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Solo Orbital Operations - 2	Journal Home Page	Solo Orbital Operations - 4

Apollo 15

Solo Orbital Operations - 3

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

[This section primarily covers August 1, 1971, the seventh day of the Apollo 15 mission.]

[The last communication with Al Worden and Mission Control in Houston, Texas, was at 134:04:04, although Al's 7 hour rest period began 45 minutes earlier.]

[Endeavour is orbiting the Moon once every two hours and is flying with the SPS (Service Propulsion System) engine facing the direction of travel. This allows the inlet of the Mass Spectrometer to face into any lunar atmosphere and gather its constituent molecules. Other instruments operating during the rest period are the Gamma-ray Spectrometer, the Alpha Particle Spectrometer and the adjacent X-ray Spectrometer]

[The plane of the spacecraft's orbit is inclined 26° to the lunar equator because Endeavour was delivering the Lunar Module to a site at that latitude. Strictly speaking, since the orbit is retrograde, that is, opposite the direction the Moon is rotating, we should say that the orbit's inclination is 180 - 26 = 154°. 38 hours ago, Al carried out the circularisation maneuver which essentially defined his present orbit. Since that time, the Moon has rotated just over 21° underneath the plane of Endeavour's orbit and is taking Al over fresh territory. In the same period, the terminator has moved through 19½°, revealing much of the centre of Mare Imbrium for the first time.]

[CSM Flight Plan pages 3-191, 3-193, 3-195, 3-197, 3-199 and current page, 3-201.]

[The Flight plan defines the end of the rest period as 140:30 and that is exactly when CapCom Karl Henize sends the wake-up call.]

140:31:11 Henize: Good morning, Al. They tell me you're sleeping very well right now; I'm sorry to wake you up. [No answer.]

140:32:08 Henize: Good morning, Al. On the planet Earth, August the first is creeping in upon us, and your bleary eyed Flight - CapCom down here is standing by at your service. [Long pause.]

140:33:25 Worden: Hello, Houston. Endeavour.

140:33:28 Henize: Hello, Endeavour. Good morning. How are you doing?

140:33:35 Worden: Well, other than being rudely awakened, I'm doing fine, Karl.

140:33:39 Henize: Hey, I'm sorry that I have to do that, Al. Sounded like you were sleeping good. Hey, as the first step, can you give us High Gain [Antenna], Auto, and give us Accept for a state vector?

140:33:55 Worden: Okay, Karl. You've got them both.

[Less than four minutes after his wake up call and Mission Control already have Al busy. This morning, first tasks from the Flight Plan are to complete his post sleep checklist while Mission Control uplinks a new state vector into the guidance system. Al sets the computer to receive it. The consumables will be checked and Al will write down some Flight Plan updates and up coming photographic tasks.]

[Flight Plan updates are usually one of the first things Mission Control deals with in the morning as the overnight team has had plenty of time to think about what needs to be done.]

[The term PAD, used quite liberally throughout the Apollo missions, stands for Pre-Advisory Data and simply refers to any information which the crew will need for a particular operation, whether it be taking photographs of some interesting feature or igniting the SPS engine for a return to Earth.]

140:34:42 Henize: Okay. On the Flight Plan update at 141:03, they simply want you to add the report on the Gamma-ray and Mass Spec boom Delta-T's. And at 141:04 there is a "Laser Altimeter, On," which should be transferred down to 141:15. Those numbers come through okay?

140:35:30 Worden: Roger, Karl. I got you. At 141:03 you want me to report the Delta-T's on the retract for the boom; and move the "Laser Altimeter, On" to 141:15.

[Just before Al's rest period, at 130:28:01, Mission Control reported that the Laser Altimeter was showing signs of failing and it was switched off early. They may want to delay powering it up until nearer the time the Mapping Camera comes on to preserve its life.]

[Also, Mission Control want Al to report to them the times he measures for the retraction of the two booms which carry the Gamma-ray and Mass Spectrometers rather than just record them on his paperwork.]

