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Day 6 part 28: Snoopy and fuel cells cause concern Journal Home Page Day 7 part 30: The Tom, John and Gene evening show

Apollo 10

Day 6 part 29: Going back to Houston

Corrected Transcript and Commentary Copyright © 2017 by David Woods, Robin Wheeler and Ian Roberts. All rights reserved.

Last update: 2019-03-18

Rev 31 spacrecraft attitude diagram

Planned spacecraft attitudes during rev 31.

(Click on above diagram for larger image.)

[135:13:-- Begin lunar Rev-31]

Flight plan

[No DSEA recording available. Photography of targets of opportunity continues whilst the spacecraft is over the far side of the Moon.]

Strip photography begins at 90° East and continues to the terminator. The spacecraft is yawed 20° off vertical at 85° East to center on Censorinus (32° East) and its approach path in the strip photography, and then maneuvered back to vertical at 30° East to center on landing site 3 (1.4° West) and its approach path in the photo strip.]

Air-to-ground audio

135:54:25 PAO: This is Apollo Control at 135 hours, 56 minutes. We're less than one minute now from acquisition of Apollo 10. The spacecraft now in its 31st revolution of the Moon. This will be the last full revolution prior to Trans-Earth Injection beginning the trip back to Earth. During this upcoming revolution the crew will be involved in getting the spacecraft and the guidance system configured for the Trans-Earth Injection maneuver. And we'll be passing up the PAD information for that burn. We should have acquisition now. We show that we have data from the spacecraft. We'll stand by for voice communication.

135:56:57 Engle: Apollo 10, This is Houston.

135:57:05 Young: Go ahead. Over.

135:57:07 Engle: Roger, 10. I've got a bunch of updates for you. First off, though, I would like to have you turn on your H2 purge line heater, and we'd like to have P00 and Accept on the computer.

135:57:22 Stafford: You've got it.

[The H2 Purge Line Heater switch on panel 3 is placed in the On position. This enables the H2 purge line to be heated to prevent freezing during a purge.]

135:57:28 Cernan: What kind of updates, Joe?

135:57:30 Engle: OK. I've got a maneuver PAD update and, Gene-o, this is for TEI-31. There are six items that have changed that we have different numbers for. Would you like for me to just call up those changes or do you want me to read the whole PAD?

135:57:46 Cernan: Why don't you call up the changes and then I'll read back to you the whole PAD?

135:57:50 Engle: That'll be great. And let me know when you're ready to copy.

135:57:55 Cernan: [Garble] I'm ready, but give me a lot of time between each change.

135:58:00 Engle: I sure will. Understand. OK. Then on your maneuver PAD, this is for TEI-31 under Noun 33, the time is - on seconds - is 28.21. Okay, for Noun 81.

135:58:26 Cernan: Go ahead.

135:58:27 Engle: Roger. Noun 81: Plus 36252, plus 0...

135:58:41 Cernan: No.

135:58:43 Engle: OK. Delta-VY is plus 00400, and Delta-VZ is plus 01880. OK. Your Delta-VT is 36303, and Delta-VC is 36077. And that concludes all the changes. I'll stand by for your readback, Gene.

135:59:44 Cernan: OK, Joe. I'm going to read back the whole PAD to you.

135:59:48 Engle: Roger.

135:59:50 Cernan: TEI-31, SPS/G&N: 36685; minus 0.62, plus 0.89; 137:36:28.21, Noun 81 is plus 36252, plus 00400, plus 1880 - correction, - that's plus 01880. Roll is 181, pitch is 051, yaw is 002; apogee is NA, perigee is plus 0021.2; 36303, 2:41, 36077; 16, 146.4, 29.4. Noun 61 is minus 15.08, minus 165.00; 1203.8, 36394, 191:50:43. Deneb, 43, and Vega, 36, are the set stars. Roll is 241, pitch is 240, yaw is 013. We're going to be two-jets for 14 seconds using quads Bravo and Delta. The horizon is on the 6-degree window mark at TIG minus 1 minute. The sextant star is not available until 137:06:00. The Sun is not visible until after TIG and the horizon is lit. Over.

[The slightly revised TEI-31 PAD is interpreted as follows:
Purpose: This PAD will be used for TEI-31 Return-to-Earth burn.
Systems: The burn would be made using the SPS (Service Propulsion System) engine under the control of the Guidance and Navigation system.
CSM Weight (Noun 47): 36,685 pounds (16,640 kg).
Pitch and yaw trim (Noun 48): -0.62° and +0.89°.
Time of ignition, TIG (Noun 33): 137 hours, 36 minutes, 28.21 seconds.
Change in velocity (Noun 81), fps (m/s): x, +3,625.2 (+1,105.0); y, +40.0 (+12.2); z, +188.0 (+57.3). These velocities are expressed with respect to the Local Vertical/Local Horizontal frame of reference of the Moon.
Spacecraft attitude: Roll, 181°; Pitch, 51°; Yaw, 2°. The desired spacecraft attitude is measured relative to the alignment of the guidance platform which itself has been aligned to the lunar lift-off REFSMMAT.
HA, expected apogee of resulting orbit (Noun 44): Not applicable. The spacecraft will be on a trajectory coming from the Moon so any apogee figure would be meaningless.
HP, expected perigee of resulting orbit (Noun 44): +21.2 nautical miles (+39.3 km). The perigee distance is so low, it intersects the Earth's atmosphere. In other words, the spacecraft will re-enter.
Delta-VT: 3,630.3 fps (1,106.5 m/s). This is the total change in velocity the spacecraft would experience. (It is a vector sum of the three components given above.)
Burn duration or burn time: 2 minutes, 41 seconds.
Delta-VC: 3,607.7 fps (1,099.6 m/s). The crew enter this figure into their EMS Delta-V counter display. The EMS can shut down the engine using this data if the G&N system fails to do so. Its value is lower to allow for the extra thrust imparted by the engine after shutdown, a quantity allowed for the the G&N software but not by the EMS.
Sextant star: Star 16 (Procyon, Alpha Canis Minoris) visible in sextant when shaft and trunnion angles are 146.4° and 29.4° respectively. This is part of an attitude check.
The next three items are not applicable because the COAS will not have a clear view to the stars.
The next five parameters all relate to re-entry, during which an important milestone is "Entry Interface," defined as being 400,000 feet (121.92 km) altitude. In this context, a more important milestone is when atmospheric drag on the spacecraft imparts a deceleration of 0.05 g.
Expected splashdown point (Noun 61): 15.08° south, 165.00° west; in the mid-Pacific.
Range to go at the 0.05 g event: 1,203.8 nautical miles. To set up their EMS (Entry Monitor System) before re-entry, the crew need to know the expected distance the CM would travel from the 0.05 g event to landing. This figure will be decremented by the EMS based on signals from its own accelerometer.
Expected velocity at the 0.05 g event: 36,394 fps. This is another entry for the EMS. It is entered into the unit's Delta-V counter and will be decremented based on signals from its own accelerometer.
Predicted GET of 0.05 g event: 191 hours, 50 minutes and 43 seconds GET.
GDC Align stars: Stars to be used for GDC Align purposes are Deneb and Vega. The align angles are roll, 241°; pitch, 240°; yaw, 13°.
The ullage burn to settle the contents of the propellant tanks is to fire two RCS (Reaction Control System) quads (B&D) for 14 seconds.
Other notes include the fact that at the correct attitude for the burn and one minute to ignition, they should expect the Moon's horizon to line up with the 6° mark on the left rendezvous window; and the sextant star does not rise above the local horizon until after 137:06:00 GET.]

Flight plan

136:02:02 Engle: Good readback, Gene. That's all correct.

136:02:20 Engle: OK. Apollo 10, Houston. We'd like for you to put fuel cell 1 back on Main A and B, please.

136:02:28 Cernan: OK. Fuel cell 1 is coming on; main A and then main B.

[The ailing fuel cell 1 is being brought back on line for a short period to provide a degree of redundancy during the upcoming TEI burn, just in case fuel cell 2 or 3 should encounter a serious problem during the maneuver. It will be taken off line as soon as the spacecraft regains communication with MCC-H following the maneuver. It can then be brought back on line if required during mid-course corrections or during the period immediately before SM jettison.]

136:02:32 Engle: OK. And I’ve got a TEI-32 maneuver PAD for you, Gene. Preliminary.

136:02:48 Cernan: Stand by.

136:03:26 Cernan: Houston, it should be on the line right now. It's carrying not quite its share of the load. When I put it on, I got the fuel cell bus disconnect, reconnected, and it stayed connected, and the same thing on bus B. It looks like it's warming up slowly.

[The Fuel Cell Bus Disconnect caution and warning light on panel 2 illuminates momentarily when any of the fuel cells are connected to DC Main Bus A or B or both buses. The fuel cells are connected to the buses by moving the Fuel Cell bus selection switch to MNA & MNB momentarily. The FC1 MNA and FC1 MNB talkbacks on panel 3 will go to gray, indicating the fuel cell is connected to each of the buses.]

FC BUS DISC c&w light P1

Fuel Cell Bus Disconnect caution and warning light on panel 2.

(Click on the above diagram for a larger version.)

FC bus connection switches P3

Fuel Cell to buses connection switches (6), with associated talkback indicators on panel 3.

(Click on the above diagram for a larger version.)

136:03:45 Engle: OK, 10. We copy all that, and it looks ok down here.

136:03:53 Cernan: OK. And you want to give me a TEI what? 32?

136:04:02 Engle: Affirmative. 32.

136:04:08 Cernan: Go ahead.

136:04:12 Engle: OK. And prior to this PAD, 10, you can go to Block on your computer. You can have it back, now. And coming up with TEI-32, SPS/G&N: your first entry is Noun 33, 139:36:25.14; plus 3757.3, plus 0029.2, plus 0034.1. Pitch is minus 050. All else is NA. Ullage will be two jets for 14 seconds. That concludes, and I'll stand by for the readback.

136:05:18 Cernan: OK. TEI-32 and SPS/G&N: 139:36:25.14; plus 3757.3, plus 0029.2, plus 0034.1. Pitch is minus 050. Two jets for 14 seconds.

[Interpretation of this preliminary PAD:
Purpose: This PAD will be used for TEI-32 Return-to-Earth burn.
Systems: The burn would be made using the SPS (Service Propulsion System) engine under the control of the Guidance and Navigation system.
Time of ignition, TIG (Noun 33): 139 hours, 36 minutes, 25.14 seconds.
Change in velocity (Noun 81), fps (m/s): x, +3,757.3 (+1,145.2); y, +29.2 (+8.9); z, + 34.1 (+10.4). These velocities are expressed with respect to the Local Vertical/Local Horizontal frame of reference of the Moon.
Spacecraft attitude: Roll, 181°; Pitch, 50°; Yaw, 2°. The desired spacecraft attitude is measured relative to the alignment of the guidance platform.
The ullage burn to settle the contents of the propellant tanks is to fire two RCS (Reaction Control System) jets for 14 seconds.
This is a preliminary PAD should the TEI burn not occur at the end of revolution 31 and in case communications are not possible with MCC-H.]

136:05:37 Engle: Readback correct, Gene-o. OK. I've got one more...

136:05:43 Stafford: OK, Houston. While we're taking this strip photography, we're going...

136:05:55 Cernan: Go ahead.

136:05:57 Engle: OK. I've got one more TEI map update, and I'm sorry to cut you out, Tom. Press on with what you were going to say.

136:06:05 Cernan: [Garble] on the map update a minute ago.

136:06:07 Stafford: You didn't send us the maneuver load, did you? And don't worry about the map update.

[Stafford is not interested in the next map update as they will be leaving lunar orbit.]

136:06:14 Engle: OK. Roger that.

136:06:33 Engle: 10, this is Houston. We sent up a state vector and a target load, external Delta-V.

[The upload to the CMC from MCC-H updated the current onboard state vector and the targeting parameters include time of ignition (TIG) and impulsive Delta-V along CSM local vertical axes at TIG.]

136:06:42 Cernan: Yes. We got it.

136:06:43 Engle: Roger.

136:07:01 Engle: Apollo 10, Houston. Gene-o, did you notice about the same kind of excursions on your temperature on that fuel cell on this time on the back side?

136:07:13 Cernan: All the way, Joe, exactly as it was the previous time, only we never did get the Master Alarm, this time. And when we came out in the sunlight, she seemed to slow down. And it's ok now. We also found something; it was this light oscillation in the O2 needle on both 2 and 3, but it's gone now, too.

136:07:35 Engle: OK. We copy that. And that's just on the dark side of the Moon. Is that affirmative?

136:07:43 Cernan: It occurs after we go into darkness about 15 minutes. And then apparently very shortly after we came out of sunrise - in the sunrise, it starts - it starts damping out.

136:07:54 Engle: OK. Understand.

136:08:32 Engle: 10, this is Houston. What are you showing for yaw now?

136:08:40 Stafford: Roger. We're making this in a different attitude than what was called up to us here. We only have just a couple of film shots left here. Over.

[MCC-H have noticed that Stafford has maneuvered the CSM to a different attitude to the one called for by MCC-H in recent updates. He explains that this is to capture a few more targets of opportunity on the sparse amount of film they had left. The attitude change is only temporary, Stafford will soon return to the prescribed values.]

136:08:48 Engle: Mighty fine, Tom. Thank you.

136:08:53 Stafford: Don't worry about it. We've already got a lot of pictures of this - on this site.

[Stafford is referring to Censorinus.]

136:08:59 Engle: Roger. Understand.

136:09:01 Stafford: Tell Jack to have a cup of coffee and just relax.

[Stafford is referring to geologist-astronaut Jack Schmitt.]

136:09:04 Engle: (Laughter) OK, Tom.

136:09:09 Stafford: We got more pictures of Censorinus than you can shake a stick at.

136:09:12 Engle: OK.

136:09:24 Young: In fact, I'll be surprised if there's anything left to take a picture of up here much.

136:09:29 Engle: Jack says that that's a highland dike, John.

136:09:48 Cernan: You got me there, Joe.

136:10:03 Engle: OK, 10. This is Houston. In your Flight Plan, when you go to your TEI attitude, we're going to recommend Omni Delta. Omni Delta.

[When the crew maneuver the CSM to the TEI attitude in preparation for the burn, they will no longer be able to point the high-gain antenna towards Earth. MCC-H is therefore giving them guidance on the most favorable Omni antenna to select in the new attitude.]

136:10:15 Stafford: Roger. Omni Delta for our attitude there at a pitch of 052.

136:10:20 Engle: Affirmative.

136:10:33 Stafford: OK. As soon as we get into that attitude, I'm going to turn all Auto RCS thrusters on. Over.

136:10:41 Engle: OK. Fine, Tom. And for your info, we'll have LOS this pass at 137:07:53 and AOS with your TEI will be at 137:45:26. And, with no TEI, we'll get you - We won't get you this. But, for your info, it's going to be at 137:54:03.

136:11:12 Stafford: OK. And where is LOS again?

136:11:15 Engle: 137:07:53.

136:11:50 Cernan: I like your "atta boy" attitude, Joe. We'll see you at 45:26, huh?

136:11:58 Engle: Roger that.

136:12:11 Stafford: And again, just over this maria area here, this area is definitely a brownish tan. And up there in the highlands, it is a light tan and the new craters look like - more like gypsum colors - been around an gypsum mine. Over.

136:12:30 Engle: OK. We copy that, Tom. Thank you.

136:12:49 Young: Anyway, that tube ought to give the true pictures, whatever it is. True colors.

136:12:55 Engle: Yes. The colors we've been seeing on that are just exactly as you've been describing them all the way through - all the way from the whites to the browns down to the blacks. And when you talk about the brownish grays and deep grays and blacks, why, it looks just like that on the tube.

136:13:11 Stafford: Roger. Good show. One quick thing after TEI and we give you all the report, we're going to turn away so we can just look back at it and take some motion pictures of the Moon. See, then will be kind of relax time, and we'll flip the tube on for you and we'll see what it looks like in total color going away. But I hear we're going to be through Honeysuckle. Is that right? Over.

136:13:32 Engle: That's affirmative. We're coming through Honeysuckle, Tom, and I guess they're going to be watching you coast to coast for the first program of that type over there, too.

136:13:44 Stafford: OK. Have they got color over there? I say there, down below.

136:13:54 Engle: I guess they're black and white over there, Tom.

136:14:00 Stafford: OK. What I was really getting at, the station can receive it and everything from the color camera?

136:14:06 Engle: Roger that.

136:14:10 Stafford: OK. Good show.

Air-to-ground audio

136:15:46 Stafford: OK, Houston; Apollo 10. We're coming up on the highland areas. And again, in our general observation, even when we were down at 50,000 feet [15,000 meters], and yet you do have some rough terrain here, but it doesn't appear as sharp-featured or as rugged in a lot of places like on the back side or over this highland area as the Lunar Orbiter photos showed. Over.

LO Lunar Photomap-Censorinus

Lunar Orbiter-Lunar Photomap of the Censorinus area that Stafford is referring to.

Lunar Orbiter V-site 12

(Click on the above chart for a larger version.)

136:16:08 Engle: OK. We copy that, Tom.

136:16:12 Stafford: And that's all three independent conclusions there.

136:16:20 Engle: Roger. Understand.

136:16:36 Stafford: A real rough area is over past Sabine and Ritter where you have strictly a volcanic area; you have these little cones all tossed up. But out here in the highland area - Yes. You've got a lot of slopes and things, but they're definitely not as rugged as what is shown there in those Orbiter photos. Over.

136:16:53 Engle: Roger. Understand. Looks like you could find some places to put down in there. Is that affirmative?

