Leaking tunnel and Jettison of the LM	Journal Home Page	Day 10: Orbital Science

Apollo 15

Orbital Science and Crew Rest

Corrected Transcript and Commentary Copyright © 1999 by W. David Woods and Frank O'Brien. All rights reserved.

[This is August 3, 1971, the ninth day of the Apollo 15 mission.]

Public Affairs Officer - "This is Apollo Control at 191 hours, 44 minutes. Apollo 15 - Endeavour is nearing the end of the front side pass of the 58th lunar revolution. The crew is still asleep, 1 hour, 45 minutes left in this rest period. We have changed shifts here in the control center. Flight Director Gerry Griffin has relieved Flight Director Gene Kranz. CapCom now is astronaut Joe Allen. ... At 191 hours, 45 minutes; this is Mission Control, Houston."

[The late jettison of the Lunar Module yesterday evening has delayed the crew's planned 9-hour rest period. Mission Control have cut them some slack because, at Al Worden's first call of the day, it is 9½ hours since he last spoke to them. Because of this late start, there are over three pages of Flight Plan activities which must be rescheduled or deleted.]

[Flight Plan pages 3-296, 3-297, 3-298, 3-299, 3-300, 3-301, 3-302, 3-303 and the current page, 3-304.]

192:45:16 Allen: Good morning, Alfredo. This is Houston.

192:45:22 Worden: Good morning, Dr. Joe. How are you?

192:45:29 Allen: Couldn't be better, Al. How's it going?

192:45:32 Worden: Just fine, Joe. You all talked out?

192:45:34 Allen: No, sir. Just getting ready to start. And, pleased to have a chance to talk to you.

[Joe Allen was the EVA CapCom for Dave and Jim while they were on the surface and has had little chance to talk to Al over the past four days.]

192:45:41 Allen: I've got all kinds of things for you, Al, when you...

192:45:43 Worden: Very good, Joe. Glad to be talking to you.

192:45:45 Allen: Okay. I've got all kinds of things for you, which I can start handing it up to you at your convenience, pretty much. We're going to change the Flight Plan around a little bit - primarily, lifting out things because of our getting a somewhat later start than normal, and a couple of other minor modifications. I also have a lot of news to read to you and some other good things you might be interested in. Over.

192:46:15 Worden: Okay, Joe. Let's - why don't you give me a couple of minutes here to get some pens and the Flight Plan out and - and in about 5 or 10 minutes or so, I'll have the guys put the headsets on and we'll all listen to the news.

192:46:30 Allen: Al, out of curiosity, is everybody awake up there?

192:46:37 Worden: Yeah, man.

192:46:39 Allen: Good morning, Davy...

192:46:40 Worden: Yes, Joe, sure are. We're just in the middle of breakfast.

192:46:45 Scott: Hello, Joe. How are you?

192:46:46 Allen: Well, I'm fine, D.R.; how are you today?

[Allen is using the initials of Dave Scott's forenames, David Randolph. His middle name comes from the fact that he was born on Randolph Air Force Base on 6 June 1932.]

192:46:51 Scott: Oh, we're in great shape. Hey, you sure did a fine job for us down there, Joe. Jim and I'd like to really thank you. That was a superfine job of taking care of everything for us.

192:47:01 Allen: I think the superfine job is the two of you; it was just most remarkable. Everybody down here is still floating so high, they're having a hard time getting down to all that data you gave us. And you'll be interested to know that - that we have sitting in front of us, a preliminary report from each EVA of the geology of the area that I would say is more complete than our 90-day preliminary reports which were issued on some of our other landings. It's just most exciting.

192:47:38 Scott: Well, it's because you've got the real professional backroom there. Those - those guys really know how to put - put it together. Especially with the way they were coming up with the new ideas, while we were on the surface. That was really neat.

192:47:52 Allen: And, Dave, I do have to ask you one question. Is there a three-unit segment of deep core stems some place in that Command Module?

192:48:02 Scott: Joe, we wouldn't lose sight of that for all the tea in China. That's number 1 priority.

192:48:09 Allen: Yes sir. [Long pause.]

[The deep core sample was one of the major frustrations for Dave on the surface as it proved very difficult to extract, costing both time and a trip to visit the North Complex at the Hadley landing site. In addition to the problems of trying to pull the core stem out, they found that a vice, mounted on the Rover for the specific task of dismantling the six half-metre sections, was fitted backwards and unable to grip the stem. By other means, Dave got three sections free but they collectively decided to bring the remaining 1½-metre length back to Earth intact. In view of how much Dave has invested in this section he would not let it out of his sight.]

192:48:55 Allen: Okay, Dave. Good news; good news. Al, if you're ready, I'll start hitting you with a few things we're interested in knowing from you right away. And then, when we get those, I'll give you the general plan for the day. And I think, in some cases, we'll want to just talk you through some of the changes while you're making your front-side pass. There's no need to feed up all the data in detail to you at the beginning here. My first question: we need from you a configuration of panel 230, particularly - in fact, only really the Mass Spec. switches, could you - call out the settings for the Mass Spec., Experiment switch, Ion Source switch, Multiplier switch and Discriminator switch, please.

[Panel 230 is the control panel for the SIM (Scientific Instrument Module) bay.]

192:50:03 Allen: Okay, thank you. That's - that's what we'd guessed. And, Al, I - I guess the first thing we want - we're going to want you to do today is to start to get ready to go plus-X forward, P20 option 5. We're going to want you to retract the Mass Spec. boom and close the X-ray and Alpha Particle cover.

[Allen is covering some of the tasks which were in the timeline through which they have slept.]

[Overnight, Endeavour has been orbiting the Moon with its main engine facing the direction of flight, the so-called Minus-X Forward SIM Attitude. This attitude not only points the SIM bay at the surface below, it also aims the inlet of the Mass Spectrometer in the direction of flight so as to ram any molecules of the tenuous lunar atmosphere into the sensor. They are finished with this period of operation and want to change to a pointy-end-forward attitude with the SIM bay still looking down. This turnaround maneuver is always preceded by a manual roll of the spacecraft 40° clockwise. If they do not do this, there is a strong possibility that the turnaround will cause the IMU to enter gimbal lock, a condition that would cause it to lose its alignment.]

[Terminating this use of the Mass Spectrometer includes the retraction of its boom, an operation which has been giving some problems on previous attempts.]

192:50:44 Allen: Okay, real fine. You can start that right now at - just put it in at 192:52, I guess. And also, right after that, list fuel cell purge, H₂O dump and LiOH canister change.

[Allen is essentially trying to hustle Al through the most important housekeeping tasks that need to be done to cover the missed period between the planned and actual wakeup times.]

[Worden, from the 1971 Technical Debrief - "You never know what the configuration of the SIM bay is. I think that's particularly true with the three of us in the CM and all of us operating the SIM bay. We never knew if the booms were in or out, whether the experiments were on or off, and just what was going on in the SIM bay. I think that added to some of the confusion."]

[Scott, from the 1971 Technical Debrief - "That's right. And in retrospect, it seems to me the best plan, with three people in the CM running the SIM bay, is to assign one man to do nothing but SIM bay operations. Let him concentrate 100 percent on SIM bay, and the other two people can do the stowage, cleanup, and fix the meals. With three trying to run the SIM bay, I'm sure we all weren't very well coordinated."]

192:51:46 Allen: Al, let me hit you with that last statement again. We want you to retract the Mass Spectrometer boom, but not the Gamma-ray, and close the X-ray and Alpha Particle covers. Retract Mass Spec. boom and close two covers. Over.

192:52:09 Worden: Okay, understand. You want us to pull in - to retract the Mass Spec. boom and close the X-ray [and] Alpha covers, then do the fuel cell purge, the water dump and canister change.

192:52:22 Allen: That's affirm.

192:52:28 Worden: Okay, Joe. I'll get that in work.

192:52:36 Allen: And one more item. You can start to charge Bat B at your convenience.

[The CSM's online batteries are regularly recharged during the flight as they help cover extra power demands from the spacecraft's systems. At the end of the mission, they will be used to power the separated Command Module during the re-entry into Earth's atmosphere. This charge was due at 189:00. The replacement of the lithium hydroxide canister was due at 192:00 and requires that canister 16 replace number 13 in the A receptacle, 13 being stowed in compartment A3. The purge and dump were due in an hour.]

192:52:56 Allen: Okay, and looking downstream here, as soon as you get turned around, and these other good things done, we're going to ask you to open the X-ray and Alpha Particle covers. And for rev 60, the [current] agenda calls for an eat period for you. And Gamma-ray, X-ray and Alpha Particle data being taken during that time. Sounds like you've got your eat period pretty well out of the way.

192:53:27 Worden: Yes, that's right, Joe.

[Long comm break.]

[There is an eat period scheduled during rev 60 which lasts from 194:30 to 195:30. Allen seems to be confirming that they have just eaten their breakfast, presumably so that the later meal break can be used for rescheduling missed tasks.]

192:56:37 Allen: Go ahead, Al.

192:56:40 Worden: Okay, Joe. While we're maneuvered here to a plus-X forward, how about reading some news to us?

192:56:45 Allen: Okay. Sure will. Let me - let me begin with just a note on that water dump. It'll take about 15 minutes to run, and they're interested in your dumping it to close to 10 percent onboard reading. Over.

192:57:04 Worden: Roger, understand. Probably the same as we've been doing before. We dump down to 10 percent, but not below 10 percent.

192:57:12 Allen: That's correct. And I've got several things to read to you here. I have the official morning Gold Bugle Zeitung report and - that comes from two rows behind me here. And I've also got a telegram for you, Jim. And I have some history - a little bit of history that's been researched for you by the people at Honeysuckle concerning a small problem with a leak on the Endeavour about 200 years ago. And I'll start with whatever you'd like to hear first.

192:58:07 Worden: Okay, Joe. Go ahead.

192:58:09 Allen: Okay, let me just start with the morning's news. The weather report in Houston-Galveston area calls for showers and thunder showers through Wednesday. Today's temperatures will be in the lower 70s and upper 80s.