140:36:09 Worden: Roger. Let's have them.

140:36:11 Henize: Okay. Camera configuration. CM/EL/250/CEX, f/5.6, 1/250, infinity; 15 frames. And at 142:04, the actual [time to] execute [the photography]: photo target 25; A12, A13-P25. And, it says CM with window 3, with the same - with the same camera configuration: f/5.6, 1/250th at infinity; and 15 frames at 10 second intervals. Right. And this is magazine Q, pardon me. So much for the short Flight Plan update. Did the photo target 25 stuff come through okay?

140:37:38 Worden: I think I got most of it. But let me read it back to you just in case. Okay, at 141:55, that would be: set up cameras for photo target 25, at CM/EL/250/CEX, f/5.6, 1/250 at infinity, 15 frames; and then at 142:04 at A12, A13, photo target 25. CM, 3; and the settings going to be for 15 frames at 20 seconds from Mag Q.

140:38:18 Henize: Okay, everything's right except 15 frames at 10 second intervals - one zero.

140:38:28 Worden: Ah, so. Okay, 15 frames at 10 seconds.

[The photography shorthand should have said 'CM3' to indicate that window 3, the hatch window, is to be used and Karl Henize corrected himself. The shorthand decoded means use the Hasselblad EL camera with a 250-mm lens and daylight colour Ektachrome film through window 3 of the Command Module. Exposure should be 1/250th of a second with a lens aperture of f/5.6, and the subject is photo target number 25.]

[Mission Control has finished uploading a revised state vector into the computer and so Al can begin using it again.]

140:38:53 Worden: All right, go ahead.

140:38:54 Henize: ...okay. The Mapping Camera Photo PAD starts 141:17:26; [and stops] 144:09:30. And right down below is the Pan Camera PAD, [starts] 141:46:11; [stops] 142:01:31. And as a part of this, just across the page there, at 141:45, we would like to move down that statement, "Mapping Camera Image Motion, Increase;" move that down to 57 - 141:57. And that's all.

140:39:50 Worden: Roger. Understand. The Mapping Camera photo PAD is, 141:17:26; 144:09:30. The Pan Camera photo PAD is 141:46:11; 142:01:31. And move the "Mapping Camera Motion Increase to talkback, barber pole" from 141:45 to 141:57.

140:40:18 Henize: That's excellent. I - I also have science report, which you can probably pick up on the next rev, and consumables report. And I guess we would like a status report from you. We could either do that now or early in the next rev. How do you feel about it?

140:40:49 Worden: Oh, I can give you the status report now, I think, Karl. Stand by one. [Pause.]

140:41:08 Worden: Okay, Karl, I guess - crew status report: Got 6 hours sleep all in one period, and very good night's sleep, I might add; and my PR - no medication, and my PRD [Personal Radiation Dosimeter] is 23149.

140:41:37 Henize: Roger. 23149.

140:41:46 Worden: And standby for the consumables. [Long pause.]

140:42:06 Henize: What was that comment on consumables? Would you like to copy them now?

140:42:14 Worden: Roger, Karl. Might as well get them now.

140:42:16 Henize: Okay. The time is 140 hours; RCS total is, 61 [percent]; quad A, 61; [B] 61; [C] 59; [D] 61; H₂ tanks, 70, 70, 48; O₂ tanks, 75, 78, 60.

140:42:47 Worden: Roger, Karl. 140:00, RCS total 61, it'd be 61; 61; 59; 61; H₂ tanks, 70, 70, 48; O₂ tanks, 75, 78, 60.

140:43:07 Henize: That's correct. We - and, they say that they would like to have you do the configuring of the DSE that comes up there at 141:35. And if you can listen for another minute I've got an EECOM status if you'd like.

140:43:39 Worden: Roger. Go ahead. I'll be doing a P52.