136:17:02 Stafford: Roger. Well, I don't want to try to push it. We'll have to get back on the ground on that one. But out in the mare area, you've got - what we saw yesterday down lower - like to point it out, that's qualitatively 25 to 35 percent smooth. We're in pretty good shape. Over.

136:17:18 Engle: Roger. Understand.

136:17:56 Stafford: Hey, as a matter of fact, for Jack, right here I'm locking right down in Censorinus from 60 miles [111 km] up, and you can see the boulders on that outer edge. And the shadows from them. Over.

136:18:07 Engle: That's pretty amazing, Tom. Those must be pretty good sized rocks down there.

136:18:15 Stafford: Yes. You could make a building or two out of each one of them.

136:18:19 Engle: Roger.

136:18:20 Cernan: We could drop an apple core right in the hole down there.

136:18:25 Engle: Roger.

136:20:39 Stafford: OK. We're passing over Site 2 for the last time around. Over.

136:20:43 Engle: Roger.

136:20:49 Cernan: Hello, Houston. What's your recommendation on a purge here? I turned the heaters on and I'm looking for it in the Flight Plan and I don't see it.

136:20:58 Engle: OK. Did you say a purge, Gene-o?

136:21:05 Cernan: Did you tell me to put the H2 purge line heater on?

136:21:08 Engle: Roger. We wanted the purge line heater on. We anticipate purging number 2 here shortly. We don't want to do it just yet, though.

136:21:17 Cernan: I'll he standing by for some words from you.

136:21:19 Engle: Roger. We do want the heater on though, Gene.

136:21:27 Cernan: It's been on 22 minutes now.

136:21:31 Engle: Very good. Thank you.

136:22:02 Young: You know, you sure don't have any trouble telling a hole from the hills down here.

136:22:08 Engle: Roger.

136:22:09 Young: Like you do in some of those pictures.

136:22:16 Stafford: Right now we're on top of Sabine and Ritter, looking down in the dark shadows [garble] there, but you can see the ramping on the walls and one or two possible big boulders down in there. You know in the pictures it'll show them as black [garble] shadows down below [garble].

136:22:39 Engle: Roger.

136:22:44 Stafford: OK. We checked the P30 and we're about to go through it. We've got the spacecraft configured for TEI [garble] Auto RCS select switches, and everything is strapped down, so we're basically [garble] attitude time around, so as soon as we finish this strip on the landing site here, we're going right to it. [Garble] have any [garble] whether it needs the High Gain. Over.

[Program 30 is used to accept targeting parameters that have been obtained from a source other than the AGC, and using these parameters, compute the required velocity and other initial conditions required by the AGC for execution of the planned maneuver. The parameters required by Program 30 are the time of ignition (TIG) and the impulsive Delta V along the CSM local horizontal vertical axes at TIG. The targeting parameters can be uploaded direct from MCC-H using Program 27. During the execution of Program 30 the External Delta V flag (XDELVFLG) is set to inform the thrusting program (P40) that external Delta V steering is to be used during the maneuver.]

136:23:12 Engle: Roger. Understand, Tom,

136:25:12 Stafford: And we have Landing Site 3 coming up right ahead. It's also marked by the craters [garble].

136:25:20 Engle: Roger, Tom.

136:25:26 Stafford: [Garble].

136:25:57 Stafford: In the area [garble, probably 'between'] Landing Site 2 and Site 3 [garble] the highland area [garble] really marked with a lot of volcanic activity. You can see it all over. You can see the old impact [garble] volcanic activity.

136:26:17 Engle: Eh, roger.

136:26:29 Engle: OK, Apollo 10. This is Houston. We'd like for you to go ahead and purge number 2 fuel cell now for 2 minutes. And we'd also like to have the High Gain antennas as soon as you finish this photography. Over.

136:26:46 Stafford: OK. You got Verb 64 coming at you. And we’ll start - Say you want the fuel cell 2 purged of O2 at this time?

[Verb 64 initiates Routine 05 to compute and display the HGA antenna angles which will point it towards the center of the Earth. Stafford mistakenly believes this is an O2 purge. Engle quickly clarifies that it should be a hydrogen purge.]

136:26:56 Engle: Roger. Fuel cell 2 purged for 2 minutes. That's the hydrogen purge.

136:27:03 Cernan: That's a hydrogen purge, Right?

136:27:06 Engle: That's affirmative, Gene.

136:27:20 Stafford: Purge is started.

136:27:22 Engle: Roger.

136:28:09 Cernan: Hello, Houston. Are you reading us?

136:28:11 Engle: Roger, 10. This is Houston. We're reading you now, Gene.

136:28:16 Cernan: OK. You got Auto track and narrow beam. About three-quarters signal frame. Coming in clear.

136:28:22 Engle: Roger. Understand.

136:28:39 Stafford: OK, Houston. I'm going to go ahead and maneuver to TEI attitude and just fire the pitch. Over.

136:28:45 Engle: Roger. Understand, Tom.

136:29:08 Engle: 10, this is Houston. Tom, could you hold off on that attitude change for a while? We'd like to watch this purge until it's complete.

136:29:21 Stafford: OK. I want to have John get that P52 IMU.

[Stafford is keen to get the CSM to the IMU realign attitude as this P52 realign is vital for the success of the TEI maneuver, so he does not want Young compromised when making this realignment.]

136:29:28 Cernan: And that's 2 minutes on the purge. How's that look to you?

136:29:34 Engle: OK. We're not getting the data down - the high bit rate data down, Gene-o.

136:29:44 Engle: OK. If you've completed the purge...

136:29:45 Cernan: OK. Tell me what you want to do.

136:29:47 Engle: OK. You've completed the purge, so go ahead and maneuver to your attitude. That'll be fine.

136:29:55 Stafford: Roger.

136:29:56 Cernan: OK. The purge is complete and the H2 purge line heaters coming off at this time.

136:30:00 Engle: Roger. Understand. Thank you, Gene.

Air-to-ground audio

136:33:19 Cernan: Houston, how do you read us? 

136:33:22 Engle: Roger, 10. This is Houston. We're reading you ok. Go ahead.

136:33:28 Cernan: OK. Just wondering, Joe. I'm just playing with the Omni's - just playing with the Omnis to hold onto you until we get to the final burn attitude. Then you recommend Delta.

136:33:37 Engle: Roger. That's affirmative. And did you go all the way through P30?

136:33:45 Stafford: We stopped before we got the final countdown. It was over an hour at that time.

136:33:51 Engle: OK.

136:33:54 Stafford: We got the Delta-V's. Over.

136:34:19 Young: Hey, Joe. Did you want us to go all the way through P30?

136:34:25 Engle: Roger. I guess - It appears down here that you didn't get your external Delta-V flag set, John.

[To run Program 30, the crew key on the DSKY Verb 37, Enter, Noun 30, Enter. A flashing Verb 06 Noun 33 displays the uploaded GET for ignition. To accept the ignition time the crew press Pro. Next Verb 06, Enter, Noun 81, Enter is keyed to displayed the uploaded Delta-V in the three axes with respect to the local vertical. To proceed with these values the crew would press PRO. Doing so sets the external Delta-V flag.]

[On this occasion the crew do not press Pro and back out of program 30. This is what MCC-H have noticed and are querying. The external Delta-V flag is set to inform the thrusting program (P40) that external Delta-V steering is to be used during the maneuver.]

136:34:35 Stafford: Yes, we planned...

136:34:37 Young: We didn't go through it. We're going through it as soon as we finish this P52.

136:34:40 Engle: Oh, ok. Mighty fine, then. I'm sorry.

136:34:42 Stafford: Yes, but we plan to go through it again. We just wanted to check - Yes, we just wanted to check that you had the values loaded in there and we got a Comp out of it, you know. We understand.

136:34:51 Engle: OK. Sorry about that. [Garble].

136:35:44 Engle: Apollo 10, Houston.

136:35:49 Stafford: Go ahead.

136:35:50 Engle: Roger. Gene-o, are you on High Gain Antennas, now?

136:35:57 Cernan: That's a negative. I'm on Omni Bravo.

136:35:59 Engle: OK. Thank you very much.

136:36:46 Cernan: Houston, this is 10. I'm going to leave fuel cell 1 on the line until we come around the corner so you can take a look at it, and then we can talk about taking it off.

136:36:57 Engle: OK. That’ll be fine, Gene-o. Thank you.

[Cernan advises MCC-H that he will leave the ailing fuel cell 1 on the main buses until they have AOS for MCC-H to assess its health and for them to advise when it should be taken off the buses as they start the coast back to Earth.]

138:38:24 PAO: We're now about 30 minutes from Loss Of Signal. You heard Gene Cernan report that the spacecraft is configured right now with the omni antennas, which accounts for the somewhat noisy communications we're getting. Apollo 10 is currently at an altitude of 64.6 nautical miles [119.6 km] approaching apogee, which we now show at 68.8 nautical miles [127.4 km]. The spacecraft orbit perigee is 52.8 [97.8 km] and the orbital weight of the Command and Service Module is 36,685 pounds [16,640 kg]. At the present time, the Apollo 10 crew is involved in a Program 52 platform alignment. The purpose of this is to get the stable platform aligned in preparation for the Trans-Earth Injection maneuver.

[Long comm break.]

Air-to-ground audio

136:48:22 Cernan: Hello, Houston. Houston, this is 10. How do you read?

136:48:25 Engle: Roger, Gene-o. Reading you loud and clear. Go ahead.

136:48:30 Cernan: OK. How's that DSKY been looking to you?

136:48:37 Engle: OK. We're watching it. It's looking good, 10.

136:48:43 Stafford: OK. We went through P30 all the way, and now we're just going to do a crew defined maneuver over to the attitude, and then we're going to call P40. Over.

[Now that Young has performed the P52 IMU realignment, the crew are ready to maneuver to the TEI attitude.]

136:48:52 Engle: Roger. Copy. We'll monitor.

136:49:00 Engle: And, 10, this is Houston. I've got some attitudes for your post-TEI TV, if you'd like to copy them down.

136:49:14 Stafford: Stand by.

136:49:15 Engle: Roger.

136:49:18 Cernan: OK, Joe. Go ahead.

136:49:20 Engle: OK. This will be for time 138:00. Use the hatch window, and your attitudes are roll, 180; pitch, 293; yaw, 000. And we'd like the High Gain Antenna angle pitch, minus 58; and yaw, 005. Over.

136:49:50 Cernan: OK. For a time of 138:00, out the hatch window; roll, 180; pitch, 293; yaw, 000; pitch, minus 58; and yaw, 005.

136:50:00 Engle: Read back's correct, Gene.

136:50:02 Young: And, Houston, we have all the Auto RCS switches on. Do you confirm them?

136:50:10 Engle: Roger. Concur, 10. Thank you.

136:50:51 Cernan: Houston, this is 10. I'm going to cycle the cryo fans.

[The fans in the O2 and H2 cryogenic tanks are used to circulate the contents over the tank heating elements to maintain a uniform density and also reduced the chances of stratification in the tank.]

136:50:55 Engle: Roger. Concur.

[Comm break.]

136:50:XX PAO: We're now 16 minutes, 30 seconds from losing contact with Apollo 10. The Flight Director, Milton Windler, has requested that his flight controllers to take a look at all the spacecraft systems and we'll be coming up shortly with the Go/No-Go for Trans-Earth Injection. Flight controllers report all systems Go for TEI.

136:54:16 Honeysuckle Comm Tech: Honeysuckle signal level, minus 105.

136:57:29 PAO: We're coming up now on 10 minutes to LOS. The Guidance Officer here in the Control Center...

[Comm break.]

136:57:49 Engle: Apollo 10, this is Houston. We show about 10 minutes until LOS, and at this time everything looks Go for TEI.

136:58:11 Stafford: Roger. We're going to call up P40 before we have LOS.

136:58:17 Engle: Roger. Understand.

136:58:43 Stafford: OK. The Auto maneuver in P40, we're all set there and trimmed up.

[As part of Program 40, the crew key Verb 50, Enter, Noun 18, Enter to display on the DSKY the FDAI gimbal angles for the TEI attitude, to which an auto maneuver will take the spacecraft. Pushing Pro commences this auto maneuver and the DSKY displays Verb 06 Noun 18 denoting the auto maneuver is underway. The DSKY will again display Verb 50 Noun 18 when the auto maneuver is complete and the spacecraft is at the TEI attitude. The crew follow these steps by aligning the SCS-GDC to the IMU to act as a backup attitude reference. The SPS gimbal motors are energized. Spacecraft control is switched to SCS, the SPS servo check is performed and the manual drive checks are carried out. The spacecraft control is then returned to the CMC.]

The crew push Pro on the DSKY and are presented with a flashing Verb 50 Noun 18. They press Enter and the SPS gimbal is trimmed to the desired burn attitude. The SPS gimbal is now tested and following the test the gimbals are returned to the desired trim settings in readiness for the maneuver.]

136:58:51 Engle: Roger. We copy, Tom.

Flight plan

137:01:06 Young: Houston, could you give us a time hack at 35 minutes countdown?

137:01:11 Engle: 10, say again, please.

137:01:16 Young: Roger. We'd like a time hack around 35 minutes countdown.

137:01:25 Engle: We'll have to give it to you a little before that, John. We show about 6½ minutes until LOS and then you're about 44 minutes. Oh, ok. I'm sorry, we'll get it for you.

137:01:49 Young: Count down the burn, Joe.

137:01:51 Engle: Roger that.

137:02:01 Engle: OK, 10. This is Houston. I can give you a countdown to 34 [minutes]. Will that be ok?

137:02:09 Young: That will be fine.

137:02:11 Engle: Roger that. We're showing 34:12 now. 5, 4, 3, 2, 1.

137:02:27 Engle: Mark.

137:02:28 Engle: 34.

137:02:50 Engle: And, 10, this is Houston. Did you get that, or would you like another countdown?

137:02:58 Stafford: We got it. Give us a mark for 33 [minutes] just to correlate.

137:03:01 Engle: Roger that.

137:03:22 Engle: OK. 33 coming up in 4, 3, 2, 1.

137:03:27 Engle: Mark.

137:03:28 Engle: 33.

137:03:33 Stafford: Roger. We're synced right on.

137:03:35 Engle: Very good, Tom.

137:03:54 Engle: 10, this is Houston. We're showing about 4 minutes until LOS, and that fuel cell 1 is looking good to us right now. Everything looks good for TEI.

137:04:05 Stafford: Roger. We're Go here, and we'll see you on the way home.

137:04:10 Engle: You bet your life. We'll see you in about 41 minutes.

137:04:16 Stafford: OK.

137:05:51 Engle: OK, 10. Houston. We show 2 minutes until LOS. We're still Go; everything looks good.

137:06:00 Stafford: Roger. We're all set here and we'll check the, boresight star [garble] Over.

137:06:05 Engle: Roger.

137:08:04 PAO: And we now have LOS, Loss Of Signal, as Apollo 10 has gone around the corner of the Moon. When next we hear from the crew they should be on their way back to Earth after some 61 hours, 40 minutes. Just to recount the information for the Trans-Earth Injection maneuver; ignition is scheduled to occur at 137 hours, 36 minutes, 28 seconds. The burn duration will be 2 minutes, 41 seconds. That should give the spacecraft an added velocity of 3,630 feet per second [1,106 m/s]. The maneuver will occur at 155 degrees, 43 minutes East longitude, which will be on the back side of the Moon. And with the burn performed properly, we should reacquire the spacecraft at 137 hours, 45 minutes, 26 seconds. As the spacecraft went around the corner of the Moon, as we lost contact, all systems were looking good, all three fuel cells are on the line and performing normally at this time. At 137 hours, 9 minutes; this is Apollo Control.

137:06:38 Stafford (onboard): 2 minutes and 41 seconds burn. Overburn's [garble] You check it.

137:06:51 Young (onboard): 40 feet per second [garble] seconds.

[Young is quoting from the Apollo 10 mission rules, that an SPS maneuver must be terminated manually should an overburn exceed 2 seconds beyond the planned duration or >40 fps (12.2 m/s) above the planned Delta-VC.]

137:07:01 Young (onboard): John, this is two-jet ullage for 14 seconds [garble].

137:07:06 Stafford (onboard): [Garble].

137:07:10 Cernan (onboard): [Garble] Want me to do the sextant star, which should be visible now, possibly - possibly on the horizon in the window?

137:07:17 Young (onboard): OK.

137:07:18 Stafford (onboard): When you back up [garble]. [Garble].

137:07:28 Young (onboard): Tom, I don't mean to be [garble], but [garble].

137:07:36 Stafford (onboard): Yes, [garble] turn it off [garble].

137:07:42 Cernan (onboard): [Garble].

137:07:46 Stafford (onboard): [Garble].

137:08:01 Stafford (onboard): There's [garble] 127:45:56.

137:08:10 Young (onboard): Alright. Sextant star [garble].

137:08:13 Stafford (onboard): All yours.

137:08:30 Cernan (onboard): OK. Verb 41. Noun 91.

[The crew keyed Verb 41, Enter, Noun 91, Enter. A flashing Verb 21 Noun 92 then requests the crew to input the required sextant optics shaft and trunnion angles.]

137:08:32 Young (onboard): Verb 41, Noun 91.

137:08:39 Cernan (onboard): OK, you want the numbers?

137:08:44 Young (onboard): Yes. Give me the numbers.

137:08:41 Cernan (onboard): OK, it's 1 - plus 146.40.

137:08:55 Young (onboard): Go.

137:08:56 Cernan (onboard): Plus 29.400 [garble].

137:09:03 Young (onboard): Plus 464 and [garble].