192:58:09 Allen: The United States will support Communist China's admission to the United Nations this fall, Secretary of State, William Rogers announced. The U.S. will also fight against expelling the Nationalist Chinese Government on Taiwan. U.S. Steel, the industry pace setter, announced a price hike averaging 8 percent on virtually all its products and several other companies followed suit, as an aftermath of a new 3-year labor contract. Trainmen won pay increases of nearly a dollar and a half an hour, spread over a 42 months, in a nationwide contract settlement, and called off their crippling strike against ten railroads. The union yielded on the railroad's demands for some work-rule changes, yet to be worked out. Among those viewing Apollo 15 activities, Monday, in the MOCR, was artist Robert McCall, designer of the commemorative stamp for Apollo 15. And just an edited note here: He was also making sketches of the scenes down here as he saw them and he would turn them out almost as fast as the photographer would take pictures. That was most interesting. Turning to the sporting news, Don Wilson pitched a two-hitter and Jesus Alou drove home the winning run and then made a game-saving catch as the Houston Astros downed the Chicago Cubs, 2 to 1. And, apparently, rain is slowing up the Oilers' preparations for the Giants. The Oilers/Giant exhibition game is scheduled for Monday night in the Astrodome. And I've got the Monday's baseball scoreboard - which I'll run through quickly for you baseball fans. In the American League: Boston 7, Baltimore 4; New York 7, Cleveland 0; Oakland 2, Kansas City 1; Chicago 7, Minnesota 5; Detroit 11, Washington 7; California 3, Milwaukee 1. Readback.

[Joe's excellent and quick sense of humour turns a list of baseball scores into another reading of Pre-Advisory Data (PAD) which are always read back to Mission Control for verification.]

192:59:38 Worden: Roger, Joe. Copied all these off.

192:59:38 Allen: Roger. Okay. In the National League: Philadelphia 4, Atlanta 0; Cincinnati 4, New York 2; St. Louis 3, San Diego 1; and Los Angeles 5, San Francisco 4. And Lee Trevino added another thousand bills to his bank roll, Monday, by taking first place with the number ... with a 7-under-par, 65, in the Colombus Invitational Pro-Am. Jack Nicklaus and Arnie Palmer teamed last weekend to close in on Trevino in professional golf's money-winning race, though. Nicklaus and Palmer won twenty thousand dollars each when they won the National Team Championship at - I guess Ligonier, Pennsylvania. Trevino leads for the year with a total of nearly two hundred thousand dollars.

[Flight Plan page 3-305.]

[Woods, from 1999 correspondence - "Did NASA heap a lot of PR work on you when you returned or did they give you decent grace to debrief, unwind and get your bearings again after the flight?"]

[Scott, from 1999 correspondence - "The former - and I wish we had had the latter. But NASA was a very large organization, and we were essentially 'transferred' to the PR world after the flight; and during those days there was very little sensitivity to the issues you suggest. Actually, it would have been best if we had had a quarantine period of three weeks or so as did previous flights, just to rest up and get ready for the next push (which I requested of Slayton but to no avail). But no complaints really, we did get to go on some fabulous and memorable trips which we would trade for nothing."]

193:05:43 Scott: That's quite an analogy, isn't it.

193:05:48 Allen: Quite an analogy, Dave. Certainly is.

[Journal reader, Andrew Field, points out that Captain Cook's Journal is available online from the National Library of Australia. from this resource, we can get exact quotes for the passages given above. For the entry where the ship is grounded, it says "Before 10 oClock we had 20 and 21 fathom and continued in that depth untill a few Minutes before a 11 when we had 17 and before the Man at the lead could heave another cast the Ship Struck and Stuck fast. Emmidiatly upon this we took in all our sails hoisted out the boats and sounded round the Ship, and found that we had got upon the SE edge of a reef of Coral rocks having in some places round the Ship 3 and 4 fathom water and in other places not quite as many feet, and about a Ships length from us on our starboard side / the ship laying with her head to the NE / were 8, 10 and 12 fathom." When the crew try to lighten the load, it says "We not only started water but throw'd over board our guns Iron and stone ballast Casks, Hoops staves oyle Jars, decay'd stores &ca, many of these last articles lay in the way at coming at heavyer. All this time the Ship made little or no water."]

193:06:17 Worden: Okay, stand by, Joe. [garble]

[Comm break.]

193:07:40 Allen: Okay, Alfredo. GET 191 plus 25; RCS total, 47 [percent]; quad A: 50, [B] 47, [C] 46, [D] 47; H₂ tank 1: 56, [2] 53, [3] 42; O₂ tank 1: 64, [2] 67, [3] 54.

193:08:19 Worden: Roger, understand, Joe. At 191:25, RCS total, 47; quad A: 50, 47, 46, 47; H₂ is 56, 53, 42; O₂ is 64, 67, 54.

[Though the major events of the flight have passed, they have barely used half of their critical consumables. This reflects the margins built into the system to cope with credible emergency situations. For example, if there had been an Apollo 13-type abort or the CSM had been called on to rescue the LM from an off-nominal orbit.]

193:08:54 Worden: Okay, Joe. [Long pause.]

193:09:37 Allen: Endeavour, this is Houston again.

193:09:42 Worden: Go ahead, Houston.

193:09:44 Allen: Okay, Al. Let me lay some more words on you concerning your Flight Plan, when you're - you're ready to talk about that.

193:09:55 Worden: Roger, Joe. Go ahead.

193:09:58 Allen: Okay. You'll be in the configuration plus-X forward, and will be taking Gamma-ray, X-ray and Alpha Particle data, data during rev 60. We want you to do, at 193 plus 45, a P52 option 3. And we're going to add a Map and Pan Camera pass sometime during rev 60. And I'll be coming at you with the necessary data for that. Also...

[Allen is replacing the P52 guidance platform realignment scheduled for 190:15. This will realign the platform to the orientation of the landing site at the time of lift-off, known as the lift-off REFSMMAT. During the three hours this morning when the crew caught up on their rest, periods of photography by the Mapping and Panoramic Camera were also scheduled which must now be given time later.]

193:10:53 Allen: Okay, Al. Now I guess a - a word about biomed configuration, today. In order to get some very interesting baseline data, medical data on you, Al - and, Jim, for your EVA coming up later - we're requesting that the two of you give us that biomed data today. I think, Dave, you were scheduled for it, but I guess we'd prefer Jim on the line with Al to get baseline data for later. Now, Al, let - let me run through in just some blocks here, [of] the next revs as we see them, and the approximate activities. And then I'll come up with specific data concerning those revs later on, perhaps actually during the revs. On rev 61, we're going to have the UV...

[The requirement for Jim to wear his biomedical sensors may be linked to heart irregularities spotted by the Flight Surgeon while on the Moon.]

193:12:54 Allen: Okay. On rev 61 will be UV photography of the lunar mare. We're coming up on, I guess, an hour of light flash experiments, and it's pretty much dealer's choice between Dave and Jim, who - whichever one of you would like to do that. Rev 62 will be a crew exercise period, science photos, and science visuals. And we'll be taking the Mapping Camera and Laser Altimeter data during rev 62. And it will end with terminator photos. On rev 63, more Mapping Camera, Laser Altimeter, and a burst of the Pan Camera. UV photos and terminator photos again. Rev 64 will be eat period, boom photos, LiOH canister change; and that brings us to about 204 hours, and it'll be time to go to bed again. Over.

[This outline roughly follows the Flight Plan anyway.]

193:13:18 Allen: That's exactly right, Al. And you'll be coming on to it kind of as the day progresses. We're just going to pick up a few quick items that we've missed over the past 2 hours and mainly just lift - lift out other sections, as I understand it. But you'll be back on the Flight Plan shortly.

193:13:40 Worden: Okay, Joe. Fine. Thank you.

193:13:41 Allen: Roger. And...

193:13:42 Scott: And, Joe, let me request that Jim be...

193:13:48 Allen: Go ahead, Dave.

193:13:51 Scott: I'd like to say that I'd like to have Jim without his sensors on today. That 3 - 4 days in a row is pretty tough with those things on. I think probably, if we get him tonight, you could probably get your data, don't you think?

193:14:10 Allen: Stand - stand by, Dave, and I'll - let me double check,

193:14:26 Scott: Say, as a matter of fact, Joe, why don't you give Jim and Al both a break today on the sensors, and I'll stick mine on, because I've had them off since we got back yesterday. And then if you want us to have some particular data-gathering periods, why don't we take a look at that starting tonight, huh?

193:14:46 Allen: Okay, Dave. That sounds good.

193:14:51 Scott: Okay. And concerning the light flash things - Jim and I both saw light flashes while we were on the surface, as a matter of fact.

193:15:01 Allen: Okay, copy that, Dave. That's remarkable.

[Long comm break.]

193:20:59 Scott: Go ahead, Houston.

193:21:02 Allen: Roger. On our downlink data, we see indications of High Gain Antenna yaw fluctuations. Wonder if you could glance over at your onboard indication and see if you see it there as well. And, also we're standing by for crew status reports, when you're ready to give it.

193:21:31 Scott: No, we - we see no oscillations up here, Joe.

193:21:34 Allen: Okay, thank you.

[Comm break.]

193:22:58 Worden: Okay. Jim will be ready to copy a TEI PAD here in a minute. And Mass Spec. boom retracted without a hitch this time, Joe. Sorry I didn't get the time on it, but it was very close to the nominal time, and apparently it didn't hang up this time.

193:23:15 Allen: Okay, fine, Al. Thank you. We'd like the - I guess the Mass Spec. placed on Standby, please. And that's the Experiment switch.

193:23:26 Worden: Okay. Mass Spec. on Standby. Yes, that's verified on standby, Joe.

193:23:38 Allen: Thank you. [Pause.]

193:23:47 Irwin: And, Joe, I'm ready to copy that TEI PAD.

193:23:51 Allen: Okay, Jim, good morning. We need Accept, and we're going to uplink a new state vector to you.

[The state vector is a collection of seven values stored within the computer which define the spacecraft's position and velocity along three orthogonal axes at a specified time. The computer uses it to do calculations concerning the spacecraft's motion. After a time, small errors in these calculations build up and at regular intervals, Mission Control compare the spacecraft's state vector with one they calculate themselves based on radar tracking from Earth. If necessary, they can upload a revised state vector to the CSM by having the crew place the Up Telemetry switch from Block to Accept.]

[An interpretation of the PAD follows:

Purpose: This PAD details a burn which would, in an abort situation, be made to return Apollo 15 to Earth. It would occur towards the end of the 62nd orbit.