[As on every far-side pass, the DSE (Data Storage Equipment) records spacecraft telemetry and SIM bay science data for subsequent replay to the ground on the following front side pass. Normally, the commands to operate the recorder come from Mission Control but here they are asking Al to set it up for them prior to LOS. The P52 platform realignment is, as usual, using option 3, based on the orientation of the landing site. Before starting it, Al places the CMC Mode switch to "Free" to stop the RCS (Reaction Control System) unexpectedly moving the spacecraft.]

140:44:16 Worden: Well, that certainly sounds very good, Karl. [Long pause.]

[Based on spacecraft voltage on the main supply buses of 28 volts, the average power consumption, given by P = V × A, is 28 × 80 = 2.24 kilowatts.]

140:44:44 Worden: Roger, Karl.

[Al has much to do before mealtime, both during this far-side pass and the subsequent near-side pass. With the CMC Mode switch set to "Auto" and the spacecraft's attitude under RCS control again, he rolls clockwise 40° This roll is done prior to turning the spacecraft around so as to avoid the guidance system getting into the gimbal lock condition.]

[CSM Flight Plan page 3-203.]

[As Endeavour approaches the transition from lunar night to day, Al prepares for a period of photography using the cameras in the SIM bay and his Hasselblad. The spacecraft's attitude is changed to point the sharp end of the Command Module in the direction of travel by changing the omicron value in Noun 78 to 180°. The SIM bay will still be aimed at the Moon before and after this maneuver. The Mass Spectrometer comes off while the Laser Altimeter comes on and the booms are retracted. Al will be monitoring the times taken for the booms to retract in view of problems he has already had with the Mass Spectrometer's boom. Endeavour begins its 33rd revolution around the Moon at about 141:08. Soon after, as the spacecraft enters the sunlight, he will narrow the limits of the spacecraft's attitude drift to a half degree deadband and commence Mapping Camera photography. Mission Control will soon find that this narrow deadband is causing the thrusters to fire more than expected and will talk to Al about this at 142:10:03.]

141:37:52 Worden: Houston, Endeavour. Read you loud and clear.

141:37:57 Henize: Very good. [Long pause.]

141:38:34 Worden: And, Karl, Endeavour. I've got a message for our friends this morning.

141:38:39 Henize: Go ahead, Endeavour.

141:38:43 Worden: Okay. If the King is there: Mar-hah-bah al el-arde in-Endeavour ee-lay-kum sa-lam.

141:38:54 Henize: Beautiful. If he's not down there listening, I'll make sure it gets relayed to him, if I can remember.

[Al's message is intended for Farouk El-Baz, an Egyptian who, by way of Bellcomm, Inc., a think-tank hired by NASA, had come into the site selection process and, for the later Apollo flights, was pivotal in training the CM pilots to become observers of lunar geology from orbit. El-Baz had sifted through all the Lunar Orbiter imagery taken in 1966 - 67, and classified every feature he saw, in the process becoming an expert on lunar landforms. Through his teaching, he passed on his enthusiasm to the astronauts who nicknamed him 'the King'. Al's message, which is Arabic, translates as "Hello Earth, Greetings from Endeavour." and is one of the nine versions phonetically written down on a piece of paper for Al by El-Baz. This greeting became the title of a book of poetry which Al wrote after the mission.]

141:39:13 Henize: We're ready to copy.

141:39:17 Worden: Okay. Stars used were 01 and 36; Noun 05 was plus four balls 1; Noun 93 was minus 00.004, minus 00.050, plus 00.041. They were torqued at 140:49:00.

[To translate the torquing data: Stars 01 (Alpheratz, the brightest star in Andromeda) and 36 (Vega, Lyra's most prominent star) were used to realign the platform. Al's accuracy in measuring the angle between the two stars, a good guide to the accuracy of his sightings, was 0.01° and each of the gimbals, X, Y and Z were moved, or torqued, by -0.004°, -0.05° and +0.041° respectively.]

141:40:10 Worden: Roger. And then I'll get back with you on the Delta-T [for the boom retraction].