137:09:15 Young (onboard): Should I load the shaft now?

137:09:18 Cernan (onboard): The star number is 16.

137:09:33 Cernan (onboard): [Garble] Procyon. Got it?

[The sextant shaft and trunnion angles were passed up to the crew as part of the TEI-31 PAD.]

137:09:38 Young (onboard): Yes.

137:09:59 Stafford (onboard): Is [garble] zero?

137:10:01 Young (onboard): Yes, [garble] is zero and [garble].

137:10:13 Stafford (onboard): OK, remember what we said about the oxidizer. In fact, didn't we start it [garble] at [garble]?

137:10:20 Young (onboard): Yes. [Garble] due to what, increase?

137:10:24 Stafford (onboard): [garble].

137:10:49 Cernan (onboard): That's TIG minus 1 minute, John; [Garble]. Horizon should be on the 6-degree window mark. 56:16. OK?

137:11:04 SC: [Garble] 94 [garble].

137:11:08 Young (onboard): [Garble] upside down [garble]. Good show [garble] on the horizon [garble]. [Garble].

137:11:29 Cernan (onboard): OK [garble].

137:11:34 Stafford (onboard): [Garble] watch, 28 minutes of [garble].

137:11:41 Young (onboard): [Garble], Gene-o?

137:11:45 Cernan (onboard): Yes, [garble].

137:11:47 Young (onboard): [Garble] right down 248 [garble], OK. OK - ok. Now, in the event we have to go to SPS, [garble].

137:12:00 Stafford (onboard): OK.

137:12:01 Young (onboard): [Garble] the whole works [garble] forget that. Now don't forget to remind me [garble].

137:12:08 SC: [Garble] here.

137:12:09 Young (onboard): No, right after [garble]...

137:12:16 Cernan (onboard): That's the only way you can get [garble] down [garble]...

137:12:17 Young (onboard): ...[garble].

137:12:19 Stafford (onboard): [Garble] fuel.

137:12:26 Young (onboard): [Garble].

137:12:36 Stafford (onboard): [Garble] ullage, LOS [garble].

137:12:43 Cernan / Young (onboard): [Garble].

137:12:51 Stafford (onboard): You want to open the vent, or do you want me to?

137:12:54 Young (onboard): I'll open it.

Rev 32 spacecraft attitude diagram

Planned spacecraft attitudes during rev 32.

(Click on above diagram for larger image.)

137:13:-- BEGIN LUNAR REV 32

137:13:11 Stafford (onboard): Yes.

137:13:12 Cernan (onboard): You got the [garble]?

137:13:14 Stafford (onboard): Yes. The [garble] is 2 feet [garble] 2 [garble] per second.

137:13:19 Cernan (onboard): OK.

137:13:23 Stafford (onboard): And it's better than [garble] shutoff on that, over [garble]. Then [garble] 2 seconds [garble].

137:14:57 Cernan (onboard): Is that normal?

137:14:59 Young (onboard): [Garble].

137:15:23 Cernan (onboard): You should have - 21 minutes and - [garble].

137:15:28 SC: OK.

137:15:29 Cernan (onboard): Huh?

137:15:32 SC: OK, [garble].

137:15:35 Young (onboard): [Garble] as far as I can tell.

137:15:39 Stafford (onboard): [Garble].

137:15:43 Young (onboard): [Garble].

137:15:45 Cernan (onboard): Look at that.

137:15:52 Young (onboard): [Garble].

137:17:50 Young (onboard): That SEP burn - that SEP maneuver probably pushed all the damn fuel up in front of the spacecraft anyway. There should be a little more ullage. [Garble] SEP maneuver.

[Young is commenting on the amount of ullage burn required to settle the SPS propellants near the tank outlets at the rear end of the Service Module. He feels the CSM SEP maneuver to separate it from the jettisoned LM Snoopy ascent stage will have moved the propellants to the forward end of the tanks. MCC-H have advised on the degree of ullage required, using 2 SM RCS for 14 seconds.]

137:17:59 Cernan (onboard): Roger; man, we're doing [garble].

137:18:33 Young (onboard): Why is that fuel cell light on it? It's - You know, anybody?

137:18:37 Stafford (onboard): We got the pump off of it.

137:18:38 Young (onboard): [Garble] and the condenser-exhaust temperature is off-scale low.

137:18:42 Young (onboard): Oh, [garble].

137:19:14 Stafford (onboard): You have 17 minutes.

137:19:18 Young (onboard): All these switches seem to still be in the same position that they were before.

137:20:59 Young (onboard): How are them batteries, Gene-o?

137:21:03 Cernan (onboard): The batteries are in good shape.

137:21:05 Young (onboard): What's this charge? You keep turning them on and off? What's that for?

137:21:09 Cernan (onboard): To keep charging them. I'm going to have to do it again after this burn, because they - they come down, of course.

137:21:16 Stafford (onboard): How much we got?

137:21:18 Cernan (onboard): Gimbal [garble, probably 'motor'] sucks a lot out of them; battery B's never been charged. but it's A and B all the time, you know. Besides, they're on the battery bus, and there's a certain amount of current drained.

137:21:31 Young (onboard): I know that. Some sunset - sunrise is like that 5 minutes before the burn, isn't it? Burn at sunrise, Gene-o.

137:21:46 Stafford (onboard): I don't think they passed that up.

137:21:50 Young (onboard): [Garble]. What time is it on that Flight Plan? TEI?

137:22:08 Stafford (onboard): Ohh! Where'd it go?

137:22:11 Young (onboard): Next page.

137:22:14 Cernan (onboard): Would you believe we could damn near burn TEI with that criteria and get away with it?

137:22:16 Stafford (onboard): 37:20.

137:22:18 Young (onboard): Right at the sunrise, isn't it?

137:22:20 Stafford (onboard): The sunrise here is about - we'll call it 10, and we'll be running what...

137:22:25 Young (onboard): 10 minutes before.

137:22:27 Stafford (onboard): OK.

137:22:28 Young (onboard): The sun will be way above us, because we've got another 3 degrees [garble].

137:22:32 Cernan (onboard): Yes. Sun will be well above us.

137:22:37 Young (onboard): Alright, [garble].

137:22:43 Stafford (onboard): Do you see it, Gene-o?

137:22:46 Cernan (onboard): The Sun?

137:22:47 Stafford (onboard): No, no.

137:23:27 Cernan (onboard): I'm going to come out [garble] and mark 13 minutes from the burn.

137:23:29 Young (onboard): Good show.

137:23:41 Stafford (onboard): OK, [garble] it's beautiful. Once he gets out the window, we can take a look at [garble].

137:23:50 Young (onboard): I want to be coming along...

137:24:02 Stafford (onboard): Pointed down...

137:24:03 Cernan (onboard): John, the horizon is on a 6-degree mark on the window, at TIG minus 1 minute.

137:24:08 Stafford (onboard): Yes, we - we're here coming up like that. And we'll be coming up to it inertial. We're still pointed down. The Sun's hitting our windows good and [garble] then. We're pointed down.

137:24:47 Cernan (onboard): We'll be - we'll be - we'll be face up, won't we?

137:24:50 Stafford (onboard): You're upside down...

137:24:51 Cernan (onboard): Oh, upside down. Yes.

137:24:52 Stafford (onboard): You're upside down, yes. Pointed down and coming up. Inertial angle, coming up.

137:25:11 Stafford (onboard): You want to take that? I got it.

137:25:26 Young (onboard): Oh, shit. [Garble] the goddam [garble].

137:25:36. Stafford (onboard): OK, coming up in 10 minutes, babe.

137:25:39 Young (onboard): [Garble] one more time.

137:25:42 Cernan (onboard): Do it again; but, offhand, it doesn't cycle. Delta-V checks. That Delta-V [garble] Delta-V [garble].

137:25:49 Stafford (onboard): Yes. 36077.

137:25:50 Young (onboard): BMAGs, Rate 2...

[Placing all three BMAGs in Rate 2, prevents BMAGs from hitting stops during the maneuver.]

137:25:52 Stafford (onboard): BMAGs.

137:26:02 Young (onboard): They are on. OK, load the DAP, and we'll go to Spacecraft Control, CMC and Auto, [garble].

137:26:14 Stafford (onboard): You done that?

137:26:15 Young (onboard): Right.

137:26:16 Cernan (onboard): Is your clock - coming up on 10 minutes on the clock?

137:26:19 Young (onboard): Yes. And 10 seconds...

137:26:25 Cernan (onboard): [Garble].

137:26:28 Cernan (onboard): Mark.

137:26:29 Young (onboard): Mark it, yes.

137:26:31 Stafford (onboard): 12, Closed.

137:26:37 Young (onboard): Yes, 12, Closed. All Closed. OK.

137:26:58 Cernan (onboard): You have 12 Closed?

137:27:01 Young (onboard): Manual Attitude, three, Rate Command. Attitude Deadband, Min; and got that [garble] High; [garble] Translational Control Power is On; Rotational Control Power, Direct, is Off; [garble] Auto [garble] Rate Command [garble] Auto [garble] 6 minutes.

137:27:25 Cernan (onboard): OK, I've checked all the circuit breakers [garble].

137:27:40 Cernan (onboard): There's the Moon.

137:27:41 Stafford (onboard): You can see it? [Garble] we're going posigrade. That's a good sign, Gene-o.

137:27:50 Cernan (onboard): A hopeful sign.

137:27:54 Young (onboard): Where is the Moon?

137:27:55 Cernan (onboard): Right straight ahead of you, John.

137:27:57 Stafford (onboard): I don't think...

137:27:58 Cernan (onboard): You're - No, this way, this way.

137:28:01 Young (onboard): Yes, I can't see much...

137:28:03 Cernan (onboard): Huh?

137:28:06 Stafford (onboard): OK, when do you want to make a last trim on this thing?

137:28:09 Young (onboard): Well, we got a ways to go...

137:28:11 Stafford (onboard): Yes,

137:28:12 Young (onboard): ...about 6 minutes to go.

137:28:14 Stafford (onboard): Coming up to 6 minutes, to the Main Bus Tie.

137:28:19 Young (onboard): 8 minutes now.

137:28:30 Cernan (onboard): Now does your pitch look on the ball...

137:28:34 Young (onboard): Looks better.

137:28:52 Stafford (onboard): There we go [garble] posigrade.

137:29:08 Young (onboard): I was a little worried there for a second. I thought maybe we didn't get there in time.

137:29:12 Stafford (onboard): Yes, just about the same thing we saw when we got in except we were going backwards.

137:29:17 Young (onboard): Yes, right.

137:29:19 Stafford (onboard): Well, that looks gray and white when you first see it. Well, back in the cockpit, 7 minutes, coming up 6 to the Bus Tie.

[Main Bus Tie Bat A/C to On, Main Bus Tie Bat B/C to On, on panel 5, provide additional electrical supply to both buses and additional redundancy should the fuel cells be unable to handle the electrical load during the upcoming TEI maneuver.]

137:30:18 Young (onboard): OK, Gene-o; 6 minutes - 6 minutes.

137:30:21 Cernan (onboard): 6 minutes; stand by on the [garble].

137:30:24 Stafford (onboard): OK. Got them? OK, TVC Servo Power, AC1/MNA.

137:30:35 Young (onboard): Go.

137:30:36 Stafford (onboard): AC2/MNB

[Power is provided to the TVC servos.]

137:30:37 Young (onboard): Go.

137:30:40 Stafford (onboard): Rotational Control Power, number 2, AC.

137:30:41 Young (onboard): AC.

137:30:42 Stafford (onboard): Rotational Control, number 2, armed.

[Opens RHC 2 (commander's) breakout switch (DC circuits) to prevent attitude maneuvers, through CMC during MTVC (manual thrust vector control) servo checks.]

137:30:44 Young (onboard): Go.

137:30:45 Stafford (onboard): OK, let me make a final trim here. OK?

137:30:49 Young (onboard): Yes.

137:30:58 Stafford (onboard): Rotational Control 2, armed. We got that. Go. 5 minutes.

137:31:02 Cernan (onboard): OK, standby [garble].

137:31:03 Stafford (onboard): You want to go ahead and get them on already?

137:31:16 Young (onboard): OK. OK, Pitch [garble] number 1 coming On.

137:31:21 Young (onboard): Mark.

137:31:22 Cernan (onboard): Go.

137:31:23 Stafford (onboard): Yaw 1.

137:31:24 Young (onboard): Mark.

[The primary Gimbal Motors are switched on sequentially at least 1 second apart to avoid electrical overload.]

137:31:25 Cernan (onboard): Go.

137:31:26 Stafford (onboard): Translational Control, clockwise.

137:31:28 Young (onboard): Clockwise.

[Rotating the THC clockwise enables manual thrust vector control and switches the TVC to channel 2.]

137:31:29 Stafford (onboard): Verify no MTVC.

137:31:30 Young (onboard): No MTVC.

[Using the RHC-2 to confirm that the TVC has switched to channel 2, which is currently Off, checks that there is no manual thrust vector control.]

137:31:31 Stafford (onboard): Secondary TVC check. Gimbal Motors...

137:31:34 Young (onboard): Coming On.

137:31:36 Young (onboard): Mark.

137:31:37 Cernan (onboard): Go.

137:31:38 Young (onboard): Yaw 2 coming On.

137:31:39 Young (onboard): Mark.

[The secondary Gimbal Motors are switched on sequentially at least 1 second apart to avoid electrical overload.]

137:31:40 Cernan (onboard): Go. You got them all. John.

137:31:41 Stafford (onboard): OK. Except trim.

137:31:42 Young (onboard): Trim was what?

137:31:43 Stafford (onboard): Minus 0.62 and plus 0.89.

[The SPS Gimbal thumbwheels are set to the center-of-mass trim values given to them by MCC-H.]

137:31:49 Cernan (onboard): That's go.

137:31:50 Stafford (onboard): Plus 0.89.

137:31:54 Cernan (onboard): OK. I'll put them up just a little...

137:31:57 Stafford (onboard): OK.

137:31:58 Cernan (onboard): ...because CMC trim's in just a little high...

137:31:59 Stafford (onboard): OK. Check MTVC.

137:32:01 Cernan (onboard): MTVC [garble].

[Again using the RHC-2, the crew confirm that the that there is manual thrust vector control.]

137:32:02 Stafford (onboard): OK, neutral.

137:32:04 Cernan (onboard): Neutral [garble] goes to zero.

[Returning RHC-2 to the neutral position returns the TVC to the trim position.]

137:32:07 Stafford (onboard): Zero. Rotational Control Power, Normal. number 2. AC/DC.

137:32:11 Cernan (onboard): Go.

137:32:13 Stafford (onboard): Check the boresight star - you got that. Trim. Ready for the Auto trim.

137:32:18 Young (onboard): Yes, go.

137:32:19 Stafford (onboard): Ready. Proceed. Plus 2, minus 2, and zero; plus 2, minus 2, and zero. Now for the trim. OK. Minus about 0.6, and plus nearly 1. It looks good shutting down at 349; we're Synced.

[The final Auto attitude trim is carried out.]

137:32:42 Cernan (onboard): Helium Valves to Auto.

137:32:44 Young (onboard): OK, Rotational Control Power, Direct, MNA/B.

[This enables manual direct RCS control for overriding an auto RCS roll failure during SPS thrusting.]

137:32:46 Cernan (onboard): They are Auto.

137:32:49 Stafford (onboard): Limit Cycle, Off.

137:32:50 Young (onboard): [Garble], Off.

137:32:53 Stafford (onboard): FDAI as desired.

137:32:54 Young (onboard): As desired.

137:32:55 Stafford (onboard): GDC Align. BMAG, Att 1/Rate 2.

137:33:10 Young (onboard): Go.

[The GDC is once again aligned to the current IMU orientation to provide a backup attitude reference.]

137:33:12 Stafford (onboard): OK. At minus 2 minutes. Delta-V Thrust A and B. Normal.

137:33:19 Cernan (onboard): OK, John, the only thing I got left is that 6-degree window mark on the horizon at 1 minute.

137:33:27 Young (onboard): OK.

137:33:29 Cernan (onboard): [Garble] it's going to be ok.

137:33:32 Young (onboard): OK.

137:33:53 Young (onboard): OK, don't forget to go to High Bit Rate at 30 seconds.

137:33:57 Cernan (onboard): OK. that [garble] 34 at 228 [garble].

137:34:02 Stafford (onboard): OK, count up to 2 minutes. Then we'll get Delta-V Thrust A, Normal, and then you'll get B at 3 seconds.

137:34:10 Young (onboard): Right.

137:34:11 Stafford (onboard): After B goes on, then Gene-o will take care of the [garble].

137:34:16 Young (onboard): OK.

137:34:17 Stafford (onboard): Rotational Control Power, Normal.

137:34:19 Cernan (onboard): Rotational Control Power, Norm.

137:34:21 Stafford (onboard): OK. Delta-V switch A, On.

137:34:26 Young (onboard): Go.

137:34:28 Stafford (onboard): OK, you got the Translation to On?

[The THC is armed for the final time.]

137:34:31 Young (onboard): On.

137:34:32 Stafford (onboard): You had the Rotational Control Power to ON?

[Both RHC are armed.]

137:34:33 Young (onboard): On.

137:34:34 Stafford (onboard): Next check is minus 30 seconds; that's the EMS, Delta-V Normal, and the High Bit Rate to Gene-o.

137:34:39 Cernan (onboard): OK, John, you did have your 8-balls out, huh?

137:34:45 Young (onboard): [Garble] just two.

137:34:46 Cernan (onboard): Your 8-balls out!