System: The burn would be with the SPS engine under the control of the Guidance & Navigation System.

CSM Weight (Noun 47): 36,310 pounds (16,470 kg).

Pitch and yaw trim (Noun 48): 0.61° and 0.92°. These are the angles for pointing the SPS engine bell to ensure its thrust acts on the spacecraft's centre of gravity.

Time of ignition, T_ig (Noun 33): 200 hours, 10 minutes, 34.64 seconds.

Change in velocity (Noun 81), fps (m/s): x, +2,928.4 (+892.6); y, +190.3 (+58.0); z, -43.5 (-13.3). Velocity components are expressed with respect to the local vertical/local horizontal frame of reference.

Spacecraft attitude: Roll, 180°; Pitch, 106°; Yaw, 6°. These attitudes are expressed with respect to the lift-off REFSMMAT.

Other items in the standard form are not applicable (NA) to this burn.

SPS propellants are settled in their tanks by firing the plus-X thrusters on all four quads around the Service Module for 12 seconds.]

193:25:28 Allen: Okay, Jim. Readback correct. And how are you doing this morning?

193:25:37 Irwin: Fine, Joe. Had a good night's sleep.

193:25:42 Allen: Super. [Pause.]

193:25:49 Worden: Okay, Joe, I've got a clear status report for you.

193:25:52 Allen: Go ahead.

193:25:58 Worden: Okay. Longest 9 hours sleep in one period there, Joe, to begin with. And the PRD's are 25024, 08031 and 23175.

193:26:19 Allen: Okay, Al, copy that. And assume there was no medication.

193:26:26 Scott: That's affirmative.

193:26:28 Allen: Okay, thank you, Dave. [Long pause.]

193:26:43 Allen: Endeavour, you can go back to Block. You have a new state vector and we're standing by to watch your water dump.

193:27:00 Scott: Okay, Joe, crank out the water dump. Want to watch one for a change, huh?

193:27:06 Allen: Roger, lay it on us.

[Long comm break.]

193:33:06 Irwin: Stand by one, please, Joe.

193:33:07 Allen: Roger.

[Comm break.]

193:35:49 Allen: Okay, Al. And I - I forgot to tell you when you are dumping water, you can also go ahead with the urine dump if you need to do that. I just forgot to mention that. The Map Camera photo PADs for rev...

193:36:03 Worden: That's okay, we're doing it.

193:36:04 Allen: Yes. For rev 60. T-start, 194:35:05, T-stop, 195:34:50. Image motion setting at T-start: barber pole plus 4; At 195 plus 20 plus 00: barber pole. And a couple of notes on this. Be sure to retract the Gamma-ray boom prior to the start of the camera pass. And be sure to go to 5 degrees deadband in P20 - I'm sorry, Al; that's 5/10ths of a degree deadband in P20 prior to camera pass. And you want to extend the camera and start the Laser Altimeter per the system's checklist, page S/1-38. Over.

193:37:41 Worden: Roger, Joe. Understand. Mapping Camera photo PAD: T-start, 194:35:05; T-stop, 195:34:50. Now for the image motion, you want a T-start barber pole plus 4, and at 195:20:00, you want that increased to barber pole. And notes: Retract the Gamma-ray before taking the pictures; go to half degrees deadband; and extend the Mapping Camera; and start the Laser Altimeter as per system's checklist S/1-38.

[Whereas the science instruments in the SIM bay do not require accurate pointing, the Mapping Camera does. The deadband, the allowable error in the spacecraft's attitude before corrective jet firings are made, must therefore be narrowed from 5° to ½°. The tracking program in the computer, P20, takes care of keeping one side of the spacecraft aimed at the Moon and this is where the new value must be entered.]

[Comm break.]

193:41:25 Worden: Okay, Houston. Go ahead.

193:41:27 Allen: Roger, Al. We want O₂ Heater in tank 3 to Auto and tanks 1 and 2, Off. Over.

193:41:40 Worden: Understand, Joe. You want O₂ Heater in tank 3, Auto, and the other two, Off.

[The heaters within the cryogenic storage tanks can be controlled automatically to keep tank pressures within limits. Pressure switches route power to energise motor-driven switches which, in turn, route current to the heaters when required. During periods of low power consumption, heat leakage from the tank's ambient environment can be enough to keep the tank pressurised and its contents flowing properly to the fuel cells and ECS (Environmental Control System). Otherwise, the heaters will come on to restore feed pressure.]

[This request from Allen is instead of a couple of lines in the Flight Plan which call for the exact opposite. (Tanks 1 & 2 to Auto, tank 3 to Off.)]

193:41:59 Worden: Roger, Joe. We'll get that in work here now.

[Comm break.]

193:45:30 Allen: Endeavour, Houston. Requesting Auto in the High Gain [Antenna]. And, troops, you may have to delay the P52 we've called out to you and coming up shortly until about 194 plus 20, to make sure most of the water is out of the way. Over.

193:45:56 Worden: Roger, Joe. I'll just go take a look here and see - If I can pick up the star okay, I'll go ahead and do the P52.

[To accomplish a realignment of the guidance platform, Al has to sight through the spacecraft's optics at two stars. Experience on previous flights has shown that soon after a water or urine dump, it can be difficult to distinguish the stars among the cloud of tiny ice crystals reflecting the sunlight. However, as they have just passed into lunar night a few minutes ago, this will not present a problem and Al can proceed with the task.]

193:46:11 Worden: Right. Roger. We got it turned off.

193:46:14 Allen: Thank you, sir.

[Long comm break.]

193:51:15 Allen: Go ahead.

193:51:19 Worden: Okay, Joe. I got the gyro torquing angles up, and I'll torque them out in a minute.

193:51:26 Allen: Standing by.

[Comm break.]

[Al calls up three angles on the DSKY (Display and Keyboard) to allow Mission Control to make a note of them. They are the angles by which the three gimbals supporting the guidance platform must be rotated to restore perfect alignment.]

193:53:54 Worden: Okay, Joe. We'll be about another 2 or 3 minutes finishing up all the dumps, and then we'll do that.

193:54:00 Allen: Okay. Fine. We do want you to wait until all the dumps are completed, and then open the doors and turn Alpha Particle on at your convenience, really.

193:54:11 Worden: Roger.

[Comm break.]

193:55:26 Worden: Okay, Joe.

[Very long comm break.]

[Flight Plan page 3-306.]

[Endeavour's 60th orbit of the Moon begins at about 194:18 GET.]

[Six minutes before AOS (Acquisition Of Signal), Endeavour passes across the terminator and into lunar day. In preparation for this, Al has extended the Mapping Camera out on its track ready to begin a period of mapping photography which will continue until they reach the opposite terminator.]

[This period of mapping photography was essentially postponed from this morning as the crew were allowed an extended rest. At this time, the deadband is changed from 5° to ½°.]

194:43:09 Allen: Hello, Endeavour. This is Houston. [No answer.]

194:44:24 Allen: Hello, Endeavour. This is Houston.

194:44:32 Worden: Hello, Houston; Endeavour. Loud and clear.

194:44:35 Allen: Roger, Al. I wanted to tell you that, except for a couple of minor changes, you'll shortly be back on the nominal Flight Plan. I do have a Pan Camera photo PAD to be copied into your Flight Plan at 195 plus 00 when you're ready.

194:44:55 Worden: Okay, Joe. Go ahead.

194:44:58 Allen: All righty. At 195 plus 00, Pan Camera Mode, Standby; Power, On; Stereo, Exposure, Normal. At 195:04:13, Pan Camera Mode, Operate. At 195:14:30, Pan Camera Mode, Standby. Pan Camera Mode, Mono, at 195 18 23; Pan Cam Self Test to Self Test. The talkback should be barber pole for 30 seconds and then gray. And after the talkback is gray, Pan Camera Self Test to Heater. At about 195 plus 21, Pan Camera Power, Off, on a cue from MSFN. At - at 195 plus 34 plus 50, Laser Altimeter, Off; Retract Map Camera; and Close Map Camera Cover, per steps 7 and 8, page S/1-39 in your checklist. Over.

194:47:38 Worden: Okay, Houston; understand. And I'll go through the whole thing here for you. At 195, Pan Camera Mode, Standby; Power, On; Stereo and Exposure, Normal. At 195:04:13, Mode to Operate. At 195:14:30, Mode, Standby, and Stereo to Mono. At 195:18:23, Self Test to Self Test, and barber pole for 30 seconds and then Self Test to Heaters. At 195:21:00, Pan Camera Power to Off on your cue. At 195:34:50, Laser Altimeter, Off; Retract the Mapping Camera, and close the covers per steps in checklist S/1-39.

194:48:39 Allen: Okay, Al. Right on. And could you verify for us, please, that the Alpha Particle Spectrometer has been turned on and that the X-ray and Alpha Particle covers are open. Over.

194:48:55 Worden: Okay, Joe. The covers are open. X-ray is On, and Alpha Particle coming On now.

194:49:02 Allen: Okay, thank you. And, Endeavour; we need Narrow Beam on the High Gain [Antenna], please.

194:49:16 Worden: Got it. [Pause.]

194:49:27 Allen: Okay, Al. Thank you.

194:49:33 Worden: Roger, Joe.

[Comm break.]

194:51:24 Allen: Go ahead, Al.

194:51:29 Worden: Joe, looking ahead a little bit in the Flight Plan, I see we've got gegenschein coming up on this rev. And I guess my question is do you want me to change the film in the - in the camera now? In other words, have we missed any picture taking with the - the - the Nikon that maybe we want to pick up with that mag before I offload that mag?

[Al is referring to the second, ultimately unsuccessful attempt to photograph the gegenschein, a patch of light believed to be caused by the scattering of sunlight off particles that have collected at one of the Lagrangian points. To do this, he uses the Nikon 35-mm camera with a f/1.2 55-mm lens and 6,000 ASA film.]

194:52:22 Worden: Okay, now, Joe. You're right. I don't know - I don't know where we got - got our wires crossed, but the covers were closed and they're now open.

194:52:31 Allen: Okay, no problem. Good. [Long pause.]

194:53:33 Allen: Al, on your question on the gegenschein experiment, we want you to go ahead and change the mag to Victor, just per the Flight Plan.

194:53:44 Worden: Okay, Joe. Thank you.

[Long comm break.]

194:57:51 Worden: Hello, Houston. This is Al.