[This is the start of a ten minute period when a system within the Gamma-ray Spectrometer for discriminating between genuine gamma-ray and other cosmic-ray events is switched off for calibration purposes.]

141:40:21 Worden: Okay. The shield is off and the Delta-Ts, the Mapping Camera extension was 3 plus 50; the Gamma-ray retracts was 3 plus 12; and unfortunately the Mass Spectrometer boom, when I go to Retract, even now, I get a barber pole. It never did go gray.

141:40:56 Henize: We copy, and we're sorry to hear that.

141:41:02 Worden: Although, I'm not so sure but what part of our problem is not in the talkback indicator itself. After 3 - well, 3 to 4 minutes, I was watching the talkback and saw no change, so I went to Extend and noticed that the talkback jumped about half position in the window. So apparently what's happening is that the talkback is - is not triggering before gray. It's going about half way. There's about a half a barber pole in the window and, if I go to Extension, I get full barber pole. So that may indicate that it's just a talkback problem.

141:41:48 Henize: Roger. We copy.

141:41:58 Worden: I don't know whether you understand all that or not. But...

141:42:02 Henize: I'm not sure...

141:42:03 Worden: ...I sort of feel like maybe there's a talkback problem.

141:42:07 Henize: Right. Incidentally, how many times did you cycle the switch on the deploy retract.

141:42:16 Worden: Oh, I guess I probably cycled it 3 or 4 times.

141:42:20 Henize: Okay. I guess the reason I asked is I think we have a suspicion there that we have the - that cable not coiling correctly and recycling may - feed the coils correctly and solve the problem.

141:42:46 Worden: Okay. I'll go ahead and deploy and retract it. I'll cycle it a - a few times here and see if I can get [it] to come in. [Long pause.]

[Worden, from the 1971 Technical Debrief - "At the first part of the lunar orbit activities, the Mass Spectrometer was deployed and retracted almost as I had anticipated, knowing the approximate times the boom should take to deploy and retract. Those times came out very close. Only along towards the end of the lunar-orbit activities did I start to see those times varying. In fact, at one point, the Mass Spectrometer failed to retract. I never did get a gray indication. I turned it off, turned the retract mechanism off, and extended and retracted the Mass Spectrometer in short bursts, cycling it until I got a gray indication. This meant that the Mass Spectrometer was very close to being fully retracted, but yet something was holding it from the final retraction. Looking in the Flight Plan, I noticed that the first time I saw a problem with the Mass Spectrometer boom was at approximately 119 hours and 20 minutes in the flight, when I got no retract on the Mass Spec boom. At that time, I had retracted the boom and waited approximately 2½ minutes and then started watching the talkback, expecting it to go gray so that I could turn the switch off. Instead of going gray, it went to a half barber pole; the gray shutter in the talkback dropped about halfway, and it stayed there. I cycled it to extend three or four times, maybe bursts of 5 or 6 seconds, and then to retract. And after about the third cycle, the talk-back went gray, indicating that it had fully retracted. I ought to clarify the operation of the talkback. On all the extensions, the talkback was full barber pole until the boom was extended, at which time it went gray. On the retraction, it was full barber pole until the nominal time for full retraction had elapsed, at which time the talkback went to half barber pole. That was the only time, on that last bit of the retraction, when there was anything unusual about the operation of the talkback."]

[Henize, from the 1971 Technical Debrief - "Did you ever notice a half barber pole in later retractions? We never heard anything more about it."]

[Worden, from the 1971 Technical Debrief - "Yes. On each succeeding retraction, after that first one, the Mass Spec boom operated exactly the same way. I always got the half barber pole. After 4 or 5 cycles, for a considerable amount of time at least, I could always get the gray indication. Along towards the end, it finally got to the point where I never could get full retraction on the Mass Spec boom. In fact, during the EVA, we had cycled the boom to extend and retract on the short cycles several times. I never could get a gray, and when I looked at it during the EVA, the cover was tilted about 30 degrees on the hinge, and the guide pins in the Mass Spec were just barely coming through the guide slots. It was on the guide rails, but the pins weren't fully extended through the guide slots."]