137:34:47 Young (onboard): Yes.

137:34:48 Stafford (onboard): Got 8-ball [FDAI] [garble]...

137:34:50 Young (onboard): OK, just wanted to verify..

137:34:54 Stafford (onboard): OK, you want plus-X ullage at minus 14 seconds. You can give it 15 if you want to.

[The crew want to ensure they get a good start to the TEI maneuver, so they are discussing firing the SM RCS for an additional second beyond the 14 seconds specified by MCC-H. They want to ensure the remaining propellants in the SM tanks are settled to the rear end of the spacecraft near the tank outlets.]

137:34:57 Young (onboard): OK, you bet your ass I want to. Alright...

137:35:02 Cernan (onboard): Don't give it 13; give it 15.

137:35:05 Young (onboard): OK, that's 1-minute window check; let's go.

[The prediction given by MCC-H of the horizon being seen on the 6-degree mark in the rendezvous window, proves to be spot on. This gives confidence in the spacecraft attitude in preparation for the TEI maneuver.]

137:35:07 Stafford (onboard): OK.

137:35:08 Cernan (onboard): OK.

137:35:09 Young (onboard): Just perfect, as a matter of fact.

137:35:11 Stafford (onboard): Beautiful!

137:35:22 Young (onboard): 1 minute; next check at 30 seconds.

137:35:28 Cernan (onboard): 1 minute, babe.

137:35:30 Stafford (onboard): Oh, shit, that thing's counting backwards, but that's ok.

137:35:35 Cernan (onboard): Well, I have my watch going.

137:35:38 Stafford (onboard): OK. At 30 seconds, EMS, Delta-V Normal, and High Bit; Gene-o, you can go ahead and get it now, if you want to.

137:35:44 Cernan (onboard): I should - I should be strapped in the couch really. Freak, I don't know.

137:35:54 Stafford (onboard): DSKY blanks - EMS, Delta-V, Normal. OK, stand by for ullage in 15 seconds, John...

[The UP TLM CMD switch is moved to Rset then Norm. The PCM Bit Rate switch is set to Hi to ensure high bit rate data is recorded during the maneuver. EMS Mode switch is placed to Norm less than 30 seconds prior to thrusting to minimize buildup of Delta-V indicator errors, caused by accelerometer bias.]

PAO audio

137:36:XX PAO: This is Apollo Control; 137 hours, 36 minutes. We're now less than 1 minute from the time at which the Apollo 10 crew will be igniting their 20,500-pound thrust Service Propulsion System engine to start them back to Earth. At this time, the crew should be completing last minute checks of their guidance and navigation system. They should have gotten the spacecraft into proper attitude and checked that attitude against stars. At about 35 seconds prior to the engine ignition, their computer display panel will blank briefly. They'll then follow that with some last minute checks of the accelerometers in the guidance system. At 14 seconds prior to ignition, two of the RCS, Reaction Control System, jets will come on to settle SPS propellants. And at minus 5 seconds, a flashing light on the DSKY, the computer display panel, will request the crew to enable the engine for ignition, if all is Go at that point. John Young will punch a button to Proceed and the engine will ignite on schedule. We now show 25 seconds to ignition.

[The SPS Thrust light on panel 1 illuminates indicating that the SPS engine has ignited at 137:36:28.9 for its last major maneuver to inject the spacecraft onto a trajectory which will result in the CM entering Earth's atmosphere in the middle of the re-entry corridor.]

137:36:50 Cernan (onboard): [Garble] looking good here.

137:36:52 Stafford (onboard): EMS agrees.

137:36:54 Young (onboard): Steering good, chamber pressure is 102.

[The PC indicator on panel 1 provides the SPS chamber pressure reading.]

137:36:56 Cernan (onboard): [Garble] pressures are Go, ball valves are Go.

[The SPS INJ VLV indicators (4) on panel 3 all show the valves are Open.]

137:37:02 Stafford (onboard): 2 minutes to go.

137:37:03 Cernan (onboard): 35 seconds into the burn.

137:37:05 Stafford (onboard): OK, it looks good.

137:37:07 Young (onboard): Steering good.

137:37:13 Cernan (onboard): Looks like the time is going to be about 02:43.

137:37:15 Stafford (onboard): Yes.

137:37:17 Cernan (onboard): Everything's Go.

137:37:19 Young (onboard): 102-psi chamber pressure.

137:37:22 Stafford (onboard): Steering looks good, John...

137:37:23 Young (onboard): Gone Off and coming back Of. 102 psi.

137:37:27 Cernan (onboard): OK, we're...

137:37:28 Cernan (onboard): Mark.

137:37:29 Cernan (onboard): One minute into the burn.

137:37:30 Stafford (onboard): Roger.

137:37:32 Young (onboard): [Garble]. OK, gang, it looks like it's counting good.

137:37:37 Stafford (onboard): Go, baby; [garble] go.

137:37:39 Cernan (onboard): Burn's looking good. Pressures are holding. Ball valves...

137:37:44 Young (onboard): [Garble] down, 104.

137:37:52 Cernan (onboard): OK, we've got about a minute 20 seconds to burn.

[Stafford commented on the attitude changes during the TEI burn in the post mission debrief.]

Stafford, from the 1969 Post Mission Debrief:- "The ignition was on time. We had some rates to start with, but within approximately 30 seconds, the rate damped down. For the last few minutes of the burn, the pitch and yaw rates were absolutely zero, but roll would continually go back and forth in the deadband."]

137:37:54 Young (onboard): The chamber pressure's 102 and holding.

137:37:56 Stafford (onboard): OK.

137:37:59 Cernan (onboard): [Garble]. Burn, baby, burn.

137:38:01 Young (onboard): [Garble].

137:38:04 Stafford (onboard): [Garble].

137:38:09 Cernan (onboard): OK. We've got about a minute to burn, John.

137:38:11 Stafford (onboard): That's right.

137:38:12 Young (onboard): Roger.

137:38:14 Cernan (onboard): Everything's Go in here.

137:38:16 Young (onboard): OK. good.

137:38:30 Cernan (onboard): OK, we got 40 - 44 seconds to burn.

137:38:33 Stafford (onboard): EMS [garble], Gene-o; it's beautiful. Beautiful, beautiful correlation.

137:38:40 Cernan (onboard): It's all here, babe.

PAO: Coming up on 30 seconds now to shutdown.

137:38:41 Stafford (onboard): [Garble] 30 seconds, 29...

137:38:48 Cernan (onboard): Valves and PUGS are all Go.

137:38:49 Stafford (onboard): ...25...

137:38:51 Young (onboard): [Garble].

137:38:53 Cernan (onboard): OK, John, the normal. shutdown is at 43. Coming up on 29 - 30. Shutdown on 43. There's 35, 6, 7, 8, 9, 40, 1, 2, 3. 4...

137:39:15 Stafford (onboard): It's off. [Garble] valves, Off; Gimbal Motors, Off. Gimbal Motors [garble].

PAO: And at this point the SPS engine has shut down, Apollo 10 on its way back to Earth. We should reacquire, we should acquire the spacecraft in about 9 minutes from now. We anticipate that when the spacecraft comes around the corner of the Moon on its way back to Earth, the crew will have the television camera on and we would hope to have television pictures of the Moon receding in the background. Now this television will come to us from the site at Honeysuckle, Australia, where we'll be using the 85-foot [26 metre] dish antenna at this site. This introduces the possibility that the signal will not be as strong as the reception we would get on the 210-foot [64 metre] dish at Goldstone. However, tests have shown that this should be adequate.

[The SPS engine has shut down after a burn duration of 164.8 seconds, providing an additional Delta-V of 3,680.3 fps (1,121.8 m/s).]

[The SPS INJ VLV indicators (4) on panel 3 good to Closed. The SPS He VLV (2) talkbacks go to barber pole. The secondary Gimbal Motors are switched Off, followed by the primary. A flashing Verb 16 Noun 40 signifies the SPS cut-off. The DSKY displays VG (velocity gained) as xxxx.x fps and the accumulated Delta-V again as xxxx.x fps.]

137:39:19 Young (onboard): ...2, 3, 4...

137:39:22 Stafford (onboard): TVC Servo Power. Proceed.

137:39:23 Young (onboard): ...Off. OK.

137:39:26 Stafford (onboard): Beautiful. 0.3. OK, plus 0.3, plus 1.6, minus...

Stafford, from the 1969 Post Mission Debrief:- "The residuals were absolutely fantastic. We had 0.3 feet per second X (0.09 m/s), which we reduced to 0.2 (0.06 m/s), as by the predefined mission rules. The VGY was 1.6 feet per second (0.5 m/s), and VGZ was minus 0.2 feet per second (0.06 m/s)."

Young, from the 1969 Post Mission Debrief:- "Delta-VC was 19.9 (fps, 6.1 m/s) which speaks very well of the EMS. We could have confidently done an EMS burn."]

137:39:30 Cernan (onboard): Where's the - give me the Flight Plan.

137:39:32 Stafford (onboard): Go ahead. I'll - I'll tell him. OK, ullage flow, John; just a little bit.

137:39:35 Young (onboard): OK.

137:39:38 Stafford (onboard): There we are, 0.1. Residuals, plus 0.1, plus 16, minus 0.2, plus 1, plus 0.2. I'm going to Proceed. That should be plus 0.2, plus 16, and minus 0.2. Whew! Baby, we [garble]. Got to do a Verb 6...

137:39:59 Young (onboard): What all do we have to do now? Delta-V Thrust A and B switches, Off. They're Off. Gimbal Motors are Off.

137:40:06 Stafford (onboard): Yes.

137:40:07 Cernan (onboard): OK, we're still in the [garble] highest 19.9?

137:40:14 Young (onboard): TVC Servo Power 1 and 2, Off.

137:40:16 Cernan (onboard): Yes.

137:40:11 Young (onboard): Main Bus Ties are Off.

137:40:19 Cernan (onboard): They're Off.

[The Main Bus Ties are taken off removing the batteries from the buses, conserving them for later midcourse corrections and entry in Earth's atmosphere.]

137:40:20 Young (onboard): OK. You can pull those breakers, if you want to.

137:40:22 Cernan (onboard): BMAG, three, Rate 2...

137:40:24 Young (onboard): [Garble] Rate 2, EMS to Standby.

[Delta-ΔV indicator errors can be minimized by setting the EMS Mode switch to STBY immediately after thrusting.]

137:40:26 Cernan (onboard): OK.

137:40:29 Young (onboard): Roger. Residuals nulled, High Bit Rate to Low Bit Rate.

[Now that the maneuver is complete, the data recording bit rate is returned to Low.]

137:40:34 Cernan (onboard): Burn time is 02:44.

137:40:31 Stafford (onboard): Oh, hey, babe, that looks better.

137:40:39 Young (onboard): Yes, sure [garble] on that one [garble] the old clammy hands.

137:40:42 Cernan (onboard): Oh, babe. Good show. Now we're on our way home.

137:40:46 Young (onboard): What do we - what do we do now? (Laughter)

137:40:47 Cernan (onboard): What?

137:40:48 Young (onboard): What does it say to do now?

137:40:49 Cernan (onboard): I'm going to get out my music! (Laughter)

137:40:51 Stafford (onboard): Let's tell them we're on our way back to the Earth, and after everything settles down - we're on the way back. OK. Shoot, I need to climb [garble] OK, let's get the Flight Plan out...

137:41:00 Young / Cernan (onboard): [Garble].

137:41:01 Stafford (onboard): Oh, here we go; Verb 66. You got the Flight...

137:41:02 Cernan (onboard): Get a Verb 66...

137:41:03 Young (onboard): Verb 66.

[Verb 66 is used to transfer the current CSM state vector to the LM storage slot in the CMC.]

137:41:04 Stafford (onboard): ...Verb 66 [garble].

137:41:07 Cernan (onboard): OK. babe. You want to - want to maneuver for High Gain. Go to roll, 180; pitch, 29 - That's at - that's at 138. but that's the same High-Gain attitude.

137:41:16 Stafford (onboard): Yes.

137:41:17 Cernan (onboard): Roll, 138; pitch...

137:41:19 Stafford (onboard): OK.

137:41:20 Cernan (onboard): ...293; and yaw, zero.

137:41:21 Stafford (onboard): Roll - roll, 180; pitch, 293...

137:41:22 Young (onboard): Now start pitching.

137:41:24 Stafford (onboard): OK pitch to 293.

137:41:27 Young (onboard): Do it this way.

137:41:28 Stafford (onboard): OK. Verb [garble]. What do you want? 180?

137:41:31 Young (onboard): Yes. You are at 180.

137:41:36 Stafford (onboard): Which way? 293.

137:41:39 Young (onboard): Yes.

137:41:43 Cernan (onboard): Should I log that in, until we get Houston?

137:41:50 Young (onboard): OK. let's - Well. let's do it this way. Right 003 [garble]...

137:41:56 Stafford (onboard): [Garble] falling. Got two [garble] wheel pitches right around [garble] the switch...

137:42:02 Young (onboard): ...9218. 10102.

137:42:07 Cernan (onboard): Good show, guys. Tom. you going to be up [garble]?

137:42:15 Stafford (onboard): Yes.

137:42:16 Cernan (onboard): [Garble].

137:42:21 Stafford (onboard): OK. we're making [garble].

137:42:23 Young (onboard): Half a degree a second, there.

137:42:25 Stafford (onboard): Bet you one thing. You can control pitch [garble] and yaw in quads [garble] on that thing. We've still got all kinds of [garble]...

137:42:33 Young (onboard): Which one were we using before? Were we using, you know...

137:42:35 Stafford (onboard): Turn off - turn A Pitch, Off. Turn A Pitch, Off. One-half doesn't matter.

137:42:43 Young (onboard): Let's see - Oh, hell [garble]. How much gas we got?

137:42:46 Stafford (onboard): Well, there's - That's our lowest quad - there's A, there's B. There's C, and there's D.

137:42:53 Cernan (onboard): [Garble] I knew it would work. I just had to wait and see.

137:42:57 Stafford (onboard): Goodbye, [garble] shelf. Adios. Oh-ho.

137:43:03 Cernan (onboard): Did it feel like it did in the simulator?

137:43:04 Stafford (onboard): Just getting warmed up...

137:43:05 Young (onboard): The High Gain Antenna angles are minus 58 and 5.

137:43:08 Cernan (onboard): Minus 58 and plus 5.

137:43:11 Young (onboard): Yes. Got the postburn report all made up?

137:43:15 Cernan (onboard): Yes. It's in there. [Garble].

137:43:18 Young (onboard): OK. It was 0.3 VGX and we took - took it to...

137:43:22 Stafford (onboard): 0.2.

137:43:23 Young (onboard): It was 0.3?

137:43:24 Stafford (onboard): Yes.

137:43:25 Young (onboard): Yes.

137:43:26 Cernan (onboard): Tom, this yours since you're the hatch-window man...

[Cernan is passing the color TV camera to Stafford to shoot the receding Moon through the hatch window.]

137:43:32 Stafford (onboard): Push a button, babe. (Sigh)

137:43:37 Cernan (onboard): Don't forget the water...

137:43:39 Young (onboard): Hey, man, we may be able to do away with those cards.

137:43:43 Stafford (onboard): All-hah.

137:43:45 Young (onboard): You knew damn well I [garble].

137:43:47 Stafford (onboard): Let's see; I this the best words are - to start with, are 'Houston, we're on our way back to the Earth.'

137:43:54 Young (onboard): OK. You start with [garble].

137:43:57 Stafford (onboard): Oh, shit [garble].

137:43:58 Cernan (onboard): [Garble] Man, we're home - coming home.

137:44:05 Young (onboard): (Sigh) [Garble] Power, Off.

137:44:08 Cernan (onboard): [Garble].

137:44:11 Young (onboard): That three-ten - that three-quarters of a g felt like a ton (laughter)...

137:44:13 Stafford (onboard): That's what I...

137:44:14 Young (onboard): ...I couldn't raise my head!

137:44:15 Stafford (onboard): How much fuel you got left, babe?

137:44:16 Young (onboard): Holy smokes.

137:44:17 Cernan (onboard): Not much, babe, because that unbalance is - the PUGS is not working [garble].

[Cernan commented on the PUGS operation during the TEI burn during the post mission debrief.]

Cernan, from the 1969 Post Mission Debrief:- "Throughout that whole burn, the PUGs was on the full increase side of the meter. The increase switch was put to Full Increase after the second bank A valves were put in, so that we would not get any start transient in case there might have been one with the flow valve movement. So, after we got a good solid secondary set of ball valves open, we went to Full Increase, and it never did anything. The unbalance continued the percentages continued to get further away."]

137:44:21 Stafford (onboard): So it's 6 percent in fuel and 9 percent in oxidizer.

137:44:25 Cernan (onboard): [garble].

PAO: We're coming up on 1 minute to Acquisition Of Signal. Flight Director Milton Windler has asked his flight controllers to stand by to get a first look at the spacecraft systems as Apollo 10 comes back around the other side of the Moon en route to Earth.

137:44:21 Stafford (onboard): We're around the corner, baby; we're there.

137:44:32 Cernan (onboard): AOS...

137:44:33 Stafford (onboard): Oh, are we close!

137:44:34 Cernan (onboard): AOS is at 45:26.

137:44:49 Stafford (onboard): Boy, look at that Moon go away. Wait until it gets out there and starts to getting round; that's when we can get that color stuff.

[Stafford was a vocal proponent of taking colour television on Apollo.]

137:44:56 Cernan (onboard): [Garble].

PAO: And we're coming up on 30 seconds now to Acquisition Of Signal. And we should have Acquisition Of Signal shortly.