194:57:54 Allen: Roger, babe. Requesting you - give us a Gainstep on the Gamma experiment up three clicks, please. And we're also wondering what mag you've taken off the Nikon to put mag Victor on. There's some confusion in our minds. I guess we thought Victor was already on there. Over.

194:58:18 Worden: Negative. Mag U was on there before, Joe, and I had just taken it off.

194:58:23 Allen: Okay, thank you, Al. That helps us. And once again, the Gainstep on the Gamma, up three clicks. And we're showing that now.

194:58:33 Worden: You've already got it.

194:58:34 Allen: Thank you.

[Long comm break.]

[Flight Plan page 3-307.]

195:02:11 Worden: Auto it is. [Long pause.]

195:02:59 Allen: Endeavour...

195:04:00 Allen: Mark. 15 seconds to Pan Camera, Off - On, Pan Camera, On. Sorry.

195:04:06 Worden: Roger. Roger. Got you, Joe.

195:04:14 Allen: Pan Camera, On.

195:04:20 Worden: It's On.

[Long comm break.]

[Readers should note that NASA habitually use the term "weight" although it was and is generally recognised to be erroneous in this context. The correct term is "mass". Mass refers to the quantity of matter within a particular body, be it atom, spacecraft or galaxy. Place a mass within a gravity field and it will experience a force pulling it towards the source of the field. On Earth, though many of our scales are calibrated in kilograms, the standard unit of mass, in truth they depend on measuring the force acting on the body. This force is what we know as weight and it will vary from place to place. In the free-fall condition that the spacecraft is in, it has no weight. It is weightless. However, it still has mass.]

195:14:11 Worden: Roger, Joe. Thank you. [Long pause.]

195:14:31 Allen: Pan Camera to Standby.

195:14:38 Worden: Pan to Mono.

195:14:42 Allen: We copy, and thank you, Al. And I've got a UV photo PAD, a big one liner, when you're ready to copy that.

195:15:01 Worden: Okay, Joe. Go ahead.

195:15:02 Allen: Roger. This is for your PAD located at 196 plus 50. And it is T-start, 196:56:19.

195:15:21 Worden: Understand, Joe. UV photo PAD. T-start, 196:56:19.

195:15:28 Allen: Right on, Al. Thank you. [Long pause.]

195:16:01 Allen: Endeavour. 30 seconds to Self Test.

195:16:13 Worden: Roger.

195:16:27 Allen: Al, I gave a bad call. I was 30 seconds premature on that. Stand by.

195:16:35 Worden: Okay. Looks like you'll get two Self Tests, Joe.

195:17:06 Allen: Al, that's no problem. We'll take both of them, and I'll cue you for the next.

195:17:14 Worden: Okay. I'll give you a whole series of them if you want them.

195:17:27 Allen: Negative, Al.

195:17:54 Allen: 30 seconds to Self Test.

195:18:00 Worden: Roger. [Long pause.]

195:18:22 Allen: Mark. Self Test.

195:18:29 Worden: Roger.

[Comm break.]

195:20:04 Allen: Thank you, Al. [Long pause.]

195:20:19 Allen: Okay, Al, and on the Map Camera, Image Motion to barber pole, please.

195:20:28 Worden: Roger.

[Long comm break.]

195:29:28 Allen: Hello, Endeavour, this is Houston.

195:29:35 Worden: Houston, Endeavour. Go ahead.

195:29:41 Allen: Roger, Al. I've got what they tell me is the last change to your Flight Plan to put you back on the nominal.

195:29:52 Worden: Okay, Joe; stand by just one.

195:29:54 Allen: Okay. No hurry.

[Comm break.]

[Al should begin getting ready for the gegenschein photography about now. The Nikon camera is installed in window 4, the right rendezvous window, and will therefore be looking along the spacecraft's longitudinal axis.]

195:31:14 Allen: Okay, Al. The first change is at 195 plus 36 in your Flight Plan. And it is "Gamma-ray Boom, Deploy, talkback barber pole for about 2 minutes and 40 seconds, then gray, and then to Off. Center position." Over.

195:31:54 Worden: Roger, Joe. Understand. At 195:36:00, "Gamma-ray Beam - Boom, Deploy, talkback barber pole about 2 minutes, 40 seconds, then gray, and switch Off."

195:32:07 Allen: Okay, Al. That's good, and the next two items are deletes over at 196 plus 31. And that is, delete...

195:32:22 Worden: Okay, go ahead.

195:32:23 Allen: ...delete "Map Camera/Laser Experiment Covers," et cetera, and delete "Map Cam Track," et cetera, and at 196 plus 37, delete "Laser Altimeter, On." Over.

195:32:51 Worden: Roger; understand. At 196:30, delete the 2 lines dealing with the Mapping Camera, and at 196:37 delete the Laser Altimeter function.

195:33:12 Allen: Okay, Al, and you're now back on your Flight Plan except for the additional couple of Pan Camera bursts and a Map Camera pass, that you already have copied down. And while I've got you on the line here, I'd like for you to think back yesterday, and I've got a question to ask concerning your suit integrity check. We're trying to go through this and reconstruct exactly what had happened. And I guess what we need is a - a comment about your third suit integrity check. And, that one was the one you did just after the first LM jett had been scrubbed and you went around the back side and did a suit integrity check, and we're wondering if you can recall any of the details of that check for us? Over.

[Before jettisoning the Lunar Module yesterday, the crew had problems getting a good pressure integrity check on their suits and on the forward hatch.]

195:34:27 Gordon: Dave, we're talking about the one you did before the last one, whatever number you call that.

195:34:36 Scott: Yes, Dick, that - that was the one we recycled quickly onboard up here, and it was because we had one of the gloves that wasn't fastened on exactly right.

195:34:52 Allen: Roger, Al. Map Camera and Laser, Off, please.

195:35:02 Worden: Okay, Map Camera and Laser, Off. And, did you understand the comment on the suit integrity check?

195:35:10 Allen: Fine, Al. Thank you. That helps us a lot.

195:35:16 Worden: Okay.

[Long comm break.]

195:39:21 Allen: Pan Camera Power, Off, when convenient, please.

195:39:21 Worden: Okay, it's Off.

195:39:33 Allen: Roger.

[Very long comm break.]

195:52:13 Worden: Okay, Joe; and, we're just sitting here in [the deep space] attitude, all set to dim the lights and do the gegenschein [photography].

195:52:21 Allen: Okay, Al; sounds like fun. Enjoy the back side, and see you in a few minutes. And if there's anything you need from us down here, just give a call.

195:52:35 Worden: Certainly, Joe.

195:52:38 Allen: Knew you would.

[Very long comm break.]

[Endeavour has been maneuvered out of the orb-rate explanation attitude that had the SIM bay continually facing the Moon, to the Deep Space Measurement attitude which is defined with respect to the stars. The spacecraft's motions are given time to damp and Endeavour is allowed to pass into LOS where it is shielded by the Moon's mass from the light of both the Earth and the Sun. The Deep Space Measurement photographs provide a pair of control frames against which the gegenschein frames can be compared. With a 1-minute and a 3-minute exposure done, Endeavour is reoriented to face the Moulton, or L2 Lagrangian point.]

[Flight Plan page 3-308.]

[Once the camera is facing the Moulton point, another two frames are taken with 1-minute and 3-minute exposures. Unfortunately, pre-mission calculations of the attitude they should orient the spacecraft to were incorrect and the photography is unsuccessful. This period of photography should be complete by the time Endeavour commences its 61st revolution at about 196:15 GET.]

[With the gegenschein photography out of the way, Al return the spacecraft to the SIM bay attitude that has the pointy end of the CSM facing forward. This returns the science instruments to an appropriate attitude for sensing the lunar surface.]

196:42:34 Worden: Houston, 15.

196:42:56 Allen: Endeavour, Houston.

196:43:01 Worden: Hello, Houston. Endeavour here.

196:43:05 Allen: Roger, Al. Copy. And I've got a TEI-64 PAD when you're ready.

196:43:19 Worden: Okay, just a minute. [Long pause.]

196:43:39 Worden: Okay, go ahead with the PAD.

196:43:41 Allen: Roger, Alfredo. SPS/G&N for a TEI-64; 36310; plus 0.61, plus 0.92; 204:08:11.62, plus 3011.0, minus 0019.6, plus 0048.8; 180, 102, 002. All the rest NA. Ullage: 4 jet, 12 second. Over.

[An interpretation of the PAD follows:

Purpose: This is another abort PAD for an early return to Earth, with an ignition time right at the end of the 64th orbit around the Moon. Systems: The burn would use the SPS engine under the control of the Guidance & Navigation System.

CSM Weight (Noun 47): 36,310 pounds (16,470 kg).

Pitch and yaw trim (Noun 48): 0.61° and 0.92°.

Time of ignition, T_ig (Noun 33): 204 hours, 8 minutes, 11.62 seconds.

Change in velocity (Noun 81), fps (m/s): x, +3,011.0 (+917.8); y, -19.6 (-6.0); z, +48.8 (+14.9). These velocity components are expressed with respect to the local vertical/local horizontal frame of reference.

Spacecraft attitude: Roll, 180°; Pitch, 102°; Yaw, 2°. The spacecraft attitude for the burn is expressed relative to the lift-off REFSMMAT.

SPS propellants are settled in their tanks by firing the plus-X thrusters on all four quads around the Service Module for 12 seconds.]

196:45:11 Allen: Readback's correct, Al. Thank you.

[Very long comm break.]

[In the meantime, Al should be configuring the Hasselblad EL camera to take a series of images of the lunar maria in ultraviolet light. However, according to the Apollo 15 Index of 70-mm Photographs, no UV photos are taken until the next planned opportunity at 201 hours GET. Yet, the same index ascribes a large amount of photography to this orbit, using the 500-mm lens onto black and white film, and the 250-mm lens onto colour film.]

[The first sequence of photographs on the black and white magazine, mag QQ, are five images taken under high sun conditions of two linear features which run southeast to northwest across the northeastern side of Mare Tranquillitatis. AS15-81-10869 is the first of three images which show Rima Cauchy, a 210-km long rille similar in cross-section to Rima Hadley. The final pair from this area, of which AS15-81-10873 is the best, show the end of Rupes Cauchy, a fault type scarp which runs parallel to and about 50 km south of Rima Cauchy. This fault is about 120 km long and becomes a rille before terminating in the two craters shown in the photograph. The rille and scarp are named after a 12.4-km crater, Cauchy which lies between them, itself named after a French mathematician, Augustin L. Cauchy, 1789-1857.]