[From the 1971 Mission Report, - "The Mass Spectrometer boom did not fully retract on five of twelve occasions. Data analysis, supported by the crew debriefing, indicates that the boom probably retracted to within about 1 inch of full retraction. Cold soaking of the deployed boom and/or cable harness preceded each anomalous retraction. In each case, the boom retracted fully after warmup."]

[From the 1971 Mission Report, - "The deploy/retract talkback indicator is normally gray when off, when the boom is fully retracted, or when it is fully extended. The indicator is barber pole when the boom is extending or retracting, and will show half barber pole if the drive motor stalls. The crew noted this last condition on the incomplete retractions."]

[From the 1971 Mission Report, - "An inflight test of the Apollo 15 boom indicated that the problem was a function of temperature. Testing and examination of the Apollo 16 spacecraft showed that the failure was possibly caused by pinching of the cable harness during the last several inches of boom retraction. The cable could have been pinched between the bell housing and rear H-frame bearing, or a cable harness loop was jammed by a boom alignment finger against the bell housing."]

[From the 1971 Mission Report, - "The Mass Spectrometer boom mechanism was qualified by similarity to the Gamma-ray boom mechanism. There are significant differences between the two designs and they are:

1. When extended, the Mass Spectrometer boom is 1 foot 10 inches shorter than the Gamma-ray Spectrometer boom.
2. The Mass Spectrometer cable harness contains 6 more wires and, therefore, is larger in cross section than the Gamma-ray Spectrometer cable. In addition, the harness coil diameter on the Mass Spectrometer is ½ inch larger (6.7 inches compared to 6.2 inches).
3. The Mass Spectrometer cable harness terminates with an in-line connector; whereas, the Gamma-ray Spectrometer harness terminates with a 90 degree connector.
4. The Mass Spectrometer rear H-frame bearings retract past the lip of the bell housing; whereas, the retracted bearing position for the Gamma-ray experiment boom is even with the bell housing lip. Therefore, the lip on the sides of the Mass Spectrometer bell housing is relieved about ½ inch for bearing clearance."]

[From the 1971 Mission Report, - "The differences between the two configurations are now considered to be significant enough to have required separate testing for the Mass Spectrometer boom assembly. Accordingly, a delta qualification test will be instituted and a thermal vacuum environmental acceptance test will be performed on each flight unit."]

141:43:35 Worden: Roger.

[Comm break.]

[This is the modified T-start time read up to Al at 140:38:54. The Panoramic Camera will operate for about 15 minutes. During this time, the only instrument in the SIM bay not operating is the Mass Spectrometer.]

141:45:50 Worden: Roger, Karl. Right with you. [Long pause.]

141:46:25 Henize: Al, we'd like to have High Gain Antenna, Auto, now.

141:46:32 Worden: Auto.

[Comm break.]

[Included in the current Mapping Camera pass is this image, AS15-1113M, which has the future Apollo 17 landing site near the centre.

Mare Tranquillitatis is to the south and Mare Serenitatis to the west. The distinctive dark mantling of the low-lying ground around Clerke which also covers the floor of the Taurus-Littrow valley is well shown. The area is also being photographed by the Panoramic Camera and is seen in two images kindly scanned and donated by journal contributor Robin Wheeler. In frame AS15-9557P, Littrow crater is seen in the top third. Just above the centre of the image is the distinctive dark-floored valley that will become the Apollo 17 landing site. At the bottom of the image, the eastern rim of crater Beketov is just visible. The 8.4-km Beketov is better seen in frame AS15-9554P along with Jansen C. In the centre, occupying an adjacent dark-floored valley to the Apollo 17 site is the crater Ching-te, 3.7 km in diameter. The western rim of Littrow is visible near the top of this image.]

141:48:26 Worden: Okay. Go ahead.