137:45:00 Stafford (onboard): What time did we burn away from the Moon? What time was that burn?

137:45:04 Young (onboard): Oh, it was on time, whatever it was.

137:45:06 Stafford (onboard): 1 - Yes, here it is, 13...

137:45:10 Young (onboard): 137:36:28.20. Translation Control Power, Off. ACS, On.

137:45:32 Stafford (onboard): Oh-ho-ho, look at that bear.

[Stafford has noticed the different view of the Moon below, now that they have left lunar orbit. They are quickly rising away from the Moon and it is becoming noticably more spherical in its appearance as more of the globe fills their view.]

137:45:34 Young (onboard): Do you see the world?

137:45:35 Stafford (onboard): Look - no, but look. at that bear. Look at that bear down there. Beautiful! It's good to see it from this way.

137:45:41 Young (onboard): Yes. Feel like it's far.

137:45:46 Stafford (onboard): Is that them?

137:45:47 Young (onboard): Yes.

[Stafford has detected the communications carrier in his headset, and realizes they have AOS.]

PAO: There is the word, "AOS Flight". We have telemetry data, we're standing by for voice communications from the Apollo 10 crew.

137:45:48 Cernan (onboard): Here. Wait a minute. Let me get - let me get down there. [Garble].

137:45:52 Stafford (onboard): Let's wait until everything...

137:45:53 Young (onboard): [Garble] on there.

137:45:54 Stafford (onboard): ...settles down, and then we might play one stanza [garble].

137:45:55 Cernan (onboard): Yes. Yes. That's a prewinder. Oh, [garble] Are you there?

137:46:05 Young (onboard): Just way back, about...

Air-to-ground audio

137:46:06 Engle: Apollo 10, this is Houston. We are standing by.

137:46:07 Cernan (onboard): [Garble].

137:46:11 Stafford (onboard): Can we talk?

137:46:25 Stafford: Hello, Houston. Apollo 10.

137:46:27 Engle: Hello, Apollo 10. This is Houston. How did the burn go?

137:46:32 Stafford: Roger, Houston. We are returning to the Earth. Over.

137:46:38 Engle: Glad to have you on the way back home, 10.

137:46:43 Stafford: Roger. The burn was absolutely beautiful and Gene-o has a report, and we have a fantastic view of the Moon now. Over.

137:46:51 Engle: Mighty fine, Tom. Standing by for that report.

137:46:56 Cernan: Hey, Joe. You've got an 'atta boy' for that PAD update. Here it comes: burn was on time: it was 2 minutes and 44 seconds. Residuals were plus 0.3 [fps, 0.09 m/s] which were reduced to 0.2 [fps, 0.06 m/s], plus 1.6 [fps, 0.5 m/s] and minus 0.2, Delta-VC is minus 19.9 [fps, 6.07 m/s]. Fuels remaining is 6.7 percent, oxidizer of 9.2 percent. My PUGS is reading Off-scale High on the increase. I put through the procedure but apparently it did no good at all. I'm still reading full scale increase on the PUGS and my oxidizer flow valve is still in Increase at the completion of the burn.

137:47:41 Engle: Roger, 10. We copied all of that.

137:48:15 Engle: 10, this is Houston. We'd like to go ahead and take that fuel cell 1 off both buses now.

[MCC-H are anxious to get the ailing fuel cell 1 off the line to preserve it for future use during any midcourse corrections.]

137:48:23 Cernan: It's going off right now, Joe.

137:48:58 Cernan: Houston, the TV is being turned on now, and as Tom is starting to pan we have a couple of quick short words for you.

137:49:06 Engle: Roger. We're standing by. Go ahead.

137:49:07 Spacecraft: (Music: "Going Back to Houston" by Dean Martin)



(Click on the above image for a larger version.)

137:49:31 Engle: Roger, 10. This is Houston. We copied that transmission. Thank you.

137:49:37 Cernan: Glad you got the message.

137:49:51 Young: Boy, this view's got to be a fantastic thing.

137:50:03 Stafford: Houston, 10. I hope the Aussies have their sets tuned in because it's utterly fantastic here.



(Click on the above image for a larger version.)

137:50:08 Engle: Roger that, Tom. I'm sure they're all watching.

137:50:26 Young: We are taking a picture right now of Tsiolkovsky down south there. That's impressive.

[The receding Moon is filmed using 16-mm magazine W.]

16-mm DAC Mag W. Download magazine.

Click on the above image for the complete sequence.

[The shot of the receding Moon is at 00:56 into the magazine. The large far-side crater, Tsiolkovsky, stands out owing to its dark, mare-like floor and prominent central peak. Unline the lunar near side, the far side has very little mare surface.]

137:50:35 Engle: Roger. Copy.



(Click on the above image for a larger version.)

137:50:36 Young: What a place.

137:50:51 PAO: And we have a black and white signal at this point.

Still image from Post TEI TV coverage

TV coverage from 137:51:00.

(Watch video file by clicking above image, or right-click to download.)

137:51:00 Young: Joe, that's Tsiolkovsky back there. It's big and black and very distinguishable. Fantastic! Incredible!

137:51:11 Engle: Rog. We can see it pretty plain on the set. That's the one right up near the horizon. Is that affirm?

137:51:18 Young: It's sitting on the horizon; way out there. Right.

137:51:26 Engle: Hey, there you go. Now we're picking it up. We can see the center of it now.

137:51:29 Young: We can see the whole of the Smyth's Sea now.


AS10-27-3915 showing Mare Smythii. This image is inverted. North is to the lower left corner.

(Click on the above image for a larger version.)

137:51:32 Cernan: That's it, Joe. That's full zoom. You ought to be able to see that real good.

[The camera is zoomed in on Tsiolkovsky, its bright central peak distinct against the surrounding mare material that covers its floor.]

137:51:36 Engle: We can. That's just real good, Gene.

137:51:38 Young: I can see the whole of the Smyth's Sea and I see old F-1 down there.

137:51:54 Cernan: There's Neper.

137:52:04 Young: Got this big bright ray crater up on the northern horizon. They are going to try and put that on the tube. Boy, that's a big one. The rays of Schmidt Crater go all the way across the Moon.

137:52:28 Young: Must be new.


AS10-27-3920 showing Mare Crisium and the bright rayed crater Proclus.

(Click on the above image for a larger version.)

137:52:32 Engle: What's your f-stop setting on the camera now?

137:52:40 Stafford: Roger, Joe. I've got it at 22. The Moon's awful bright.

137:52:43 Engle: Roger that, Tom. Thanks.

137:52:50 Stafford: I'll occasionally flick it up, down, and then back to help saturate the tube, but that's what you see, there. OK. We're taking all kinds of pictures. I've got the tubes, Gene-o has the sequence camera, and John has the Hasselblad. We're getting all this documented.


AS10-27-3924 again showing Mare Crisium and Crater Proclus.

(Click on the above image for a larger version.)

137:53:21 Stafford: Is that better, Joe?

137:53:24 Engle: Yes. That's a little better there, Tom. What did you do there?

137:53:41 Stafford: Stand by. I'll change my ALC switch on it.

[ALC is variously thought to stand for Automatic Light Compensation, or, more likely, Automatic Level Control. Essentially, it is a circuit in the camera that senses the signal coming from the vidicon sensor, and adjusts the gain of its internal amplifiers to maintain a viable output image across a range of illumination.]

137:53:58 Engle: Yes. That's a little better, Tom. That's great, The detail is coming out a lot better.

137:54:06 Stafford: OK. Again, as we move away, the basic Moon looks tan to us. The new craters are definitely white from the impact and some of the volcanic ones; but from this Sun angle, it's basically tan out there - a white, white tan. And the rays you can see are even whiter. And moving over this way, the one crater you can see over there is a brownish in color with the one central peak in it. I'll try to put the zoom on it for you.

[Tom has zoomed back onto Tsiolkovsky.]

137:54:55 Engle: Roger, Tom. We're picking it up now. We can see the central peak in the crater.


AS10-27-3926 showing Mare Crisium, Fecunditatis and Tranquillitatis. Crater Langrenus can be see at lower right.

(Click on the above image for a larger version.)

137:55:02 Stafford: OK. Do you have any color there, Joe, at all?

137:55:06 Engle: Say again, Tom, please.

137:55:09 Stafford: Roger. Do you have color in Houston, or just black and white? Over.

137:55:13 Engle: We got color here in Houston. There's quite a bit of light for the color, although we can make out the crater and we can see the central peak in it. The black and white is coming out real good.

137:55:25 Stafford: OK.

137:55:30 Stafford: OK. What I'm looking at now is a brown, and the peak in it is light tan - around it is a little darker tan. Does that correlate with your colors? Over.

137:55:45 Engle: Roger. That looks real good on the monitor here, Tom. That's just what we're seeing here.

137:55:52 Young: This is absolutely incredible!

137:55:58 Stafford: I thought it was a fantastic view leaving the Earth, but it is going to be even more fantastic one leaving the Moon here and heading back to the good old Earth.

137:56:04 Engle: Roger that, Tom.

137:56:14 Young: I got the whole of the Smyth's Sea. [Garble] Crisium.

137:56:18 Engle: Roger.

137:56:23 Stafford: OK. The way you're seeing it right now is about f:50, pardon me, 55 [mm] on the zoom. That's about the way we're seeing it now, maybe a little more.

137:56:34 Engle: Roger. Understand.

Air-to-ground audio

137:57:01 Stafford: OK. I'll hand the camera over to John here and he'll show you the Sea of Crises. Over.

137:57:09 Engle: Roger. And while you're doing that, Tom, we got confirmation on your burn. It looks like we'll have about 1 foot per second [0.3 m/s] at your first MCC at 15 hours.

137:57:21 Stafford: Roger. I think we can afford about 1 foot per second [0.3 m/sec]. That isn't bad.

137:57:29 Engle: Can't hardly beat that.

137:57:35 Stafford: Yeah. The old guidance system is doing great work for us on this mission.

137:57:40 Engle: Roger that. That's a real interesting picture that you're showing us now, too.

[View from window 2. The dark areas are east of Mare Crisium and for Mare Undarum.]

137:57:41 Stafford: [Garble]. Tell the people responsible for it that it works just fantastic [garble].

137:57:54 Stafford: And also for the first time, we're seeing what we call I guess, what Gene just termed a gigantic turtle-backed crater that's fractured. We'll put the zoom on that in just a minute.

137:58:03 Engle: Roger.

137:58:04 Cernan: There's a real interesting crater here on my right, Joe. It's an enormous thing and it's fractured almost symmetrically in a number of pie-shaped pieces. Let's see if we can get it for you in a minute.

[Cernan is describing the crater Humboldt.]

137:58:16 Engle: OK. We're standing by.


AS10-27-3930 showing Langrenus, Mare Fecunditatis and in the upper left corner, Humboldt.

(Click on the above image for a larger version.)

137:58:27 Stafford: In fact, looking straight ahead, just now coming into view, even though we're really starting to climb out from it - In fact, I can finally see the whole Moon right in the hatch window. But looking down the road, there's Messier A and B, the Taruntius twins. We have Censorinus there for Jack. And on up ahead I can see Landing Site 1 even from this distance from the landmarks that led in. Over.


AS10-27-3932 The Messier craters with their double ray pattern along with the Taruntius twin craters in northern Mare Fecunditatis.

(Click on the above image for a larger version.)

137:58:47 Engle: Roger. Understand. That's real good to know.

137:58:53 Stafford: Boy, you can't believe this rate of climb. It looks like we're just going out just vertically. Just beautiful. It would scare the heck out of you if you came at this angle, but maybe it was just because we came in the dark and didn't see the thing. Over.

[Humboldt is centred in the camera, its dark patches just inside the rim showing up distinctively. The Sun's illumination is at quite a high angle so topography is difficult to make out. In these conditions, albedo differences are more prominent.]

137:59:12 Engle: Roger. Understand.

137:59:16 Cernan: Hey, Joe, that's that crater I was talking about. I don't know how that is, but I can see a little bit of it in my monitor.

137:59:23 Engle: It's coming in real good, Gene. It looks like you're just about to crowd the top part of the window there, but we’ve got the whole crater, and yeah, we can see those fractures in there.

137:59:35 Stafford: It looks like the outer rim is slumped down and you have some maria material near the edges and the whole thing is fractured there in the middle from a couple of impacts near the center.

137:59:43 Engle: Roger. We can make it out.

137:59:50 PAO: Spacecraft now some 850 nautical miles [1,574 km] from the Moon.

137:59:53 Stafford: OK. Down in the central part here, it's still a tan color and as we move further away, it's starting to get a little more white in the mare areas, turning to a light brown - a whitish brown. Over.

Flight plan

138:00:06 Engle: Roger. Understand.

138:00:07 Cernan: Kind of looks like the real Moon.

138:00:11 Engle: Roger. The crater that you were show...

138:00:13 Cernan: It's a little rounder, too, isn't it? Go ahead, Joe.

138:00:16 Engle: Rog, Gene. I was just going to say that that crater you were showing us, your fractured crater there, it looked like there was a dark patch on the left-hand side. I wonder if that was just something that showed up on the tube or if you observed that up there. In the upper left-hand corner there now.

[Engle is referring to Humboldt. This 207-km crater near the Moon's limb is notable for having a series of rilles on its floor (a fractured-floor crater) and dark areas of mare-like surface, probably volcanic.]

138:00:35 Stafford: No, Joe. That looks like maria material. That's right, that's maria material in that crater, Joe. Over.

138:00:45 Engle: Rog. That's real interesting.

138:00:51 Stafford: Just wait till about another 30 minutes. Bet you'll be able to see the whole thing, then. Over.

138:01:05 Young: That engine did it again, boy. What a prince.

138:01:08 Cernan: Does it look a little rounder?

138:01:11 Engle: Rog. Looking real round now. If one of you guys get half a chance, see if could give us Accept on the computer, we'll shoot you up a new load.

138:01:22 Stafford: That sounds good. We're in P00 and Accept. You got it.

138:01:25 Engle: Roger. Thank you.

138:01:26 PAO: Altitude 930 [nautical miles, 1,722 km].

138:01:28 Engle: Man, it looks like you guys are climbing out of there.

138:01:34 Stafford: Rog. You'd better believe we're climbing out, just like we're in a vertical climb going straight out from the center: it's a fantastic sight. Also for the record, I was just looking here. It's a beautiful beach but where's the ocean? Over.

138:01:50 Engle: Rog. (Laughter)

138:02:15 Stafford: OK. I’ve got the camera back in the central window again.

138:02:36 Cernan: Joe, this is incredible. That thing is getting rounder and rounder and rounder and smaller all the time.

138:02:40 Engle: Rog, Gene-o. Understand.

138:02:46 Cernan: The real show is on the inside here; it's like three monkeys in a string pod.

138:02:51 Engle: Yes, I'll bet that’s right.

138:02:53 Stafford: Joe, I’ll tell you, what you see out there is real close to what we have; maybe the curvature is a little more. Now one thing real interesting, you see the two dark spots there in the center of your screen, the maria material. Over.

[The two dark spots referred to by Stafford are Mare Marginis on the left and Mare Smythii on the right.]



(Click on the above image for a larger version.)

138:03:03 Engle: I’ve got them.

138:03:05 Stafford: OK. Now to us, and all three of us have correlated this, that is a light brown color and surrounding it you have the highland areas there which is a tan color, and you can see that one impact spray crater up there that's a white chalky color. Again, that looks just like the material of gypsum, I'd say. Over.

138:03:25 Engle: Rog. We’re getting the same colors that you are describing, Tom. It's just great, fantastic!

138:03:38 Stafford: OK. I've got another crater over here I'll zoom in on. It is to the right of that one maria, and you can see it: it's real bright with rays coming out of it, and I'll zoom on it.

[Stafford zooms in on a bright ray crater on the northeast rim of the crater Gibbs.]

138:03:48 Engle: Roger.

138:03:52 PAO: Apollo 10 now 1,060 [nautical] miles [1,963 km] from the Moon.

138:04:03 Engle: OK, 10. This is Houston. You can go back to Block on the computer. It's yours and the fuel cells are looking real good and you might he interested to know you are coming in real great all the way across Australia.

[Now that fuel cell 1 has been taken off the buses, MCC-H are confirming that the remaining two fuel cells are handling the current load satisfactorily.]

138:04:18 Stafford: Well, to the people of Australia from the crew of Apollo 10, we'd like to say good morning. We've seen your country many times on the way up to the Moon, and we'll see it many times on the way back. It looks very beautiful from even 210,000 miles [390,000 km] out. Over.

138:04:42 Cernan: [Attempting an Australian accent] That Tommy is a charmer.

138:04:45 Engle: I should say.

138:04:49 Cernan: Hey, Joe, the Moon is almost small enough now where I can see the whole thing from the top, one corner of my forward window to the other corner of my forward window.

138:05:00 Engle: Roger. Understand.

138:05:02 Cernan: I can see the whole Moon from top to bottom in my forward window.

138:05:05 Engle: Roger. Understand, Gene.

138:05:14 Stafford: Looks like the old camera is doing a pretty good job here, zooming in and out picking up spots.

138:05:32 Engle: You guys are really hauling the mail out there.

138:05:37 Stafford: Boy, you better believe it. It's like we're climbing straight out, Joe. It's a fantastic sight: it’s like we were shot straight out from the center of the Moon.

138:05:46 Cernan: Is that what you call it, Joe?

138:05:49 Engle: That's what we call it tonight. You're going about 6,000 feet a second [1,830 m/s].

