The Apollo 10 combined CSM/LM spacecraft has nearly completed its journey out to the Moon. The precision of the TLI manoeuvre 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 manoeuvre had been made. Lessons learnt from the Apollo 8 mission would be factored into the Apollo 10 LOI manoeuvre 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 manoeuvre 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 manoeuvre 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 in this diagram, they are for the spacecraft on the first and second lunar orbits. Eleven minutes must be added to these times to allow for the slightly delayed lunar arrival.
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.
The 210-foot [64-metre] communications dish at Goldstone, California - Photo by Bill Wood via honeysucklecreek.net
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.]
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.]
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.
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.]
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.
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.
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.]
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.]
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.
072:47:28 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.
072:47:53 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.]
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.
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.
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.
High Gain Antenna Beamwidth switch - Panel 2.
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.
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?
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.
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 water flow 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.
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.
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.
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 apocynthion over the near side. This high apocynthion is to protect against an unintended overburn which could otherwise 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 centre-of-mass 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 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 purpose of this is to allow the 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 in a particular way, 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.
GDC Align angles: The align angles are roll, 241°; pitch, 240°; yaw, 13°.
Additional notes for the PAD mention that since the SPS propellant tanks are full, there is no need for an ullage burn to settle their contents. Also, the LM's mass is 30,727 pounds (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 worst 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 manoeuvre 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 manoeuvre 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 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 Two 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 manoeuvre 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 manoeuvre capability. More specifically, serious SPS problems are as follows:
Sustained pressure decay in either fuel or oxidizer tank.
Thrust chamber pressure lower than 70 psi.
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 manoeuvre (approximately 3,000 fps) as soon as possible to ensure lunar sphere escape is the major justification for a 15-minute abort manoeuvre.
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.
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.
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.
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.
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.
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.
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.
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.
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.]
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 Down Voice Backup & Tape Recorder switches - Panel 3.
074:46:10 Cernan: Roger, Charlie. Do you want those now?
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.
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.]
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.
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.
The backup Command Module Pilot Donn Eisele has joined the rest of the backup crew here in the Control Room.
Apollo 10 is 3,012 miles [5,578 km] from the Moon. Velocity; 5,201 feet per second [1,585 m/s].
The view of Earth from Apollo 10 at 075:00:00
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.
075:09:15 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 manoeuvre. 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 manoeuvre and to manoeuvre the spacecraft to this attitude. To control the GNCS during the countdown, ignition, thrusting and thrust termination of a GNCS controlled SPS manoeuvre.
075:09:24 Duke: Roger, 10. We copy. We'll be watching.
075:09:27 Cernan: Okay, Charlie.
Very long comm break.
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.
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.
075:30:10 Stafford: Okay. And we know what that is. That is due to the conic integration.
075:30:16 Duke: Roger.
Long comm break.
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 inches/sec (37.5 cm/sec).
PCM Bit Rate switch - Panel 3.
075:36:17 Duke: Roger.
Comm break.
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.
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.
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.
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.
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.