[AS15-81-10874 to 10883 are a sequence of ten shots looking at features around the southwestern rim of Mare Serenitatis, just northwest of the crater Sulpicius Gallus. AS15-81-10874 and 10879 are of a bright, diminutive unnamed crater with a classic ray pattern which lies beside the Montes Haemus range. AS15-81-10876, 10881 and AS15-81-10883 are of nearby crater which has a less well-developed ray system though a tongue of dark material is splayed out to one side. This is in an area that, like the valleys at Taurus-Littrow, is noted for the presence of dark mantling. Two touching rilles from the Rimae Sulpicius system are well shown in AS15-81-10877 and AS15-81-10882]

[AS15-81-10884 and 10888 look down into the 10.6-km crater Aratus, a simple bowl-shaped crater with a flat floor and slumped walls. The sequence of photos between and after these two show the landing site, then follow Rima Hadley upstream to its source. AS15-81-10885 and AS15-81-10892 show the plain of Palus Putredinus on either side of Rima Hadley. 10893 to 10897 show the course of the rille to Bela, an arcuate cleft that appears to be the source of the flowing lavas which cut the rille. The ejecta blanket of crater Hadley C, seen in AS15-81-10894, interrupts the path of Hadley Rille by its more recent formation. AS15-81-10899 shows part of the 10-km long Bela with Rima Hadley flowing from it at the top right of the image. To show the full extent of Rima Hadley, from Bela to the landing site, seven of these images have been composited, though readers should note that this is a large image exceeding 1,500 by 1,600 pixels.]

[As Endeavour sweeps out over mare Imbrium, two images, AS15-81-10904 and AS15-81-10905, are taken of one of the most prominent sections of Rimae Archimedes, 100 km southeast of the great crater itself.]

196:58:46 Allen: Endeavour, Houston.

196:58:52 Worden: Hello, Houston; Endeavour. Go ahead.

196:58:54 Allen: Al, could you give us the Mass Spec. Discriminator switch to Low, please.

196:59:03 Worden: Mass Spec. Discriminator to Low.

196:59:05 Allen: Okay, thank you. And did you get a volunteer for [the] eye flash experiment?

196:59:15 Worden: Yes, I think we have a volunteer for you.

196:59:21 Allen: Okay.

196:59:22 Irwin: Your volunteer is checking in here, Joe.

[On three occasions throughout the flight, time is set aside for the analysis of flashes seen within the eye by many lunar travellers. See the journal covering the first light flash experiment in section 7 of the Apollo 15 Flight Journal - Day 3: Flashing Lights; and again starting at 264:26:15 GET for the third light flash experiment in section 23, Science and a Press Conference for accounts of the other two experimental periods. The flashes are believed to be caused by high energy cosmic rays passing through the spacecraft and impinging on the eyeball.]

[On the first occasion, the crew had wanted to use the voice track of the DSE (Data Storage Equipment) to verbally record the characteristics of each flash, giving only a verbal mark on the air/ground comm. As the transcript of this is not in the record, their idea may not have worked although the air/ground information was recovered.]

[Program 20 is controlling the attitude of the spacecraft at the moment with a 5° deadband. Whenever they wish to narrow the deadband, they place the computer mode switch to Free whereby it is no longer driving the RCS, then they enter the figure for the revised size of the deadband before returning the spacecraft's attitude to computer control. This procedure may be to force the computer routines to start from scratch. A deadband of 0.5° is used whenever the SIM bay cameras are operating to ensure accurate pointing.]

[Flight Plan page 3-309.]

197:00:40 Allen: And, Endeavour, you will be interested to know that the impact of Falcon was picked up on three beautiful seismometers on the Moon - a really remarkable record.

197:00:53 Worden: Which ones were they, Joe?

197:00:55 Allen: Apparently, they were the ones from Apollo 12, Apollo 14, and Apollo 15. We haven't had reports from other seismometers yet.

197:01:09 Worden: That's very interesting.

[Of course, there are only three working seismometers on the Moon at this time and well Al knows it.]

197:01:23 Allen: Roger. It went in to within about a degree and in fact, as you know, it doesn't - the exact point isn't all that important. It - it went in just about where we wanted it, though.

197:01:45 Allen: And Al, as soon as you have Noun 79 and you give us Accept, we'll give you state vector. Over.

197:01:57 Worden: Okay, Joe. You have it.

197:01:58 Allen: Roger. We see it. Thank you.

197:02:04 Irwin: Okay, Joe, I'm ready to start the - experiment.

197:02:09 Allen: Okay, Jim, we're copying.

197:02:15 Irwin: Okay. [Long pause.]

197:03:01 Allen: Endeavour, Auto on High Gain, please.

197:03:08 Irwin: Roger. Auto.

[Comm break.]

197:05:12 Worden: Roger, Joe. Understand. Delete the "Pan Camera" lines at 197:04 and 197:09.

197:05:19 Allen: Roger. You can Block the computer but we need a half a degree deadband.

197:05:29 Worden: Roger, Joe. I've loaded it a couple of times. Let me check it again. [Long pause.]

197:06:08 Worden: Okay, Joe. I've got half a degree and - guess I'm having a hard time counting today.

197:06:13 Allen: Thank you, Al. I'm not doing any better.

197:06:18 Worden: Roger.

[Comm break.]

[What Al is actually entering are five digits into the second register of Noun 79. This early computer software is written without routines to handle the decimal point. Therefore, the computer assumes that values are properly scaled before they are entered. The value Al is entering always represents the deadband in hundredths of a degree and he does not enter a decimal point. The difference between entering a 5° and a 0.5° figure is 00500 versus 00050 and it is likely Al simply placed the "5" in the wrong place.]

197:08:31 Allen: Go ahead.

197:08:36 Irwin: As long I'm lying here waiting for a flash, I might comment that Dave and I both observed the flashes while we were - on the surface. While we were in the bunks down there, we observed the flashes with the - oh, about the same frequency as we observed in orbit. One night there was about a 5-, 10-minute period there where I was awake, and I ran a little experiment by just turning over in the bunk. It seemed like the frequency was much less when I was lying on my stomach as opposed to lying on my back. It's just a note of interest.

197:09:18 Allen: Okay, Jim. That's a most interesting comment. And as you know, with about 10 minutes to go during the experiment today, we'll ask for you to turn over and be oriented with your face away from the Moon, and we might very well get the same sort of information this time.

[If the Moon acts as a shield, it would be expected that the radiation causing the flashes would preferentially arrive from one side of the spacecraft when in close lunar orbit. By placing the eyes between the head and the Moon, the head would also act like a shield and further reduce the number of flashes seen. If so, then the frequency of flashes would be expected to increase when Jim turns to face away from the Moon.]

[In VOX mode, a voice-operated switch automatically transmits when Jim talks.]

197:09:57 Worden: Okay, Joe. Go with the PAD.

197:10:00 Allen: Roger. Pan Camera PAD at 197 plus 16 plus 22. And you're to go to Operate per step 5 in your checklist, page S/1-38. And at 197 plus 18 plus 22, the Pan Camera to Standby. And at 197 plus 40, you can delete the P52 scheduled then. Over.

197:10:53 Worden: Roger, Joe. Understand. You want the Pan Camera to - to Operate at 197:16:22 as per the system's checklist 1-38 and to Standby at 197:18:22. And delete the P52 at 197:44 - or - 40.

197:11:13 Allen: Right on, Al. Thank you. And, Jim, we're standing by to copy your comments.

197:11:23 Irwin: Roger, Joe.

197:12:01 Allen: And, Jim, this is Houston. We'd like for you to transmit your description as well as the mark call, please.

197:12:04 Irwin: Understand. [Long pause.]

197:12:39 Irwin: Mark. And it was at the left eye; 8 o'clock, and it was a streak, and it seemed to be moving from 8 o'clock to maybe the 1 o'clock position, about - it covered about 20 degrees of arc out to a position - periphery at 8 o'clock into midway on our sphere of reference. An intensity of three. And...

197:13:13 Irwin: Mark. I just had a flash at 1 o'clock, moving to the center - the center of - moving toward the 12 o'clock position. It was intensity 3 and that last one was the right eye.

197:16:13 Irwin: Mark. A flash at the 12 o'clock, intensity 4.

197:16:25 Irwin: That was right down the plus-X axis, Joe. [Pause.]

[Endeavour is approaching the site where Falcon finally impacted and the Panoramic Camera is taking two minutes worth of pictures.]

197:17:07 Irwin: Mark. A flash at the 8 o'clock, left eye, periphery, intensity 2. [Long pause.]

197:17:38 Allen: Al, Pan Camera Stereo switch to Stereo, please.

197:17:46 Worden: Okay, Stereo it is. [Long pause.]

197:18:28 Worden: And Pan Camera to Standby.

197:18:37 Allen: Okay, Al. Thank you. That might be a super picture.

197:18:28 Worden: Sure hope so, Joe.

[Long comm break.]

197:24:11 Allen: Jim, this is Houston. How are the eye flashes coming?

197:24:17 Irwin: Still waiting, Joe.

197:24:20 Allen: Okay.

[Comm break.]

197:27:17 Irwin: Mark. A streak, at 1 o'clock, moving from the bottom to the top of the - our sphere. Moving - moving definitely vertically up, beginning at 1 o'clock, about three quarters of the way up - intensity 2. [Long pause.]

197:29:58 Allen: Jim, this is Houston. And we're still listening to you. In the meantime, I've got a Map Camera PAD to give to Al when he's ready. Over.

197:30:10 Irwin: Okay, he'll be with you shortly.

197:30:13 Worden: Yeah. Hold on, Joe. We're going over the Harbinger Mountains and right over the Aristarchus Plateau right now. And Dave and I are looking like mad and taking pictures.