138:06:03 Stafford: OK. We're picking up now more of the maria material and, again, even from this distance still, to keep the recording going, it is a brown in the maria area; the surrounding area is a light tan; In fact, I've got one little crater I'm going to try to zoom on. See the maria area on the left side of your screen now? Over.

138:06:20 Engle: Roger. Got it.

138:06:24 Stafford: OK. Up in there is a little rather small maria area of round spray crater. Let's see if we can zoom on that spray crater there.

[Stafford is referring to Mare Crisium.]

138:06:32 Engle: Roger. OK.

138:06:42 Cernan: Joe, that fractured crater that had the dark material off on the left side is also about one-fourth of the bottom right-hand side. You're not looking at it now, the bottom quarter of the right-hand side - It's all full of that very darkish - dark gray material, also.

138:06:57 Engle: Roger. Copy, Gene.

138:06:58 Stafford: In fact, right now all the people watching TV are at an advantage because what you're seeing in your screen is a bigger image than what we see. And right there, see that little white crater that I put down there about the center of the screen?

[The bright rayed crater is Ellmart A on the NE rim of Mare Crisium.]

138:07:10 Engle: Roger. We got it.

138:07:12 Stafford: The white chalky material is surrounded - you have some tan, and then around the base maria over here on the right, and that is brown. Over.

138:07:22 Engle: Roger. Thank you, Tom. That maria over on the lower right...

138:07:27 Stafford: No. Hold on.

138:07:28 Engle: Is that dark brown, or is that black?

138:07:33 Stafford: No, no. The maria here that is right in the middle of the screen. Now, Joe, that is a brownish color. We estimate a light brownish color with slight streaks of tan that are over from the right crater. But this one is coming up right here. I'll put the zoom on it. Do you see that rascal?

[The 'rascal' is the crater Proclus, a very prominent ray crater to the west of Mare Crisium. It is 28 km in diameter and is notable for having a distinct excluded zone to its ray system on its west side, a result of the very oblique impact that created it.]

138:07:48 Engle: Roger. We got it.

138:07:49 Stafford: OK. The crater that you have now: the inside of that is chalky color; the rays coming out are light tan; a darker tan surrounds it, and then you move into the maria which is a brown color. Over.

138:08:03 Engle: OK. We got all that description. Boy, that little crater with the grays sure stands out nice.

138:08:11 Stafford: Right. And you can see down into it, and the sides are just a chalky white color; at the bottom is a tan like we've seen before, surrounding it is a white tan with the rays lighter. But going over to the maria, you can see the rays in the maria material there, a light tan over a brown. Over.

138:08:28 Engle: Roger. We understand.

[Apollo 15 orbited directly over Mare Crisium at a low altitude two years later and Dave Scott described how the rays from Proclus that lay over the mare had the appearance of a mist. They are actually pulverised and shattered rock thrown out from the impact.]

138:08:33 Cernan: Hey, Joe, down at 9 miles [16.7 km] has to be exciting, but this has got to be unbelievable. The wind - the Moon now is well within the boundaries of my forward rendezvous window.

138:08:45 Stafford: And now that we're showing you that crater, just one thing I wanted to check - Does our description of the color match with your picture down there? Over.

138:08:52 Engle: Right. It's coming up pretty good, Tom. The area - maria area that you described as brown looks a very dark brown here, almost black, a real dark brown, and evidently, that's a little lighter to you than it shows up on the screen.

138:09:07 Stafford: Yeah. OK. What about the tans? Is that somewhat about the same? Over.

138:09:12 Engle: Roger. That's looking real good. In fact, Tom, I'm at a little disadvantage. I'm looking at the big screen up here on the board, and they say on the monitor in the back of the room there, that the colors are exactly as you're describing them.

138:09:26 Stafford: OK. Well, I passed my eye test I guess the last time for the T minus 4-day physical so I guess they haven't gone too bad. This is an interesting crater right here; looks like a lot of them formed after you have a big crater, then you have slumping in the walls. Here you can see a series of ridges where the walls are slumped down in, and I'll zoom in a little bit. Over.

[Stafford has now panned south from Mare Crisium to the crater Langrenus.]

138:09:48 Engle: Rog.

138:09:55 Stafford: OK. And the whole view now is getting so fantastic I'm going to go out to the wide angle to show you what we're seeing. I can see the whole Moon right out the hatch window.

138:10:03 Engle: Roger.

138:10:09 PAO: That view from 1,400 [nautical] miles [2,600 km]...

138:10:13 Engle: Oh, that’s beautiful.

138:10:17 Stafford: Well, there it is.

Air-to-ground audio

138:10:21 Cernan: See what I mean about size, Joe. It just about fills up, roundwise, right smack in the hatch window. Boy, and is this a full Moon, I'll tell you.

138:10:39 Engle: You're just about 1,400 [nautical] miles [2,600 km] out now, Gene.

138:10:44 Stafford: Roger. 1,400 [nautical] miles [2,600 km] out from the Moon, and the view is actually just incredible like Gene has described. We're all just laughing up here. Just looking at it. Again, as we've said before, it's a good thing we came in backwards at nighttime where we couldn't see it because if we came in from this angle you'd really have to shut your eyes. Over.

138:11:06 Engle: Rog. Understand. Tom, how about going to the other position on ALC [Automatic Level Control] and let's see how it looks.

138:11:19 Stafford: There's the other position. [Pause.] Joe, we've been shooting this whole thing at f:22.

138:11:31 Engle: Rog. Understand. Okay. That's good, Tom. Go on back to - let's see, I imagine you're on...

138:11:36 Stafford: We're going back to...

138:11:42 Cernan: We're on the outside now, Joe. How's that? That's where we were. We just went inside for a while and then came back.

138:11:47 Engle: Roger. That's a lot better. Stay on the outside.

138:11:54 Stafford: And, again, this whole area looks - That maria material is brownish and still the color hasn't changed much. It's brown and tan with lights. Over.

138:12:13 Young: Hey, Joe, with a midcourse of a foot a second [0.3 m/s] we must be in that corridor.

138:12:19 Engle: That’s pretty close.

138:12:24 Young: Boy, that's absolutely incredible targeting down there. Congratulations.

138:12:29 Engle: You can almost begin to start smiling, can't you?

138:12:31 Young: To the boys in the back room. Yeah.

138:12:37 Stafford: I’ll bet Phil Shaffer has a smile across his face if he's around. Over.

138:12:47 Engle: Yes. He's in a room down the hall. But I'm sure he's grinning.

138:12:48 Young: Tell him to have one on me.

138:12:50 Engle: Roger. Will do.

138:12:52 Cernan: How come all you people are up? How come all you people are up this early in the morning?

138:13:01 Engle: That's normal working hours, Gene-o.

138:13:08 Stafford: I will try to pick you out a couple more interesting characteristics. Again, you can see that one sprayed crater up to the side. Actually, here's a better view, I can see the landing site coming in now, and we'll go down and take a look at Messier, Messier B, the Taruntius twins; we can see it from here. We'll put the zoom to them.

138:13:34 Cernan: You can walk right up the landing site just like we did when we were down there. You can see Secchi; you can see the Apollo Ridge; you can see all those little ridges reflected very well in sunlight. You can't quite see our Sidewinder or Diamondback Ridge at this time, however.

138:13:52 Engle: OK. We understand. Yeah, that little crater that you're bringing into focus, bringing in the zoom now, with the rays, that's a real interesting little feature in it.

138:14:06 Stafford: Yeah. Would you ask Jack Schmitt, please ask him what the name of that crater is, just for identification? I think we may nave seen that before. Over. And it's Censorinus A.

[The bright ray crater in the field of view is in fact again Proclus.]

138:14:22 Engle: I think, I think you got a "got you" on Jack Schmitt. He's grimacing and his head is furrowing now, but he'll have a name for you here in a minute.

138:14:34 Stafford: OK.

138:14:56 Cernan: Jack, since we didn't get any pictures of Censorinus, we thought we'd zoom in on it from here.

138:15:00 Engle: Roger, Jack says the name of that one is temporarily Tom's Crater.

138:15:11 Stafford: That sounds good. OK. And right ahead from the bright crater as you walk on across there, you can see Moltke. There's Moltke, and right up in there, if anybody from Oklahoma's listening, that's what we've termed the Oklahoma Hills. It's on the right. Over.

[Stafford has zoomed in slightly on Mare Tranquillitatis.]

138:15:31 Engle: Roger. We got those, Tom.

138:15:38 Stafford: In fact, this camera's got such good resolution I think I can even zoom on Moltke from here.

138:15:44 Engle: OK. We'll stand by.

138:15:50 Stafford: Can you see the bright crater in the center of the screen there?

138:15:53 Engle: Roger. We got it.

138:15:57 Stafford: That is Moltke. The Landing Site 1 is right to your left there. At least, it's in my monitor. So here we can see Landing Site 1. In fact, we can even see crater 130 in this tube. And all the white area which would probably be the tan area. It's white in my black and white - It's white in my black and white tube, but it's brown and tan out there as you look there. That's what we call the Oklahoma Hills. Over.

[Moltke is in fact the small isolated crater towards the right of the screen.]

138:16:20 Engle: Roger, Tom. We've got it. It looks great. That's too bad that you all don't have color TV up there. This is a great view.

138:16:30 Stafford: Yes. OK. I brought the zoom back again. That maria material is really looking a deeper brown, now.

138:16:37 Engle: Roger. OK.

138:16:38 Cernan: Hey, Joe, we're starting to see the terminator come in, I believe. We're starting to see the terminator come in on the far side which is really getting to be interesting. And we might say we're real thankful for it too.


AS10-35-5243 starting to show the terminator.

(Click on the above image for a larger version.)

138:16:52 Engle: Rog. Understand.

138:17:07 Stafford: We're going to show you a picture of the far side of the terminator in just a few minutes. One thing I'd like to point out if I could back on Messier. Those two sprayed craters, and I've made some drawings of them to bring back as to what it does - Leave it here, I'm going to zoom on them.

138:17:24 Engle: OK.

138:17:56 Young: Well, we've got a lot of pictures to bring back and I'm sure they'll be very interesting to you, but I'm afraid they're going to ask as many questions as they answer.

138:18:06 Stafford: OK. If you look in the center of your screen you see two vertical craters. You got them? And you have the sprayed rays that come out down this way. Do you see those? Over.

138:18:14 Engle: Roger. We got it, Tom.

138:18:18 Stafford: OK. That's the Messier Craters and from here again you can see the maria material. It is a brown and the inside of the crater is a light tan and the rays that are sprayed out of them. As you can see, there are just two rays pronged out of it. Out over the highland area it goes up to Censorinus, and those are tan rays that come out over the darker material. Now we're getting to see some of the back side, some rilles, some of the rugged side. We'll go down in this area.

138:18:48 Engle: Roger.

138:18:50 Stafford: OK. I guess it can be, if you're upside down, it could be front side or back side.

[Mare Nectaris is now in the center of the field of view. The sunrise terminator is just coming into view.]

138:18:58 Engle: OK.

138:18:59 Cernan: The shadows are really lengthening and - The shadows are really lengthening in the terminator area and you can definitely see the terminator approaching.

138:19:11 Engle: Rog. We can see it on our screen here, Gene-o.

138:19:26 Young: I think what it is, is we're approaching it.

138:19:33 Engle: Good call, John.


AS10-35-5244 showing the terminator becoming more apparent.

(Click on the above image for a larger version.)

138:19:34 Stafford: One thing that we were real happy to see around - Rog. One thing that we're all happy to see around the Moon was some nighttime, because from the time we made TLI until we arrived at the Moon it was strictly out there in daytime all the time. It's really a pleasant change to get back for a little nighttime. Over.

138:19:49 Engle: Rog. Understand.

138:20:08 Cernan: Joe, it's still incredible. It almost doesn't look real. This Moon is set against a blackest black, incredibly black, that you can ever imagine.

138:20:19 Engle: Rog, Understand.

138:20:21 Stafford: The black has about the texture that you see often times that comes out of an oil smoke fire. It's really a - It's a jet black.

138:20:31 Engle: Roger. Copy. And you're about 2,000 miles [3,700 km] out now, 10.

138:20:38 Stafford: Rog. Understand 2,000 miles [3,700 km] out.

138:20:41 Cernan: I never thought anything could be as enjoyable as this, even with the fuel cell light on.

138:20:47 Engle: Rog.

138:21:15 Stafford: Okay. Again, here's a real good size crater with patterns. I'll zoom in on it.

138:21:23 Engle: Roger.

138:21:34 Engle: Roger. We can pick it up now and we're picking up the rays, Tom.

[Once again the TV is zoomed in on the crater Proclus, its distinctive partial ray system proving to be attractive to Tom as he operates the camera.]

138:21:42 Stafford: OK. As you look at that crater, again, the bottom floor of it is tan. You can see some slumping on the walls; the sites are chalky white; the rays going out are light tan; the area surrounding it is a darker tan, and then you move over to the maria area which is a darker brown than up here. But the crater is really a beautiful crater. It stands out with all those rays on it.

138:22:07 Stafford: And down below, you can see the remains of an old crater still in the maria material. Try to put it right in the center of your screen and it is right at the edge where the mare starts. Can you see it? Over.

[Now centered is the crater Lyell.]

138:22:16 Engle: Roger. We got it. And it looks like there's another one on over to the left and down a little bit, another old crater with some maria in the middle. It may be shadows.

138:22:24 Stafford: Sure is. Right there.

138:22:29 Slayton: What color did you say that was, Tom?

138:22:33 Stafford: Say again. Over.

138:22:38 Slayton: What color did you say that was?

138:22:40 Stafford: Oh, is that our Guidance Officer? Roger. If that was Phil Shaffer talking, just tell him that he's got a bottle of champagne due him for that vector. Over.

138:22:52 Engle: That was Deke. He was wondering - verify the color of that maria.

138:22:56 Stafford: OK. I know what he's talking about but I'll - We'll talk about that later.

138:23:08 Cernan: He's got one coming for not passing up any PADs while were gone from John.

138:23:15 Cernan: Hey, I bet we fooled old Snoopy.

138:23:19 Engle: Rog.

138:23:21 Stafford: OK, Houston. I've got an interesting sight like we've never seen. Houston, take a look at this. We've never seen this before. The varied colors. You see the two mare areas on the left.

138:23:30 Engle: Roger. Got them.

138:23:32 Stafford: Well, the one right - They're different shades. The one right in the center is a darker brown than the one over to the left. You can see where they've flowed together there. It is a lighter brown, tending to a tan. I'll put the zoom on and hope you can get it. Here it is. We've never seen this before ourselves.

[Stafford is describing the tonal differences between Mare Serenitatis and Mare Tranquillitatis. The basalts that form these maria are, indeed, of differing colour and this reflects their slightly different compositions. Serenitatis basalts are richer in magnesium and iron and display a very slightly reddish or warm colour, especially towards the centre. Tranquillitatis basalts are richer in titanium and exhibit a distinctly bluish hue.]

138:23:51 Engle: OK. It's showing up pretty good right now, the way you're describing it. There you go. It looks great.

138:24:00 Young: Looks like a couple of different flows there.

138:24:03 Stafford: Right in the center of your screen you should see the discontinuity between the two maria areas. The one on the right is a darker brown, nearly a chocolate brown now, and the one on the left is a tan. Over.

[Stafford has zoomed in and centered the field of view on the area adjacent to the crater Plinius. This is the area where the tonal differences between Mare Serenitatis and Mare Transquillitatis are most conspicuous. Mare Tranquillitatis is darker than the central fill of Mare Serenitatis.]

138:24:16 Engle: Roger. That's just how they're coming in down here, Tom.

138:24:23 Stafford: Rog. Great. Hey, if you look over in the distance, you can see the nighttime coming on the Moon up near the terminator and you do get some outstanding features there.


AS10-35-5245 showing the terminator becoming more apparent.

(Click on the above image for a larger version.)

138:24:34 Engle: Roger. We've got that.

138:24:35 Stafford: That's the first time we've been able to look at this distance and see a real discernible difference in the maria materials. But this is really kind of a classic, I think the - You can see the flows, and also if you take a look, I'll try to zoom some more - the maria on the left, you can see some of the darker material near the upper edge of that where it's flowing in there.

[Coincidentally, Stafford has now zoomed in on the area in the south east corner of Mare Serenitatis, which includes the valley of Taurus Littrow, where Cernan will land during Apollo 17.]

138:24:53 Engle: Roger.

138:25:32 Stafford: OK. That's the picture we have now. You can see we probably are well on our way out close to 3,000 miles [5,550 km] now. It's still a beautiful view. In fact, just looking at it, you recollect that we've come a long ways in a few years, so just imagine where we’re going to go in a few more years. Over.

138:25:48 Engle: Roger that, Tom.

138:26:06 Stafford: Again, I just want to check the resolution of this camera and zoom in on Censorinus, and the landing site where Apollo 11 will land, and I’ll go back and zoom in on that again. Over.

138:26:16 Engle: Roger.

138:26:27 Stafford: OK. There is Censorinus. Over here is the crater Moltke, above Maskelyne, Maskelyne B. We come down here to Little Bright Crater there. It's right near the dip of the Oklahoma foothills there. It's called Moltke, and to the left, right in this area, is the landing site where Apollo 11 should land. Over.

[Censorinus is the small very bright crater towards the center top of the field of view.]

138:26:45 Engle: OK. We got them all, Tom. They are coming through real good.

138:26:50 Young: Boy, right now, it's like watching it through a telescope. It's fantastic.

138:26:57 Stafford: Right in the center of your screen is the landing site. Again you can see the hills on the other side down in this area. But the approach is very well marked by Censorinus there on one side and the lead in there from the two Maskelyne craters. Over.