141:48:29 Henize: Righto. Here we go. On X-ray Spectrometer, words by Izzy Adler, say the general health of the X-ray experiment is excellent.

[Isidore Adler is the Principal Investigator for the X-ray Fluorescence Spectrometer experiment.]

[One of the interesting parameters which can be determined from the X-ray data is the ratio of Aluminium to Silicon in the surface below. These are both major constituents of moonrocks and the results from the X-ray experiment will be important in understanding the large-scale make up of the Moon.]

[The ten minute period for having the Gain Step Shield off are up and the Flight Plan also calls for battery A to be charged.]

[The CM batteries are brought online during periods of heavy electrical demand. They are subsequently and regularly recharged from the spare capacity of the fuel cells when the spacecraft's needs are light.]

141:50:14 Henize: Okay. One more comment on the Gamma-ray Spectrometer, It says that regional differences have been observed in the quick look data. But details will require computer analysis for confirmation. So they're beginning to see some point-to-point differences there also.

[The investigators for the Gamma-ray Spectrometer are beginning to see reproducibility of the count-rate from this instrument.]

[Even the Preliminary Science Report, produced in the year following Apollo 15, is vague about the results from the Alpha Particle Spectrometer.]

[The Mass Spectrometer has an inlet on one side of the unit. When this faces the direction of travel (minus-X data collection period), any molecules native to the rarefied lunar atmosphere are rammed into the instrument along with molecules emitted by the spacecraft. The plus-X data collection period has the inlet being shielded by the instrument itself and the detector should only detect molecules from the spacecraft. This simple technique should discriminate between the lunar atmosphere, if it exists at 110 km height, and contamination from the CSM.]

141:54:47 Worden: Roger, Karl. We can check that out, and - if we don't see anything there, we can check it out during the EVA.

141:54:56 Henize: Very good. Good idea. On the...

141:55:01 Worden: And, the Mass Spectrometer is now fully retracted. Talkback is gray.

141:55:08 Henize: Wonderful. Just recycling it a couple of times, and it finally came in; is that what happened?

141:55:16 Worden: Well, it took - I guess probably a half a dozen re - just recycles, jogging it out, then pulling it back in again and that may be - that may be the problem. Maybe that cable is kinking some way or other.

141:55:30 Henize: Okay. Real glad to hear you got that gray talkback.

[Subsequent analysis shows that Al's diagnosis of the boom retraction problem is correct, compounded by extreme low temperatures.]

[Readers should read the Apollo 15 Lunar Surface Journal at 138:04:15 for more details of the LM water leak. This is second time the crew of this mission have had to deal with leakages from their spacecrafts' water systems.]

141:56:45 Henize: Okay, Al. We have about 10 seconds before we give an Image Motion Increase for the Mapping Camera.

[Long comm break.]

[CSM Flight Plan page 3-205.]

142:01:09 Worden: Roger, Karl. Right with you.

[Comm break.]

142:03:34 Worden: Roger... [PAO transcript adds "Got it in sight."] [Long pause.]

[Photo target 25 is the Caucasus Mountains which extend between Mare Serenitatis and Mare Imbrium north of the point where the two meet. The peaks of this range rise 6 km above the surrounding maria. Endeavour's ground track passes well south of them so four images taken by Al, AS15-96-13003 to 13006, are very oblique views of the very southern promontory. AS15-96-13004 is a good example.]

142:04:12 Worden: Roger. Power Off.

[Long comm break.]

[By the Flight Plan, Al should be beginning his meal break, though instead, he is working on the photography he had agreed to do at Mission Control's request at 140:36:09. The next three images he takes look a little south of the Caucasus at the land forms on the other side of the strait between the two maria, at the end of the Apennines. AS15-96-13008 shows one of the rilles near the Fresnel Promontory, AS15-96-13009 is of the Autolycus Gamma Prominence, an isolated outcrop of hills between Autolycus and the Apennine shore of Mare Imbrium.]