[They have good reason to be concentrating on this region as it is one of the most spectacular on the Moon and one to which they will return later in the mission. Aristarchus itself is perhaps the brightest large crater on the near side and is visible with the naked eye, even in the gloom of Earthshine. It was formed about half a billion years ago on a large plateau that is the source of a great many sinuous rilles, large and small. These were cut by flowing lava in much the same way as Hadley Rille was formed, when they fed the expanse of Oceanus Procellarum surrounding the plateau. Often these rilles begin in crater-like bowl-shaped depressions, including the largest, Vallis Schröteri or Schröter's Valley. The landscape around Aristarchus is probably more than six times older than the crater itself.]

[The sequence of photographs that Dave and Al are taking begins with AS15-96-13042. It and AS15-96-13043 are of Rimae Prinz, two rilles just east of the westernmost outcrop of Montes Harbinger. One of these rilles is bisected by an extraordinary depression somewhat like an elongated stadium. This may be a pre-existing crater chain which was flooded by the lavas delivered by the rille. AS15-96-13044 and 13045 show the north rim of the flooded crater Prinz, named after Wilhelm Prinz, 1857-1910, a German selenographer. A small crater just behind that rim, Vera, is the source of another sinuous rille which runs west then north from Prinz. Vera is an example of the many small craters on the Moon that have been assigned arbitrary male or female forenames rather than the more usual name of a deceased scientist. AS15-96-13046 to 13049 have been composited to show the continuation of the rille from Vera until it fades out past the small crater Krieger C. A wider context of these features is given in one of the frames from the Mapping Camera, AS15-2606M]

[AS15-96-13050 is an oblique image of Aristarchus looking roughly north. Note the texture of the surrounding ejecta blanket and how it covers the southern basalt plain in the foreground indicating that the crater is younger than the mare. The terracing or slumping of the wall of this spectacular 40-km diameter, 3-km-deep feature is also well shown. The crater's name comes from the Greek astronomer, Aristarchus of Samos, c. 310-230 B.C.E., who is notable for professing that the Earth rotates on its axis and that it revolves around the Sun.]

[Northwest of Aristarchus, the mighty Vallis Schröteri meanders towards Oceanus Procellarum. The lighting is still too oblique to show much detail although its entire length is photographed in AS15-96-13051 to 13062. The first of this sequence, 13051, shows the source of the rille, the "Cobra's Head", and AS15-96-13052 betrays the existence of an inner rille which loops along the floor of the main feature. A frame from the Mapping Camera, AS15-2610M, shows the rille's course and the crew will photograph it later in the mission once the Sun has risen higher.]

[Scott, from the 1971 Technical Debrief - "I thought the view was spectacular. Every time we came around the corner and had another chance to look at the surface, I saw something entirely new and different."]

[Worden, from the 1971 Technical Debrief - "It was interesting too, from my standpoint. I'd been there for quite a while just looking at the surface go by while you were on the surface. I did the plane change [burn] at 6 hours before rendezvous, and I never had a chance to look at the ground track from the time I did the plane change until after we all got together in the Command Module. It was completely new terrain to me, too (because of the Moon's rotation moving their ground track). We were all sitting there looking at something very new."]

[Scott from the 1971 Technical Debrief - "The terminator is the most interesting part, by far. You can see so much. It is just spectacular. I saw something at Hadley as we went over that was surprising. It's a continuation of the rille into the mountains. As you looked out, it was quite obvious that Hadley Rille was much longer than we had thought before the flight, from the Orbiter photos and the maps. It goes right into the mountains."]

197:30:34 Worden: Okay, Joe. No problem, we're about done.

[Comm break.]

197:33:23 Worden: Houston, 15. Ready to copy the PAD.

197:33:30 Allen: Roger, Al. At 198 plus 25, go to narrow deadband in P20; Verb 22, Noun 79, plus 000.50. Open Cover and Extend Map Camera, per steps 3 and 4 in your checklist. 198 plus 31, Map Camera Image Motion, On. 198 plus 32 plus 10, Map Camera, On; Image Motion, increase, barber pole plus 4 steps; Laser Altimeter, On. 199 plus 19, Image Motion, increase, talkback barber pole. 199 plus 31 plus 56, Map Camera, Off; Laser Altimeter, Off; wait 30 seconds then Map Camera, On - That - that should read, Map Camera, On, to Standby; and then Retract and Close Cover, per steps 7 and 8 in the checklist. And that brings you to 199 plus 31 in your Flight Plan and you can delete the three lines at that point, "Map Camera Image Motion, On; Map Camera, On; Map Camera Image Motion, increase." Over.

197:36:00 Worden: Roger, Houston. Copy. At 198:15, go narrow deadband at P20. Open Mapping Camera Covers and Extend the Mapping Camera. At 198:31 plus 00, Mapping Camera, On. - Oh, I'm sorry, Image Motion, On. And 198 plus 32 plus 10, Mapping Camera, On; Image Motion to barber pole plus 4; and Laser Altimeter, ON. At 199:19:00, Image Motion to barber pole. At 199:31:56, Mapping Camera, Off; Laser, Off; wait 30 seconds, Mapping Camera to Standby - No, that's Retract and Close Covers.

197:36:55 Allen: That's correct, Al; and you can delete those three lines at 199 plus 30. And - there's a note that goes with this. This particular pass will be taken with the Gamma[-ray] experiment and the Mass Spec. experiment booms extended. So don't worry about the fact they're out. One number you gave to me, the first one, should be 198 plus 25, go to narrow deadband. Over.

197:37:28 Worden: Roger. 198:25. That's what I had written. [I] read it wrong.

197:37:32 Allen: Okay, thank you.

197:37:37 Irwin: Okay, Joe. During that conversation, I saw two - both at 8 o'clock. First one was three-quarters of the way out, intensity 2. The last one was at intensity 3, about halfway out, appeared to be at left eye.

197:37:54 Allen: Thank you, Jim; copied.

[Long comm break.]

[Comm break.]

197:46:44 Allen: Roger. [Long pause.]

197:47:30 Irwin: Joe, how is the time going on my one hour?

197:47:33 Allen: Okay, Jim. My sand dial shows about 15 minutes remaining. You'll be going around the corner LOS shortly. We don't have any more instructions for you on the experiment or in fact on anything else going on. We would like your present - a description of your present position in the spacecraft. And, we'd like for you to remain in that position for the rest of the 15 minutes in the experiment. Over.

197:48:04 Irwin: Okay, understand you don't want me to turn over. I'm in the left couch and, of course, facing the plus - plus-X and just when we started that conversation, I had a flash at 11 o'clock on the periphery, intensity 4, and then just the - at the end of your conversation, I had a streak moving from the 3 o'clock to the 9 o'clock, right to left. Right through the plus-X position.

[The Flight Plan instructions called for Jim to sit facing the Moon. He seems to have misinterpreted this as he is in the left couch and is facing towards the apex of the spacecraft, looking along its X-axis. In the current attitude, with the SIM bay facing the surface, this axis and the apex are pointing in the direction of travel, at right angles to the Moon's surface.]

197:48:52 Irwin: Okay.

[Very long comm break.]

[Flight Plan page 3-310.]

[At about 198:15 GET, Endeavour begins its 62nd orbit of the Moon. Soon after, Al reduces the deadband to ½° and begins the period of Mapping Camera photography just read up which begins as the spacecraft crosses the terminator into lunar day.]

[For half an hour, the crew have an exercise period then they continue with some handheld photography of features on the far side, though rather than following the targets suggested in the Flight Plan now, they elect to spread their picture-taking over this and the next orbit.]

[They have two Hasselblad cameras in use, one with black and white film and the long, 500-mm telephoto lens; the other has magazine O with colour film (Ektachrome) and a 250-mm medium telephoto lens. During a sequence of 19 images taken with the latter combination just before AOS, AS15-97-13175 to 13193, they photograph target number 10 as given in the Flight Plan, the ancient 130-km crater Sklodowska. Leading up to this are five images looking towards their northern horizon and across the crater Kondratyuk. With two smaller, but not insubstantial craters on either side of its floor, Kondratyuk straddles across the centre of AS15-97-13177. Before reaching their target, they take an excellent image of an unnamed crater in AS15-97-13180 sited southwest of crater Kovalsky.]

[The next 13 images, AS15-97-13181 to 13193 scan up to and across Sklodowska travelling in a SE-NW direction. Not far away from this feature is the slightly larger crater, Curie, which gives a hint of where the former got its name, for Sklodowska is the maiden name of Marie Curie, 1867-1934, the Polish physicist and chemist who twice won the Nobel prize, first in physics along with her husband Pierre for whom the other crater is named, and then in chemistry. The southeast rim of the crater is seen in AS15-97-13183 including a smaller bowl-shaped that punctures its wall, while AS15-97-13184 brings the double central peak into view. The far, northwest rim is shown in AS15-97-13187. Note the small crater just beyond the rim and the heavily slumped wall where the crater formed. Both these features are well displayed in AS15-97-13188 and it is easy to imagine that the slump could have been caused by the shock of the small crater's impact though this is unlikely judging by the aged appearance of the slump.]

198:41:15 Allen: Hello, Endeavour. This is Houston requesting Reacq and Narrow. [Long pause.]

198:41:50 Allen: Okay, Al, thank you very much. Some time during this pass, we are going to be requesting an ISA [Interim Stowage Assembly] weight which you have in your Lunar Surface Checklist, page 3-2. And we'll have a Map Camera and a Pan Camera PAD to send up to you.

[The ISA was used for stowage in the LM during Dave and Jim's stay on the surface and to carry items from the LM to the CSM.]

198:42:53 Allen: Endeavour, this is Houston. We're showing your Mapping Camera not on at this time and are requesting it on. It may be just to reverify from your 198 plus 32 plus 10 on the Flight Plan. Over.

198:43:15 Worden: Roger, Joe.

[Very long comm break.]

[The photography continues in black and white using magazine QQ and the 500-mm telephoto lens of an unusual, small crater west of the much larger limb crater la Perouse. Two shots are taken, AS15-81-10906 and 10907. This tiny crater is like so many of the other small, flat-bottomed, bowl-shaped craters on the Moon, except for a remarkable slump on one side.]

[Orbital photography returns to the colour camera with 15 frames across northeastern Mare Tranquillitatis of visual target 4, the 12.4-km crater Cauchy and its rilles and scarps. These were also imaged on the previous orbit.]

