (onboard): We should be up to 70 - 3, Enter. You got that set up on ORDEAL?

076:18:13 Stafford (onboard): Yes.

076:18:14 Young (onboard): Why's this one here doing it, too?

076:18:16 Stafford (onboard): Number 2's Inertial; Power's - Auto; is EMS, Off? EMS - I mean ORDEAL? I got the power to it – in Lunar.

[Stafford is setting up the ORDEAL to drive FDAI number 2.]
076:18:27 Cernan (onboard): Why, those sides don't look - look rocky, you can see the bottom of that.

076:18:31 Stafford (onboard): It could be.

076:18:34 Young (onboard): Hey, what's going on there?

076:18:36 Stafford/Cernan (onboard): 263.

076:18:39 Stafford (onboard): You see Inertial is about equal to orb-rate there, babe.

076:18:43 Cernan (onboard): I'm coming backwards, so this stuff's got to be...

076:18:46 Stafford (onboard): That's right. Look at...

076:18:47 Cernan (onboard): ...over here.

076:18:48 Stafford (onboard): Okay.

076:18:49 Cernan (onboard): Okay?

076:18:50 Stafford (onboard): Yes.

076:18:51 Young (onboard): That had me a little worried.

076:18:52 Stafford (onboard): Yes, I understand. You guys - You see, we're going to be going upside down; we're now going straight down over the subsolar point.

076:19:01 Cernan (onboard): We certainly in hell ought to be able to pick out - Tom, you know that lunar map we got in that case? If you could reach up and grab that for me, that's a - then we'd each have one, and that's - our LM lunar map. I don't mean our strip chart, but I mean the...

076:19:12 Young (onboard): Give me - give me - give me a - give me a – give me a - a thing.

076:19:16 Cernan (onboard): That?

076:19:17 Stafford (onboard): The camera, Go.

076:19:20 Cernan (onboard): Then - then I could follow that other chart which I've got marked a lot better. I'd like to find Neper when we come around on...

076:19:25 Young (onboard): I'll get it, Tom. Where is that thing? In here somewhere?

076:19:27 Stafford (onboard): Yes, it's right in there. I want to see this one.

076:19:40 Young (onboard): That's black...

076:19:41 Stafford (onboard): There's stuff in there.

076:19:42 Cernan (onboard): That's black stuff, I can see it from here.

076:19:43 Young (onboard): That black...

076:19:45 Stafford (onboard): I've got another one - Hold it, John. I got a good one for Gene - Hold that. Yes, it's black as hell in some of that stuff.

076:20:06 Cernan (onboard): Ever see anything like this in your life?

076:20:08 Young (onboard): (Laughter) Obviously not!

076:20:11 Stafford (onboard): We're coming up to the subsolar point. Okay.

076:20:17 Cernan (onboard): Okay.

076:20:18 Young (onboard): That damn thing right there is nothing but a big hill that it looks like damn...

076:20:24 Stafford (onboard): Oh, look at that!

076:20:25 Young (onboard): ...it looks like one of the volcanoes in Arizona!

076:20:26 Stafford (onboard): That one over there.

076:20:28 Cernan (onboard): There's another fresh one, Tom. Let me get this fresh one over here with this...

076:20:30 Stafford (onboard): Yes, I've got one now.

076:20:33 Young (onboard): Watch for the horizon, babe.

076:20:34 Stafford (onboard): I don't even have the horizon...

076:20:35 Cernan (onboard): What happens if you get the horizon in?

076:20:37 Young (onboard): They take off points.

076:20:38 Cernan (onboard): Well, here's a rim crater on a rim crater. This is the one I want to track, yes.

076:20:45 Young (onboard): When does Houston supposed to come into view?

076:20:47 Stafford (onboard): Oh, look at that! What's that big crater over there?

076:20:49 Young (onboard): Well, when's AOS, you guys? (Laughter)

076:20:51 Stafford/Cernan (onboard): At 22.

076:20:52 Stafford (onboard): I think the best thing to say - [garble] Houston, tell the Earth we have arrived. Don't go into the rest of it.

076:21:02 Cernan (onboard): Here, you want this? I'm going to try and find out - We're at the subsolar point. God dang, you can't really see much! Look at! Get that one straight down, Tom, at subsolar. Can you see that little white one?

076:21:11 Stafford (onboard): I've got it.

076:21:14 Cernan (onboard): John, where would you say subsolar is on there? In longitude?

076:21:19 Young (onboard): Babe, now, don't - don't be asking me things like that, I can't - -

076:21:22 Cernan (onboard): It must be about 90 degrees, huh?

076:21:24 Stafford (onboard): Yes. What do we have - We're in PGNS to reacquire?

[Verb 64 starts the S-Band antenna routine R05. This routine computes and displays the yaw and pitch gimbal angles to point the antenna at the centre of the Earth. The crew set the angles accordingly, having taken into account whether these angles and the present spacecraft attitude, give an unobstructed line of sight view of the Earth. If they are in the attitude dictated in the Flight Plan they should have no issue with the LM obstructing the antenna's view of Earth.]
076:21:30 Cernan (onboard): Okay.

076:21:31 Stafford (onboard): Let's stand by to give them the burn (report). And also, to tell them that we have arrived.

076:21:37 Cernan (onboard): Where's the Flight Plan, so I can give them all that jazz? You say when. Give me the Flight Plan, John. You got it in here? You keep the nav, I'll take the flight.

076:21:46 Stafford (onboard): Okay, you can stop them pretty soon, John.

076:21:48 Young (onboard): Okay.

076:21:50 Stafford (onboard): Keep it upside down. And we should be going right down the Apollo Zone.

076:21:53 Young (onboard): Okay.

076:21:55 Stafford (onboard): Okay.

076:21:56 Cernan (onboard): We ought to be looking coming - We're still going backwards.

076:21:58 Young (onboard): You got your tick-tock going there? Do you know what time it is from when we started 150 west?

076:22:05 Cernan (onboard): No, I didn't time it, babe, but - I know the time. I know that the time's on the chart at 53 - is at 75:53. I marked it on there.

076:22:15 Stafford (onboard): 75:53; and at 23, it will be 30 minutes after that, right?

076:22:20 Cernan (onboard): Yes.

076:22:21 Stafford (onboard): Where do we start? There's 10 minutes, 20 minutes; okay, here's where we should be coming up to right now. 30 minutes, right here. Okay. Of course, we are coming - we're upside down, right? Going forwards.

076:22:34 Young (onboard): Yes. Look at that planet, look at that thing there?

076:22:36 Cernan (onboard): Yes.

076:22:38 Young (onboard): Hey, that's something isn’t it?

076:22:39 Stafford (onboard): Here's another volcano for - for Jack to look at. There's no doubt that there's a...

076:22:43 Cernan (onboard): There's two of them. See them together?

076:22:44 Stafford (onboard): We got...

076:22:45 Young (onboard): Oh, no, that doesn't - that's not - that little white one, Tom?

076:22:49 Stafford (onboard): Yes, I was wondering...

076:22:50 Cernan (onboard): That - that with all those rays; that's got to be an impact crater or something like that, I'll bet.

076:22:52 Stafford (onboard): But why is it going up high?

076:22:54 Young (onboard): Well, I can't tell that it is, looking down at the subsolar.

076:23:00 Stafford (onboard): Okay, stop it, José.

076:23:02 Young (onboard): Yes. We're stopped.

076:23:04 Cernan (onboard): Hey, John? You ought to be able to see a big, big Neper on your left somewhere.

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