[Next, Al takes two excellent images of the Hadley landing site, AS15-96-13010 and 13011, before moving on to a sequence of five images, AS15-96-13012 to 12016, across the 39-km crater Autolycus. This is the smallest of the triangle of craters well known to even the most casual of moon watchers by being sited in Mare Imbrium in a position which has good lighting just when many evening observers are having a look at a first quarter Moon. Autolycus, with its heavily slumped walls and little rim crater, is on the small side of the threshold where an impact generates a central peak. Aristillus, on the other hand, is on the other side of that threshold. 50 km to the north and 55 km in diameter, it displays a well developed triple central peak.]

142:10:00 Worden: Okay, it's stowed. Go ahead.

142:10:03 Henize: Okay, Al - we're finding out that the - tight dead band in P20 is using a little more RCS propellant than we'd anticipated. Nothing's critical yet, but we would like to take - some preventive measures here. And we suggest that you go into the DAP - and load in a CSM weight of 30000, thirty thousand. And before you erase the current LM weight recorded [corrects himself] the current CSM weight, record it for future use. We think that'll cut down the thruster firing a bit.

142:10:46 Worden: Okay, understand. Roger. You want me to go back and reload the DAP with a CSM weight of 30 000 and record the current weight that's in there for future use.

142:10:58 Henize: That's correct.

[Long comm break.]

[In its current setup, the Stabilization and Control System (SCS), via the Digital Auto Pilot (DAP) routines, is trying to maintain Endeavour's attitude within narrow limits (the "deadband"). The current deadband value of ±0.5° was set into Noun 79 during the last far-side pass. It doesn't take long for the spacecraft to drift to these limits causing the RCS thrusters to fire appropriately to restore the attitude within the deadband. The thrusters should not fire for so long that they cause the spacecraft to move into and through to the other side of the deadband too quickly, where more thruster firing would be needed. The DAP calculates firing durations based on the spacecraft's mass. By loading a lower-than-real figure into Noun 47, the controllers are hoping that they can fool the DAP into thinking that it has a lighter CSM to rotate than is really the case and therefore cause the thrusters to fire for a shorter period.]

[Scott, from the 1971 Technical Debrief - "[To Worden] In the orbital operations, you never got close to the red line [quantities], did you?"]

[Dave is referring to a line on a hypothetical graph of RCS usage against time. They must not go beyond the red line or they jeopardise the mission.]

[Worden, from the 1971 Technical Debrief - "The last number I recall hearing was 15 percent above the red line on one quad. There was some concern about the second day of lunar orbit operation [actually the third] that we were expending fuel more rapidly than we should have been. They called up a weight change for the CSM to try and take the DAP into firing fewer times, to conserve some of that fuel. That didn't work. So we went back to the actual weight and nothing else was said. We never compromised any of the operation and we ended up not even close to the red line. I never did hear a number after the 15 percent, but I assume that we were comfortably above it."]

142:16:28 Worden: Roger, Houston. Understand that, and - one point from here, Karl, - I'm over the spot in Imbrium, I think, close to where you and Whitaker drew from, or figured out, some lava flows coming out of where the wrinkle ridge is, and at this low Sun angle, I can very clearly see some lava flows coming out of what appears to be a ridge, extending in both directions from the ridge. And I wasn't set up this time to take a picture of it, but it might be interesting on the next pass if we could get a - if we could get a PAD to take a picture of that.

[In the 1950s, Ewen Whitaker helped begin work on a series of high quality atlases of the Moon based on telescopic imagery. A self taught Englishman, he continued to study lunar imagery throughout Lunar Orbiter and Apollo periods, having an important influence on Apollo site selection and lunar science. He is credited with tracking down the exact position of the Surveyor 3 unmanned lander on Lunar Orbiter photographs by comparing landmarks on the lander's own photographs with those from Lunar Orbiter 3, thereby giving Apollo 12 a target to aim for. In retirement, he wrote (and to some extent illustrated) a lovely book that reflects his deep interest in lunar mapping, Mapping and Naming the Moon: A History of Lunar Cartography and Nomenclature.]