138:27:10 Engle: Roger. We're getting real good resolution down here, Tom.

138:27:18 Stafford: OK.

138:27:32 Stafford: I guess we've been up nearly 24 hours now, but it feels so great, I don't think we will go to sleep for a few more hours. Over.

138:27:38 Engle: OK. Understand, Tom.

138:27:47 Stafford: Just looking at this is about the best go pill you could ever stand. Over.

138:27:52 Engle: Roger.

138:28:10 Cernan: Tom's going to try and zoom in on Langrenus for you. It's a pretty interesting crater; it's in the sunlight at the moment.

[The vidicon-type electron tube sensor on the TV camera exhibits a large degree of image lag. An effect of this is that the television pictures only really get to display their full resolution when the image is kept stable. Unfortunately, Tom is hand-holding the camera in zero-g and has difficulty keeping it still when its lens is zoomed in.]

138:28:25 Stafford: OK. What you have there is the crater Langrenus, and again, that is somewhat on the path that leads up to the Apollo Landing Site number 2. It comes right down this way. There you have the – other craters, and, there is Messier, comes on down across – In fact, there is the crater Weatherford and Mount Marilyn, down to Censorinus and comes right on over into Moltke and the landing site.

138:28:53 Engle: Rog. Very good tour.

138:29:01 Cernan: Yeah. John sort of explained it here a second ago for us all. He said he can't believe what he is seeing, and we really can't. We just can't believe what we're seeing. I tell you, Joe, this satellite of ours, this Moon of ours, had a rough beginning somewhere back there. Over.

138:29:15 Engle: Rog. Understand, Gene.

138:29:16 Stafford: It's really a privilege to sit - it's really a great privilege to just sit here and, as the spacecraft moves radially outward and look at it, to feel - just to share some of our views here with you. Over.

138:29:30 Engle: Copy that. Thank you.

138:29:44 Cernan: The important thing about that camera, Joe, is what you're seeing is happening and what you haven't seen ain't happened yet.

138:29:53 Engle: Roger.

138:39:05 Stafford: All three of us are commenting again that for the scientific interest, about the difference in color on that one maria area I pointed out to you there as soon as I saw it, and it's really becoming pronounced now. The basic maria area - I'm going to zoom in again – is like a chocolate brown, and from this Sun angle and over to the left is like a tannish brown. And again I’ll zoom in and just see how it looks to you. Over.

[Stafford has zoomed in back to the meeting of Mare Serenitatis and Mare Transquillitatis to show their colour differences.]

138:30:44 Stafford: OK. There you are. I hope the colors come out the same to you, the same as we see them here. You can see the discontinuity there By those two craters. Over.

138:30:52 Engle: Roger. It looks great, Tom: just like you're describing it.

138:30:59 Stafford: OK. Thank you.

138:31:13 Stafford: OK, Houston. This is Apollo 10. All three of us are commenting again about this fantastic view out here and how it's probably just as well that we approached this thing in night side where you can't see it, because if we approached at this angle coming in, you would really have to shut your eyes. Over.

138:31:29 Engle: Rog. Understand.

138:31:34 Cernan: Hey now, I wasn't skeptical when we were coming in. I just said I'd believe all that targeting when I saw 60 miles [111 km], and I'm a believer, and you've got one on me. But boy, I tell you if we were going forward now it would be a different story.

138:31:48 Engle: Roger.

138:31:52 Young: Along that line, I want to congratulate you on that 5-degree window mark. It was perfect.

138:32:02 Engle: OK. We copy.

Air-to-ground audio

138:32:45 PAO: Apollo 10 now 2,700 [nautical] miles [5,000 km] from the Moon.

138:33:55 Stafford: Houston, Apollo 10. You know you've often heard of the nursery rhyme about the man in the Moon. We didn't see one there, there were three men around the Moon and pretty soon we hope that there are three men - pardon me, two men on the Moon and one circling. But as far as seeing a man in the Moon directly, we just didn't see it this time. Over.

138:34:13 Engle: OK, Tom. Thank you.

138:34:18 Cernan: And we were looking, too.

138:34:20 Engle: Roger.

138:34:23 Young: If there were any people down there, they had a lot of rocks to play with.

138:34:32 Cernan: It won't be long now until Snoopy’s descent stage will be there with a big red, white, and blue American flag on it, though.

138:34:39 Engle: Roger that.

138:35:10 Stafford: Houston, for just a quick break here we want to be able to show you that we're slowing down now as we leave the Moon. You've seen a fantastic sight. We want to just take you inside the cockpit and say hello for a minute, and then when we come back out you should be able to see the - to really get a better view of the Moon there with respect to having a whole sphere. Over.

138:35:35 Engle: OK. Mighty fine. We're standing by, Tom.

138:36:41 Engle: OK. Your picture is coming in real good, real clear.

138:36:47 Young: Hello, everybody.

138:36:51 Stafford: While the view outside is fantastic, inside here, we look like about three scroungy characters, but we really feel great, and it's been a fantastic trip. Over.

138:37:02 Engle: Roger, Tom.

138:37:07 Engle: You guys looking mighty good in there.

138:37:12 Stafford: Roger. You getting any color on us in here?

138:37:14 Engle: Roger. The color is real good inside.

138:37:20 Stafford: Well, we feel great, and we've felt great ever since lift-off, and it's been a fantastic voyage. In just a minute we'll turn the camera around and show you John. Over

138:37:36 Engle: Roger. Who is winning the beard-growing contest in there?

138:37:44 Stafford: Well, I don't know. John's got the mustache won. I don't knew about the beard.

138:37:50 Cernan: I'm the baby of the group, Joe.

138:37:54 Engle: OK.

138:37:56 Stafford: OK. We'll show you John.

138:38:04 Cernan: John's got a little blue ink on his fingers.

138:38:09 Young: I was writing a letter and I broke my pen. Does it show up in living color?

138:38:17 Engle: Open your hand up again.

138:38:23 Engle: Yes. It sure does.

138:38:29 Young: How about that.

138:38:42 Young: You can see we're pretty happy about this whole business.

138:38:47 Engle: Roger that. It sure looks good to see you again.

138:38:54 Cernan: What are you doing?

138:38:57 Engle: We got your message on the blue dye, John.

138:39:03 Stafford: Roger. You've got to watch when you write a lot with blue pens, and we're going to take you back outside and show you the Moon as we see it. Over.

138:39:37 PAO: And we have a view from 3,000 [nautical] miles [5,550 km].

138:40:04 Cernan: Joe, the Moon is starting to lose its spherical shape. It's becoming oblong now with the terminator, with us going around into the area of the terminator.

138:40:15 Engle: Roger. We are showing that on our screens down here.

138:40:26 Cernan: You know, looking at the Earth terminator and the Moon terminator is the only way we can figure out which is up and which is down, and sometimes they don't agree.

138:40:36 Engle: Roger.

138:40:37 Young: For you people who aren't in the space flight business, I say it sure is fantastic and you really ought to try it.

138:40:47 Engle: Thank you, John. I hope to some day.

[After missing out on Apollo 17 due to being substituted by Jack Schmitt, Joe Engle did eventually fly in space twice, commanding Space Shuttle Columbia on STS-2, and Discovery on the program's twentieth flight (51-I).]

138:40:49 Stafford: This is Apollo 10. It appears that the tube - Roger, Joe. Houston, it appears that the tube is starting to saturate when I go to full zoom and then it's gathering in too much light and it's coming back normal from the Sun's rays. Are you getting that on your screen? Over.

138:41:08 Engle: No. We're still getting a real good picture down here. Tom.

138:41:18 Stafford: OK. I'll go back to the full zoom and just hold it there for a little bit.

138:41:28 Cernan: Joe, I've always believed that nothing is impossible, and now I'm convinced of it, and I hope that what we are doing here and what's going to go on in the future is going to be something that's going to be a betterment to all mankind. I'm convinced of that.

138:41:41 Engle: Roger that.

138:41:46 Stafford: Houston, how does your picture look now, and are you saturated at all? Over.

138:41:50 Engle: Roger. We're starting to get saturated now, Tom.

138:41:55 Stafford: OK. It appears that probably when I go to the wide angle enough to zoom it, it starts to saturate a little bit, so I'll keep it down to lower at this time.

138:42:07 Engle: Roger. It's a whole lot better now.

138:42:27 Stafford: Also you notice - How you can really start to notice near the horizons how rugged it is, and do you see the little peaks sticking up on it?

138:42:34 Engle: Roger. We picked, those out.

138:43:04 Stafford: Say, Houston. The Moon, as we move away and our velocity slows down, the Moon is starting to grow less in diameter relative - as far as our visual view, so what we'll do is terminate the TV now and we'll bring it back on in a little while after we squared away here and show you a little bit better distant view. Over.

138:43:30 Engle: OK. Mighty fine, Tom.

138:43:34 Stafford: OK. And this is Apollo 10 signing off for a while, and we'll be back in about 30 or 40 minutes and see how it looks then. Over.

138:43:55 Engle: OK, 10. This is Houston. We'd like to dump the tape now, and we'd like to keep the High Gain Antenna while we do that.

[MCC-H are anxious to downlink the data recorded onboard during the TEI maneuver, to check the performance of the SPS.]

138:44:07 Young: Yes sir.

138:44:15 Cernan: Will this attitude be ok, Joe?

138:44:18 PAO: At the conclusion of the television transmission, Apollo 10 was about 3,390 nautical miles [6,280 km] from the Moon. The Trans-Earth Injection maneuver, which started the spacecraft back to Earth, as you heard early in the television transmission, was very close to nominal. The maneuver is targeted to bring Apollo 10 back to Earth at a Ground Elapsed Time of 192 hours, 4 minutes, or just 4 minutes - 8 days and 4 minutes after lift-off from Cape Kennedy. At the present time the spacecraft is traveling at a speed of 6,046 feet per second [1,842 m/s], and we show 3,436 nautical miles [6,363 km] from the Moon.

138:44:17 Engle: Roger. That will be fine.

138:45:00 Young: Houston. You want to delay - We're going to get the Realign and going to PTC REFSMMAT? That's what you are saying, isn't it? Is that correct?

138:45:07 Engle: That's correct.

138:45:13 Stafford: Roger, Houston. This is 10. We would like to stay in this attitude for a while, if it's ok. If we don’t violate any thermal constraints. Over.

138:45:20 Engle: OK. Let me check on that, Tom. I think that will be ok.

138:45:27 Stafford: All right.

138:45:45 Engle: 10, this is Houston. Roger, Tom. You can stay in that attitude. There is no restraint on the thermal world.

138:45:54 Stafford: OK. Real fine. Thank you, Joe. Over.

[Stafford wants to continue to transmit TV of the receding Moon, but is conscious that they should be setting up the spacecraft in PTC to control the thermal stresses on the spacecraft. They have been essentially in the same attitude since AOS and the Sun has been illuminating the same side of the spacecraft for all of this period. MCC-H is not concerned for a little while longer, after which PTC will be imitated.]

Air-to ground audio

138:48:35 Engle: OK, 10. This is Houston. You can have the computer back now. And your REFSMMAT is in.

[The PTC REFSMMAT has now been loaded. This will allow the IMU to be aligned in such a way that makes it easier for the crew to begin the PTC manoeuvre with the spacecraft side-on to the Sun.]

138:48:46 Young: We've had the computer for quite a while.

138:48:49 Engle: OK. I'm sorry.

138:48:52 Young: I hope. Because we've been playing with it.

138:48:57 Engle: You're right.

[Comm break.]

138:51:20 Cernan: Hello, Houston. This is 10.

138:51:24 Engle: Go ahead, 10.

138:51:30 Cernan: This is - We're circling 26 to 26½ volts up here pretty regularly right at the moment.

138:51:41 Engle: Roger. We copy.

138:51:43 Cernan: We're going to see if we can bring it up a little bit. We're going to see if we can bring it up a little bit. We've got the DDC power off - DEDA power, rather, and a couple of other things, and we'll watch it, but I just wanted to let you know we're looking at a low 26½.

[Cernan is making MCC-H aware that the crew are monitoring the electrical load and are looking to see what items they can safely power down.]

138:52:02 Engle: Roger. We copy. We'll look at it.

138:52:10 Cernan: And I guess we're up to about 27 now, so we're probably in pretty good shape.

138:52:19 Engle: OK, 10. I'm going to turn you over to the Marines now. I'll see you a little later.

138:52:27 Stafford: Roger, Joe. Thanks a lot for all the help there on CapCom and the whole mission is real great. We'll see you back in Houston probably, next Tuesday. Over.

138:52:36 Engle: Roger that. You're right in the groove.

138:52:42 Cernan: Thank you, Joseph.

[Comm break.]

138:54:24 Cernan: Houston, Charlie Brown. Do you want me to put my High Bit Rate to Low?

138:54:30 Lousma: Stand by one. [Pause.]

138:54:41 Lousma: Affirmative, Apollo 10. Put your High Bit Rate to Low.

138:54:49 Cernan: OK. [Long pause.]

138:55:13 Lousma: Apollo 10, Houston. We're going to keep the configuration we’ve got until we get P52 finished and the dump finished. Over.

138:55:26 Stafford: Rog. [Long pause.]

138:55:40 Young: Houston, on these P52s REFSMMAT Realigns, can you give us attitudes to go to so that we can avoid the gimbal lock alarm?

138:55:53 Lousma: Roger. I think we can do that. Stand by. [Long pause.]

138:56:53 Cernan: Hello, Houston. I've got some onboard readouts for you.

138:56:57 Lousma: Roger. Go ahead, 10.

138:57:03 Cernan: OK. Batt C is 37, Pyro A is 37, Pyro B is 37.

138:57:08 Lousma: Roger. Understand Batt B...

138:57:10 Cernan: ...RCS A is 55, B is 7...

138:57:16 Lousma: Apollo 10...

138:57:17 Cernan: ...RCS A is 55 percent - Okay. I'm ready now. RCS A is 55, B is 71; C, 66; D is 63 per cent. [Pause.] Over.

138:57:48 Lousma: Roger, Apollo 10. We copy, 37, 37, 37, 55, 71, 66, 63, and you can do your P52 in the present attitude and go right from there to PTC. Over.

138:58:04 Cernan: OK. P52 in present attitude and right from there to PTC. As it says on page 94 of our Flight Plan, we can tell we're returning because we're facing the other way. A phrase by that one famous dog. [Long pause.]

138:58:47 Cernan: Houston, our condenser exhaust temperature is cycling again between the limits, and I think it just triggered a quick Master Alarm on fuel cell 2, but it's cycling again just like it was in lunar orbit.

138:59:01 Lousma: Roger, 10. We copy. [Long pause.]

138:59:35 PAO: This is Apollo - This is Apollo Control. We're estimating about 15 minutes for the change of shift press briefing as the Maroon team of Flight Controllers goes off shift. Participants will be - stand by.

138:59:49 Young: Houston, Apollo 10. You said it's okay to realign the PTC right now?

138:59:56 Lousma: Stand by one. [Long pause.]

139:00:09 Lousma: Apollo 10, Houston. Go ahead with your PTC alignment.

139:00:16 Young: Roger. [Long pause.]

139:00:28 PAO: This is Apollo Control. To pick up again on the press conference; participants will be Maroon team Flight Director Milton Windler, Spacecraft Communicator Joe Engle, Astronaut geologist Jack Schmitt. They are estimating about 15 minutes arrival at the main auditorium here at the Manned Spacecraft Center. We rejoin the air to ground communications between Apollo 10 and Mission Control.

139:01:10 Lousma: Apollo 10, Houston. We'd like you to turn on your fuel cell 2 H2 purge line heater. Over.

139:01:21 Cernan: Yeah. I've had the H2 purge line heater on about 5 minutes now, Jack.

139:01:26 Lousma: Roger, Gene.

139:01:31 Cernan: And I'm planning a H2 - and an O2 purge at 140. Is that correct, 139:30?

139:01:41 Lousma: Stand by. [Pause.]

139:01:50 Lousma: That is affirmative, Gene. 139:30, purge fuel cells.

139:01:59 Cernan: OK. Thank you, Jack. I assume not fuel cell 1, though. Is that correct? Just 2 and 3? [Long pause.]

139:02:14 Lousma: Gene, just purge 2 and 3, not 1. Over.

139:02:20 Cernan: Thank you, Jack.

[Comm break.]

Air-to-ground audio

139:03:29 Young: Houston, Apollo 10. Confirm that this is an option 1 platform Realign.

139:03:36 Lousma: Houston, Apollo 10. Say again.

139:03:45 Young: Roger. Confirm that this is an option 1 platform Realign.

139:03:48 Lousma: Stand by one.

139:03:51 Young: I’m sure it is. I just wanted you to make sure.

139:03:57 Lousma: OK, John. That's an option 1 confirmed.

139:04:04 Young: Roger.

[When using option 1 in P52-IMU realign, the operator will ensure the preferred orientation is defined, rather than a pre-defined one.]

[Comm break.]

139:06:11 Cernan: Hello, Jack. I've got some Rad readings.

139:06:14 Lousma: Go ahead with the Rad.

139:06:19 Cernan: Commander is 26042, Chimp [CMP] is 05311, and I'm 15043.

[The 'chimp' abbreviation is presumably a nod to the chimpanzees who flew into space aboard the Mercury spacecraft prior to astronauts.]

139:06:29 Lousma: Roger. Copy 26042, 05311, 15043. Thank you.

139:06:37 Cernan: And negative on the - on the pills today.

139:06:40 Lousma: Roger. Copy.

139:06:46 Cernan: And the fans have been cycled.