[The first is AS15-97-13194 which looks NW across the mare towards the target. Cauchy is in the foreground and Rima Cauchy can be seen north of the crater meandering under an almost overhead Sun. AS15-97-13195 is similar but aimed slightly further south to take in Rupes Cauchy, a scarp which becomes a rille at its far end. Cauchy is at the top edge of the frame. It is the major subject of AS15-97-13198 which shows its flat floor and smooth walls. Some slight banding is visible around the top of the crater walls which reflects the layered structure of the mare basalt. The northwestern end of the rille is shown in AS15-97-13199.]

[AS15-97-13200 to 13208 track along Rupes Cauchy. Four of these frames have been composited to show the length covered by these shots. Two small sections of rille are at the left end of the composite.]

[As Endeavour approaches the boundary between Mare Tranquillitatis and Mare Serenitatis, three photographs are taken of Jansen and its environs. Jansen is a flooded crater, 23 kilometres in diameter named after Zacharias Janszoon, 1580-1638, who was a Dutch pioneer of the telescope. The crater is well shown in AS15-97-13210. The slopes show up light coloured in the high sunlight, as do the slopes of Jansen Y, the bright crater inside Jansen. 13211 and 13212 look to the north at Rima Jansen, a sinuous rille. Jansen L is cut off at the corner of 13212.]

[Flight Plan page 3-311.]

[Right on the boundary between the two great mare are craters Dawes and Plinius. Whoever is concentrating on the photography in the spacecraft returns to using the camera with black and white film and the 500-mm lens.]

[AS15-81-10908 and AS15-81-10909 are a spectacular pair looking into the 18-km Dawes lit by a high Sun. Compare this with an earlier frame from the Panoramic Camera, AS15-9562P.]

[The next six images are all of details within Plinius, a classic centre-peak crater, 43 kilometres in diameter. This crater was named after Pliny the Elder, 23-79 AD, whose full name was Gaius Plinius Secundus. Pliny is credited with writing an encyclopedia on natural history which held sway until the middle ages. With the 500-mm lens, the extent of Plinius cannot be captured in one shot. AS15-81-10910 and AS15-81-10913 show the north and south rims respectively. AS15-81-10914 looks down upon the central peak, though this is only distinguishable by the lighter albedo of the slopes.]

199:09:00 Worden: Okay, Joe. Go ahead.

199:09:03 Allen: Okay. In your Flight Plan, at 199:20, you can strike PCM Cable, unless your relativistic speed has managed to lengthen that cable, I guess. At 199:25, you can strike the 3 lines "CMC Mode, Verb 22, and CMC Mode." And, then I have a PAD for you at 200 plus 20, when you're ready.

[On the second day of the flight, the crew had discovered that a PCM cable was missing with only short ones available. The purpose of the cable was to encode the firing of the camera shutter into the spacecraft telemetry.]

199:09:54 Allen: Okay, Al. At this time, it's camera configuration for terminator photos that we missed a little earlier. And the lines should read "CM4/EL/250/VHBW, IVL, f/5.6 at 1/125th, infinity, six frames, Mag Romeo." Over.

199:10:48 Worden: Roger, Joe. Understand. Terminator photo PAD at 200 plus 20 is CM4/EL/250/VHBW, and that's with the intervalometer, IVL, at f/5.6, 1/125th, infinity, six frames and Mag R.

[The photography will be through the right hand rendezvous window using the electric Hasselblad camera fitted with a 250-mm lens. The very high speed black and white film is contained in magazine R. The intent is to photograph the terminator with very low-angle lighting to pick out very subtle details in the shape, or topography, of the landscape.]

[As Joe Allen and Al continue with future plans, the photography is continuing with 4 images taken of Bela, the arcuate feature which is the source of Rima Hadley. Two of these, AS15-81-10918 and 10919 have been composited and show it well though the Sun is high and the features are becoming less distinct.]

199:13:06 Worden: Roger, Joe. At 200 plus 25 open Mapping Camera covers and extend the Mapping Camera. Turn the Image Motion, On, at 275 - 200:27:56, EL On, and at 29:36, EL Off. At 30:36 Mapping Camera, On; Image Motion to barber pole, plus four; and Laser, On. And then Pan Camera, Standby, Power, On; Stereo, Exposure, normal.

199:13:41 Allen: That's correct, Al. And continuing on through a few more steps here, and I'll read them all, and then stand by for your readback. 200 plus 33 plus 29, Pan Camera, Mode to Operate. 200 plus 49 plus 32, Pan Camera to Mono. 200 plus 54 plus 27, Pan Camera, Stereo. 200 plus 59 plus 22, Pan Camera, Mode, Standby; Pan Camera, Power to Off on MSFN cue. And, moving right along, 201 plus 17 plus 00, Pan Camera, Image Motion, Increase. I'm sorry, Al. That was misread. That should be Map Camera, Image Motion to Increase; talkback barber pole. 201 plus 28 plus 21, EL On. 201 plus 30 plus 01, EL Off. 201 plus 30 plus 21, Map Camera, off; Laser Altimeter, Off. And the final one, 201 plus 32 plus 00, retract camera and close covers per the page in your checklist. Over.

199:16:27 Worden: Roger, Joe. Understand at 201:17:00, Mapping Camera, Image Motion, Increase to barber pole; at 201:28:21, EL On; at 201:30:01, EL Off; 201:32:00, Off. No, back to 30:01, after EL Off, read Map Camera, Off; Laser, Off. And, at 201:32:00, Retract and close the Mapping Camera covers.

199:17:08 Allen: Okay, Al. And read back to me 4 more lines, beginning with 200 plus 33 plus 29. You didn't go back quite far enough, and that - that one should read Pan Camera, Mode to Operate.

199:17:24 Worden: Oh, okay.

199:17:25 Allen: And I'm standing by.

199:17:26 Worden: Roger. At - at 33 - at 200:33:29, Pan Camera to Operate. At 49:32, Pan Camera to Mono. At 54:27, Pan to Stereo. And, at 59:22 Pan to Standby; Power, Off, on MSFN cue.

199:18:00 Allen: Okay, Al. Sounds real good. But double check for me one line, which I may have goofed. It's the 201 plus 30 plus 21, Map Camera, Off; Laser Altimeter, Off.

199:18:20 Worden: Roger, Joe. Understand. At 201:30:21, that's 20 seconds after EL Off, we get the Mapping Camera, Off and the Laser, Off.

199:18:33 Allen: Yes sir, that's affirmative. And, I guess - we're still waiting for an ISA weight. Other than that, we're doing real fine.

199:18:47 Worden: Okay, Joe. [Long pause.]

199:19:10 Worden: Houston, 15.

199:19:11 Allen: Go. Go ahead, Al. And, we're waiting for a Image Motion talkback to barber pole.

199:19:28 Worden: Okay. Dave's going to get the ISA weight out for you and call you.

199:19:33 Allen: Okay. If he's able to weigh it right there, I'd like to know how he's going to do it. I assume he's got it written down, though.

[Of course Dave cannot "weigh" the ISA in the spacecraft as he is in a weightless environment. On the Earth, or as they do on the Moon, the force acting upon an object due to the gravity field it is in can be measured by having it act on a calibrated spring. This gives the weight for the object in that particular gravity field.]

[Though they are near the Moon, they are in freefall around it and the force of gravity is exactly counterbalanced by the centrifugal force of their path. This makes them weightless. How might the mass of an object be determined in this environment? One way would be to use the object's inertia. Set the object in motion in the spacecraft at a known speed and measure the force it applies when it is brought to a halt. Similar to this would be to spin it around on the end of a string or pole at a known rotational rate and measure the force on the string. The distance from the centre of rotation to the object's centre of mass would also have to be known.]

[Long comm break.]

199:22:50 Allen: Go ahead, 15.

199:22:56 Irwin: Yes, Joe. I have weight information on the ISA. The ISA total was 64 pounds, which includes bags 4 and 6, and 8 pounds return items. And the ISA, by itself, without anything loaded in it, was 8 pounds. Over.

199:23:19 Allen: Okay, Jim, copied that. Sounds like there might be a stone or two in there.

199:23:29 Irwin: Yeah. Bags 4 and 6, for sure.

199:23:38 Allen: Thank you, Jim.

[Long comm break.]

[Joe Allen is replaced at the CapCom console by Robert Parker.]

199:28:58 Scott: Roger, Dr. Parker. Shield, On. [Long pause.]

199:29:48 Parker: And, 15. Time to start the terminator [photography] now.

199:29:54 Scott: Roger.

[Comm break.]

[Endeavour is about to cross the terminator and the current period of Mapping Camera photography will soon stop. Before it does, a sequence of photographs are taken with the Hasselblad on high speed film of the northwest corner of the Aristarchus Plateau. The sequence extends from AS15-98-13327 to 13335.]

[Of note among these is AS15-98-13329 which shows the old, heavily cratered surface of the plateau along the bottom of the shot. Bottom left is Raman, an 11-km crater at the western apex of the plateau named for the Indian physicist Chandrasekhara V. Raman, 1888-1970. Running along the upper third of the picture is the Montes Agricola mountain chain which extends for about 160 kilometres parallel to the northwestern edge of the plateau and about 40 km offshore. Note the apparent shoreline around the mountain spur on the right. This feature will be seen clearer on the next orbit when it is recognisable as a rille which temporarily runs along the base of the hill. Georgius Agricola, 1494-1555, was a German naturalist and physician.]

[Seen here in a scan presented by Kipp Teague, AS15-98-13331 reaches the terminator itself. The southwestern end of Montes Agricola is along the lower third and a part of a wrinkle ridge system, Dorsa Burnet, runs north-south to its left. The ridge is named after an English naturalist, Thomas Burnet, 1635-1715. Looking at images like this, it is easy to imagine how pre-space-age illustrators of the lunar surface came away with the notion that lunar hills were extremely jagged. The terminator has always been attractive to telescopic observers of the Moon and this is where vertical scale is exaggerated. The penultimate image in this sequence, AS15-98-13334, shows the sunlight catching the raised rims of the craters and the peaks of the wrinkle ridges.]

199:32:13 Scott: Roger. Standby. [Long pause.]

199:32:49 Parker: Laser Altimeter, Off, please.

[Comm break.]

[Parker is referring back to problems the crew had in obtaining a good pressure integrity check yesterday at 177:56:39 prior to jettison of the LM.]

199:34:41 Parker: And Auto on High Gain [Antenna], please.

199:34:46 Scott: Auto. [Long pause.]

199:35:02 Scott: Houston, 15. Go.

199:35:09 Parker: 15. Two questions we'd like to ask. First one's specific, and that is, if you noticed anything about the connector between the LCG and the suit when you took it out in order to put the plugs in yesterday afternoon. Was it already out? Was it loose? Was it not lock - locked? Or what? And secondly, a general question building up from this. Can you tell us anything - any insights you acquired in taking the suits off and looking at the connector or just, in general, about what this problem may have been caused by?

199:35:51 Scott: Well, I guess - I guess our first indication was lack of a good integrity check. As a matter of fact, we couldn't get much more than about a pound in the suit. And the first - In thinking it over, we - we thought the only thing it could be would be those connectors, because that was the on - only semi-open port, even though it shouldn't - shouldn't be leaking. And, everybody checked their helmet and gloves and they appeared to be locked, so we broke open the helmet and gloves and Jim reached in through my zipper and pulled out the LCG connector and stuck in the plug. And then we rezipped, or I did. Jim rezipped me. And we tried another integrity check, and it worked okay. I guess beyond that - I don't have any explanation for it, other than the only possibility is that the LCG connector was leaking, or that somebody's glove or helmet was leaking, because the suits have been, as you know, very tight all the way through.

199:36:55 Parker: Roger. Did Jim notice when you - when Jim took out your connector there, to put the plug in, did he notice it as being loose, unattached, or not lock-locked? Did he have any - could he tell any of that just reaching in with his fingers?

199:37:15 Irwin: Bob, this is Jim. The lock-lock was engaged on that water connector on Dave's suit.

199:37:22 Parker: Okay, copy. And do we understand that Dave's suit was the only one that did not pass the integrity check that first time around?

199:37:32 Irwin: No. You can't isolate it. The whole suit circuit is the integrity check. It's spacecraft plus three suits. So, there's no way to tell.

199:37:40 Parker: Roger. But on - what I mean is that you did not put - did you put plugs in Jim's suit, too, or just in Dave's suit?

199:37:50 Irwin: No, only - only in one suit. But we did go through the operation of taking off helmets and gloves, which also may have been the problem.

199:37:57 Parker: Roger. Copy that.

199:38:02 Irwin: In - in other words, there may have - even though we checked the lock-locks on the helmets and gloves, why, somebody could have had a cocked one and - and missed it. These - es - especially the - the surface equipment was - had an - an awful lot of lunar dust on it, and it was sort of hard to work. We're - we're going to get them cleaned up before the EVA, but after three runs down there, why, the connectors were getting pretty tough to work, even though we did lubricate them.

199:38:31 Parker: Roger. Copy. I don't think we have anything else, Dave. We noticed you did seem to have some trouble getting a suit integrity check the second time around, also. Is that right?

199:38:48 Scott: Yes. There was a glove that wasn't locked.

199:38:51 Parker: Okay, guess that was on the loop. Thanks.

199:39:09 Scott: I think the suit circuit's tight. I think that just might have just been one of those things, because the last one we ran was real good. It - the flow dropped down to like 6 or 7 tenths, I guess, and it would have stayed there all day long. I think we've got a good suit loop, but - I'm not worried about that at all. Just a matter of getting all the connectors cleaned up so they all work well. And ensuring that everybody gets a good lock-lock.

199:39:35 Parker: Roger, Dave. We agree too. I - it seems to us that that sounds like it was just one of those situations we run a suit integrity check for.

199:39:45 Scott: Roger. That's exactly right.

[Very long comm break.]

199:49:49 Parker: And, 15; Houston. You are Go for LOS.

199:49:57 Scott: Thank you very much, Houston.

[Very long comm break.]

[Flight Plan page 3-312.]

[The 63rd orbit of Apollo 15 commences at about 200:12 GET. This far-side pass is a quiet one for the crew. The spacecraft is flying pointy-end first in what is called the "+X Forward SIM Attitude" which has the SIM bay facing the Moon. All the major instruments are operating, Gamma-ray, X-ray, Alpha Particle and Mass Spectrometers. Note that in this attitude, the inlet to the Mass Spectrometer is not facing the direction of travel so native atoms from the lunar atmosphere are not being selectively sampled.]

[Once again, as they reach the terminator, the Mapping Camera will be brought into use to photograph the daylit side. In preparation for this, both of the experiment booms are retracted and while the Gamma-ray instrument is kept powered, the Mass Spectrometer is switched off. The Panoramic Camera is also brought into play three minutes before AOS for nearly half an hour, taking 224 frames in all, most of them in stereo. Handheld photography during the coming revolution will be even more intensive than the last.]

[As seen from Earth, the Moon is approaching full. Most of their far-side passes are in darkness while most of their near-side passes are in sunlight. According to the Apollo 15 Index of 70-mm Photographs, the crew use four different camera magazines during the coming near-side pass, taking 124 photographs on black and white, very high speed black and white, colour and ultraviolet sensitive film.]

[The photography begins with images of a small crater right on the rim of the 77-km crater Gibbs at the Moon's eastern limb. AS15-90-12267 and 12268 are taken with the relatively wide-angle 60-mm lens while AS15-81-10920 uses the 500-mm to show it's detail. The eastern rim of Gibbs runs from top-left to bottom-centre. Unlike most small, fresh craters, this one displays dark ejecta excavated from the larger crater's rim.]

[An unusual crater with a one-sided slump, first discussed after 198:43:15, is revisited in AS15-81-10922, while 10923 spots another small crater within the floor of the larger 78-km la Perouse.]

[When the 500-mm lens is trained towards the horizon, the result is, in the opinion of this author (Woods) a quite breathtaking portrayal of the Moon's forbidding, desolate beauty as depicted in AS15-81-10924. The picture looks NNW past Maclaurin, the east rim of which is visible in the foreground. Colin Maclaurin was a professor of mathematics in Aberdeen and Edinburgh in Scotland, and lived 1698-1746. The dark, simple crater just below and right of centre is unnamed. Along the bottom-centre is the eastern rim of Mare Spumans (The Foaming Sea) and right of centre, we can see across a light-coloured crater which is Pomortsev, formerly Dubiago P, which has been named after Mikhail Pomortsev, 1851-1916, a pioneer of rocket propulsion from Russia.]

200:46:21 Worden: Hello, Houston; this is Endeavour.

200:46:24 Parker: Roger. We got the usual Flight Plan updates, if you'll get a Flight Plan out and copy them in, please.

200:46:37 Worden: Okay; stand by one.

200:46:39 Parker: Okay; and if someone could give us High Gain Antenna to Auto, we'd appreciate it.

200:46:59 Worden: Go ahead with the update.

200:47:00 Parker: Okay. First one is the UV photo plan - PAD at 201:05 in the Flight Plan. The T-start will be 201:11:19. Over.

200:47:17 Worden: Understand. UV T-start 201:11:19.

200:47:22 Parker: Roger. Next, at 201:20, we will delete "PCM cable."

200:47:35 Worden: Okay; got that.

200:47:37 Parker: Roger. At 202:30, it's Discriminator, Low, in that line on the Mass Spec.

200:47:52 Worden: Okay. Discriminator, Low, at 202:30.

200:47:56 Parker: Roger. At 203:21, we will delete "Laser Altimeter, Off."

200:48:11 Worden: Understand. Delete "Laser Altimeter, Off" at 203:21, and let's hold up on the rest for now.

200:48:47 Parker: And 15, 30 seconds to Pan Camera, Mono.

200:49:05 Scott: Hey, go with the rest of the updates, Bob.

200:49:08 Parker: Okay. At 203:23, we'll delete the "Mapping Camera Track, Retract, talkback barber pole, 4 minutes, gray then Off, center;" that whole line.

200:49:37 Scott: Okay; that's deleted. Next.

200:49:44 Parker: And we want Pan Camera, Mono, please.

200:49:55 Scott: It's there.

200:49:57 Parker: Roger; sorry.

[According to the Flight Plan, the time when the Panoramic Camera is switched to Mono is also when they should be taking Hasselblad photos of a point on Mare Fecunditatis where the Soviet probe, Luna 16, landed in September 1970. This spacecraft is notable for having been the first successful sample return mission mounted by the Soviets bringing back 0.1 kg of dust in a 35-cm core. A high quality suite of photographs, both by the Mapping Camera and the onboard cameras, will help in determining the context of the returned samples. The crew do eventually photograph this site extensively during rev 69.]

[Just now, they are taking ultraviolet photographs of the landscape north of one of the most prominent craters on the eastern side of the Moon's disc, Langrenus, a classic 132-km feature with heavily terraced walls and a dominant central peak. Michel Florent van Langren, c. 1600-1675, was a Belgian who produced one of the earliest maps of the Moon with named features, yet the only name which has survived from that map is for the great crater which he named after himself. This UV photography may be a replacement for the photography missed at 196:56:19, though that was intended to look at a mare area whereas these photographs are of the Langrenus ejecta blanket.]

[In this sequence, ranging from AS15-99-13457 to 13466, ten shots are taken, two each through UV filters 4, 1, 2 and 3 with a final pair taken through filter 4. Though these are intended to be analysed from the point of view of their filter characteristics, the two most interesting from a visual standpoint are from filter 4. AS15-99-13458 shows the north rim of Langrenus with the 13-km Acosta just beyond. Acosta, formerly Langrenus C gets its name from Cristobal Acosta, 1515-1580, a physician from Portugal. Along the top left, the rim of Atwood is just visible. The 29-km Atwood, named for a British mathematician and physicist, 1745-1807, is one of a triplet of craters, better seen in AS15-99-13465 which have recently been renamed from their previous alphabetic designations with respect to Langrenus. Atwood was formerly Langrenus K while in the centre of 13465 is Naonobu, formerly Langrenus B, a 35-km crater which, like Atwood, is heavily degraded and which was named after Ajima Naonobu, 1732-1798, a mathematician from Japan. The largest of this trio is the 43-km Bilharz which is partially cut off on the left of 13465. It was named after a German physician, 1825-1862.]

[Three images are presented here from the current Panoramic Camera sequence taken as the spacecraft coasts over Sinus Successus and Mare Fecunditatis (with thanks to journal contributor Robin Wheeler who scanned and donated them). Frame AS15-0112P consists of a sweep that runs from Sinus Successus to the centre of Mare Fecunditatis in the region of Lindbergh (1902-1974