139:06:50 Lousma: Roger. [Long pause.]

139:07:49 Lousma: Apollo 10, Houston...

139:07:50 Cernan: Houston, we're going through a regulator check at this time.

139:07:53 Lousma: Roger. We copy.

139:07:55 Cernan: Go ahead.

139:07:56 Lousma: Yes. We'd like to know - Did you turn the GDC off by going to ECA? Over.

139:08:04 Stafford: Roger. We turned it off and then turned it back on here since we're going to do this IMU Realign. Over.

139:08:12 Lousma: Roger. Understand off and then on. Thank you.

139:08:17 Stafford: Yep. We want to check again how much it increased our voltage and after we get the IMU completely torqued around, then I'm going to turn the GDC/ECA bar to ECA. Over.

139:08:31 Lousma: OK, Tom.

[Stafford is referring to the SCS-Electronics Power rotary switch on panel 7. Moving it from the GDC/ECA position to ECA removes AC power from the GDC, hence powering it down.]

[Comm break.]

139:10:17 Cernan: Houston, this is 10. When I start up the secondary glycol pump I get a Main Bus A undervolt. Probably is a transient, but I turned it off at this time.

139:10:30 Lousma: Roger. We copy.

139:10:35 Cernan: I'm sure it's a start-up transient, but I haven't start - I haven't tried it again, so recommend we just delete it. It did start up and [garble] the secondary evaporator has been working well. Do you - shall we delete that test or shall we give it a try?

139:10:49 Lousma: Stand by one. We'll check. [Pause.]

139:10:58 Lousma: Apollo 10, Houston. Delete the secondary loop check. Over.

139:11:03 Cernan: Very good. Thank you, Jack.

139:13:17 PAO: This is Apollo Control. Something in the nature of a 'gee-wizz' number: At the time of the Trans-Earth Injection burn, Apollo 10 was some 211,373 miles [391,463 km] away from Earth on the back side of the Moon. Change of shift briefing is scheduled to begin momentarily in the main auditorium. Air to ground Apollo 10 transmissions will be picked up at the conclusion of the press conference; and at 139 hours, 13 minutes Ground Elapsed Time; this is Apollo Control.

[Long comm break.]

[Audio for the period from 139:18:36 until 139:30:16 which should have been recorded during the change of shift briefing, is missing from the released PAO audio tapes.]

139:18:36 Lousma: Apollo 10, Houston, on your next fuel cell purge, fuel cell 3 should be normal 80-second purge. But we'd like you to try something different on fuel cell 2 hydrogen purge. We'd like you to try five cycles on the purge at 15 seconds each, and then 2 to 3 seconds between cycles. So purge for 15, Off for 2 to 3 seconds, and then back on five times. Over.

139:19:10 Cernan: OK, Jack. I'll start right now with hydrogen 2 H2 purge. OK?

139:19:19 Lousma: Roger. We'll be watching.

139:25:40 Lousma: Apollo 10, Houston. If you want to Auto maneuver to PTC, we can give you some angles.

139:25:51 Stafford: [Garble].

139:26:14 Lousma: Apollo 10, Houston. We're not copying you.

139:26:21 Stafford: Roger, Houston. Go ahead with the angles. Over.

139:26:25 Lousma: OK. Roll 105, pitch 90, yaw 0.

139:26:35 Stafford: Roger. Roll 105, pitch 90, yaw 0.

139:26:41 Lousma: That's affirmative.

139:26:47 Stafford: Roger.

139:26:58 Stafford: OK, Houston. And before - What time do you want us to maneuver there? Over.

139:27:07 Lousma: You can maneuver any time, Tom.

139:27:12 Stafford: OK. Before we go there, we're going to give you one last picture of the Moon now – see the terminator coming here - We'll just give you a short look at it if they're still configured for TV. Over.

139:27:25 Lousma: Stand by one.

139:27:36 Lousma: OK, Tom. We're configured. Send it down.

139:29:15 Cernan: Houston, you should have the tube coming down now.

139:29:54 Stafford: Houston, do you have a picture now? Over.

139:30:05 Lousma: We're checking the network time on it.

139:30:07 Cernan: Hello, Houston. Do you have a picture?

139:30:10 Lousma: We don't have it in the MOCR yet, but we are checking the network. Stand by.

Air-to ground audio

Still image from Post TEI TV coverage

TV coverage from 139:30:16.

(Watch video file by clicking above image, or right-click to download.)

139:30:16 Lousma: OK. We got it now. Looks good.

139:30:28 Stafford: When you see the terminator coming on there, it looks like the Moon is lopsided. John is holding the camera, panning, and Gene is opening focus on it. And it's a beautiful view there. Over.

139:30:40 Lousma: Yes. Really looks good from here, Tom.

139:30:45 Stafford: OK. How's your color look on it now? Over.

139:30:50 Lousma: In the MOCR here, we're seeing a green and white Moon.

139:30:55 Stafford: Well. Green and white?

139:30:57 Lousma: Yeah. It's green up near the terminator and white up near the - near the other limb.

139:31:08 Stafford: You must be talking about the cheesy part of it, huh?

139:31:12 Lousma: Yeah. I guess you guys must have done that to it.

139:31:18 Stafford: Yes. You might say something like that. OK. Again, just for correlation on the colors that we have - about the best area of that mare that I can describe, looks like a chocolate milkshake. That's about the best of color of brown that I can describe. Over.

139:31:37 Lousma: Roger, Tom. We copy. Move that camera a little bit to the right.

139:31:47 Cernan: We'll get it in with our monitor. Stand by one. [Long pause.]

[The camera is zoomed in and it takes a while to stabilise. As it does so, it can be seen that an engineer is adjusting the colour. Tom takes much interest in how well the colour TV system is reproducing the colours he sees.]

[The low resolution analogue TV system carried aboard Apollo 10 will have been carefully calibrated to reproduce colours as accurately as the technology will allow. However, it has an innate lack sensitivity to the very subtle hue variations to be seen across the Moon. Even good quality colour film struggles with the nearly monochrome lunar surface. This early colour TV technology finds it very difficult to reproduce the blue/brown differences between Mare Tranquillitatis and Mare Serenitatis. Given the enormous number of processes the signal would pass through to reach the viewer, it would takes only a slight misalignment somewhere for there to be gross colour errors. Colour television is only really worthwhile when there is a highly coloured subject in front of the camera. It works well in the interior of the spacecraft with the flesh tones of the crew and their badges and displays, or on the Moon when we see the gold-coloured thermal film that surrounds the spacecraft.]

139:32:38 Lousma: OK, 10. That's real good.

139:32:39 Cernan: How's it look from here, Jack?

139:32:43 Lousma: That's real good now, Gene.

139:32:49 Stafford: And, Houston, 10. How does your color look? Over.

139:32:56 Lousma: Stand by one, Tom. I don't know if we're getting true color in here.

139:33:02 Stafford: OK. [Pause.]

139:33:09 Lousma: Our color is looking real good now, Tom.

139:33:14 Stafford: OK. [Long pause.]

139:33:43 Cernan: You're looking at the window. The mode now - We backed off so you can see the shade or the shadow of the hatch window, so you got an idea what size it might be if you could see any of the window frame at all. John's backed off to the point where the Moon is out through the hatch window.

139:34:05 Lousma: Roger. I can just make out the edge of the hatch window.

139:34:13 Cernan: It gives you an idea of relative size as to what we're seeing compared to the window itself. [Long pause.]

139:34:56 Stafford: OK, Houston. We just wanted to give you one last show to show how it started - the lighted parts started to look oblong as we can move out and see the terminator start to – continue to move out further and slow down. And it's been real great to - being able to show you this so you can share the same view that we have. Over.

139:35:17 Lousma: Roger, Tom. And it looks real good and I know the folks here at home are really enjoying the show. I bet you feel like you're really moving out.

139:35:29 Stafford: That initial climb out was just fantastic, Jack. Like we were telling Joe earlier that it's a good thing we approached the Moon from the other way because if we approached it from this way straight going like that, you wouldn't - you'd have to shut your eyes. Over. [Long pause.]

139:35:59 Lousma: And, Tom...

139:36:00 Stafford: It's going to be real interesting for us to look at is - Oh. Pardon me. I was just going to say it's going to be real interesting for us to look at the TV films after we get back. Over.

139:36:15 Lousma: Yeah, Tom. I know you'll enjoy that. The TV experts wanted me to tell you that your adjustment of the color camera for both exterior and interior is just perfect. Over.

139:36:31 Stafford: OK. Real fine. Thank you. [Long pause.]

139:36:44 Stafford: OK, Houston. This is Apollo 10. We've been up about 21 hours, nearly 22 hours, and we think we'll go ahead and start setup for the sleep cycle and just go ahead and start with the PTC attitude. And at this time, we'll go ahead and turn the TV off, and this is Apollo 10 signing off for the TV.

139:37:06 Lousma: Roger, Tom. Thanks a lot for the TV show. It's a little early around here for some of the folks, but I know some of them will get it later in the day. It's a real good show.

Air-to-ground audio

139:37:21 Stafford: OK.

139:41:35 Young: Houston, on this PTC, do you want to establish 20-degree deadband at one-tenth of a degree per second, or you want to try this other thing?

[Young commented on the setting up of this PTC session in the post mission crew debrief:

Young, from the 1969 Post Mission Debrief:- "We set up Passive Thermal Control, but this time we were rolling to the left instead of to the right on the first pass. For some reason, it's not known right now, maybe some wrong entries were made in the DAP, but we started with a bad angle. Some thruster firings and roll occurred and it coupled in yaw. We immediately went up against that 30-degree deadband after less than an hour and a half, so we stopped the whole thing and reinitialized it."]

139:41:50 Lousma: John, this is Houston. We want the 30-degree deadband with a three-tenths degree per second. Over. Correction, three-tenths degree per second.

139:42:02 Young: OK. It's set up just the way you did - set up just the way we did coming here. Right?

[Young wants confirmation that they will be using the PTC setup they developed during the TLC.]

139:42:08 Lousma: That's affirmative, John. And when you get down to disabling jets, we want you to disable all jets in quads C and D and we're standing here looking at the procedure, if you want us to help you out on it.

139:42:23 Young: Roger. Understand. Charlie and Dog?

139:42:26 Lousma: That's affirmative.

139:42:30 Young: OK. [Pause.]

139:43:48 Stafford: Hello, Houston. Apollo 10. Over.

139:43:50 Lousma: Go ahead, 10.

139:43:55 Stafford: OK, Jack. Looking ahead in the Flight Plan, what we'd like to do is make this a pretty long sleep period. I understand that the first midcourse occurs in 15 hours and was initially looked at about 1 foot per second, which shows we're right in the slot. And what we'd like to do is sleep in a little bit longer than what was outlined here, see, since we've been up for about 22 hours. Over.

139:44:19 Lousma: OK. Let's get these people to arrange that. Stand by. please.

139:44:26 Stafford: OK. [Long pause.]

139:44:45 Lousma: Tom, looks like we're planned to let you sleep in already and the only thing that would possibly change that Flight-Pan-wise is some P23 activity, which we can postpone. Over.

[P23 is the cislunar navigation program.]

139:45:01 Stafford: OK. We're all of us kind of bushed out now, just a little bit tired from doing all this today, and John particularly. He's really worked hard on that landmark tracking and his eyeballs are a little sore, so if we can postpone that for a little while and just sleep in, we'd sure appreciate it. Over.

139:45:15 Lousma: Sure. We'll work that out. And we want to ask you if you've been getting any caution and warning on fuel cell 2 recently.

139:45:29 Cernan: No. The cycling is still there, but it hasn't cycled into the caution and warning region.

139:45:33 Lousma: Roger. It turns out that the purge fuel cell 2 didn't change anything, and we're trying to work something out, so this won't be bothering you during the time you're trying to sleep. Over.

139:45:47 Cernan: OK, Apparently the package or the pump, or whatever is cycling, doesn’t bother you down there. Huh?

139:45:55 Lousma: Well, the exhaust temperature's getting down near the caution and warning limits. It hasn't gone over them yet. But we thought, if they started doing it, why, it was going to bother you and we're trying to figure out something else.

139:46:11 Cernan: Yeah. I know. But my question is, your analysis of what's causing the cycle, maybe the pump is going on and off, or there's a temperature sensor that's out of balance or something. Whatever you think it might be, it isn't bothering you, huh? [Long pause.]

139:46:40 Lousma: Gene, we're just taking a look at fuel cell 2, and we're analyzing what it's doing, but at the moment, it is of no excessive concern. Over.

139:46:58 Cernan: OK. Thank you.

139:49:02 Lousma: Apollo 10, Houston. We have a presleep checklist here for you. A few items to turn off when you're ready to copy. Over.

139:49:22 Cernan: OK, Jack. Go ahead.

139:49:26 Lousma: OK. Your optics power switch, Off; your SCS Electronics to ECA; and, using Omni for PTC, go to Omni in Bravo. Your High Gain Antenna track, Manual; potable water heater, Off; High Gain Antenna power, Off; your rotational controller power direct, both Off; and, on your Cryo tanks, we want all Cryo fans Off; and on the heaters, reading on your switches from left to right, your H2 tank 1 heater, Off; your H2 tank 2 heater, Auto; your O2 tank 1 heater, Auto; and your H2 tank - correction, your O2 tank 2 heater, Off. Over.

139:49:38 Cernan: OK. On the heaters I got 1 H2 is Off, 2 H2 is Auto, 1 O2 is Auto, 2 O2 is Off, and all my fans are Off.

139:49:51 Lousma: That's right. You got it right.

139:49:56 Cernan: And, let's see. You gave me the ROT power, potable water, heater, High Gain to Manual, power off with the Omni, SCS Electronics, ECA, and optics power Off.

139:51:11 Lousma: Rog. You got them all.

139:51:22 Cernan: Going Omni antenna at this time.

139:51:24 Lousma: Roger.

[Long comm break.]

139:53:XX PAO: This is Apollo Control; 139 hours, 53 minutes Ground Elapsed Time. Apollo 10 is now 7,160 nautical miles [13,260 km] outbound from the Moon, travelling at a velocity of 5,524 feet per second [1,684 m/s].

139:54:43 Lousma: Apollo 10, Houston. We'd like to have you confirm that you're now in the 20-minute wait period with jets on quads Charlie and Dog disabled. Over. [Long pause.]

139:55:23 Young: Houston, we're getting there. We'll do it yet.

139:55:30 Lousma: OK, 10. Just trying to help you out a little bit. Know you guys are tired.

139:55:40 Young: Yes, I know it. We're getting there. [Long pause.]

139:56:38 Young: OK, Houston. We're starting a 20-minute wait.

139:56:42 Lousma: OK, John.

[Comm break.]

139:58:07 Lousma: Apollo 10, Houston. We see your state vector's so good, it doesn't need any updating, so we'll delete that. Like you to ensure that your H2 purge line heaters are Off, and we noted that your DAP is in Auto, and it should he in Free for the 20-minute wait period. Over. Correction - It's in Free, and it should be in Auto for the 20-minute wait period. Over.

139:58:49 Cernan: We got that, Jack - And the heaters were off. Thank you, and we're...

139:59:19 Lousma: Apollo 10, Houston. We're going to hand over to Madrid here momentarily, and you might get a little noise on account of that.

139:59:28 Young: OK, Houston. Would you believe that now we're starting the 20-minute wait period.

139:59:37 Lousma: Roger. I know. We're getting there.

139:59:48 Young: Only problem is that I may fall asleep before the sleep period.

Moon view at 140:00 GET

The view of the Moon at 140:00 GET.

The outline of the rendezvous window gives scale.

[No DSEA recording during this period.]

141:01:XX PAO: This is Apollo Control; 141 hours, 1 minute Ground Elapsed Time. The crew of Apollo 10 is apparently settled in for a long, well-deserved rest period after being up for approximately 22 hours. Had a very successful Trans-Earth Injection burn, powered down the spacecraft and are now in the Passive Thermal Control mode, so called barbeque mode, stabilizing the spacecraft temperatures. They are now some 10,729 nautical miles [19,870 km] outbound from the Moon, coming back toward this speck of cosmic dust we call the Earth at some 5,328 feet per second [1,624 m/s]. And the situation is rather quiet here at the Control Room, looking at playback data from the Trans-Earth Injection burn. And 141 hours, 2 minutes Ground Elapsed Time; this is Apollo Control.

142:01:XX PAO: This is Apollo Control; 142 hours, 1 minute Ground Elapsed Time. Apollo 10 crew is apparently asleep at this time. We've had no communications from them within the last hour or so. Some numbers on distance: reference distance is now 198,243 nautical miles [367,146 km]; velocity, 4,780 feet per second [1,457 m/s]. Flight Surgeon just reported to the Flight Director that commander Tom Stafford is apparently in a rather deep sleep according to the biomedical readout. Some other numbers now on the current predicted Entry Interface; 191 hours, 48 minutes Ground Elapsed Time with splashdown about 14 minutes later at 192 hours, 2 minutes; just 2 minutes over 8 days even. This would be 11:51 Central Daylight Time. These numbers likely will change as additional tracking is brought in and processed through the computers here in Mission Control Center. Major events today will be include another television transmission at 152 hours, 35 minutes Ground Elapsed Time. The accuracy of the Trans-Earth Injection burn was such that the first midcourse correction, midcourse correction burn number 5 at TEI + 15 hours is estimated to be only 2.6 feet per second [0.8 m/s]. Here again, this may be allowed to accumulate to add to a later midcourse correction scheduled time. At 142 hours, 3 minutes Ground Elapsed Time; this is Apollo Control.

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