[As Endeavour enters lunar night, Al is due to deploy the Gamma-ray boom about now, retracting it again just prior to reaching sunlight again.]

142:17:19 Worden: I'm looking out window 3.

[Window 3 is the central of the Command Module's 5 windows and is mounted in the spacecraft's main hatch.]

[With the spacecraft travelling "sharp-end-forward", and the SIM bay facing the surface, window 3 must be looking towards the North.]

142:17:27 Worden: Just slightly north of groundtrack.

142:17:31 Henize: Very good.

142:17:32 Worden: That's right. Just down in the south, just a little.

142:17:34 Henize: Thank you. Sounds like an interesting observation, and I'm sure the guys down below will be sending you up more work to do as a result. Be careful there, now.

[Long comm break.]

[At 145:45:52, Houston will pass up instructions to photograph these lava flows at 148:00.]

[The wrinkle ridge Al is referring to is now known as Dorsum Zirkel which runs northwest from the crater Lambert to Dorsum Heim. Ferdinand Zirkel, 1838-1912 was a German geologist and Albert Heim, 1849-1937 was a Swiss geophysicist.]

[Worden, from the 1971 Visual Observation Debrief - "On the western edge of Imbrium and in [Oceanus] Procellarum, you can see the flow fronts by the difference in color."]

[Farouk El-Baz, from the 1971 Visual Observation Debrief - "Before you see the flow scarp?"]

[Worden, from the 1971 Visual Observation Debrief - "Yes, because the color is distinct and different from the flow that was underneath it. ... After you look at one area and you see 10 or 15 flows that are all overlapping and joining in that area, the picture gets a little bit confused. But that's why I say that I get the impression that there are just hundreds of flows that filled up the basin. They all look like, for example, you'd take a pail of water and sluice it out into a skating rink and let it freeze in place; then, if you do that 15 times around the same area, you would get this overlapping mixed up ice."]

[El-Baz, from the 1971 Visual Observation Debrief - "You're talking about Procellarum?"]

[Worden, from the 1971 Visual Observation Debrief - "Yes. [In Imbrium] there were a lot more than two flows. In fact, I don't recall seeing any place where it looked like there was just one big flow. All the flows were very thin and appeared as if they came out and froze in place."]

142:25:48 Worden: That's just about right, Karl. Coming right over the middle of it.

142:25:52 Henize: That must be a beautiful sight. Hey, I was sort of fascinated by the fact that, on your first couple of revs, you noted that you could really see the peaks sticking up - the central peak before you could see the rim. Is that really true?

[CapCom Karl Henize is referring to the third orbit when Apollo 15 emerged from behind the Moon. This was immediately after the burn which lowered their pericynthion to only 17 km. At 083:16:41, Dave Scott enthused about how their falling altitude and the Moon's curvature made Tsiolkovsky's central peak appear before the rim.]

Real Video file (357K)

[Part of Al's description is included in the above Real Video file, taken from NASA's post-mission documentary.]

[Worden, from the 1971 Visual Observation Debrief - "Tsiolkovsky is different. You've got a good feeling for the depth there, probably not as great as the laser shows it to be, but that's just optical. That big scarp over on the west side gives it depth. But that's just because you look at one scarp. If Tsiolkovsky did not have the central peak and if it didn't have that big scarp on the other rim, you might be fooled with the depth. It's kind of the total picture that you see. That central peak is a monster."]

[El-Baz, from the 1971 Visual Observation Debrief - "It really did look huge, and you saw the central peak before you saw the rim?"]

[Worden, from the 1971 Visual Observation Debrief - "Oh, yes. You look over the horizon, and you don't see the [near] rim until you see the central peak. Then, once you see the central peak, you realize that there's a rim there. In other words, you realize that the central peak is sitting off by itself. I guess you're up over the rim enough so that you can see down into the central peak. But the surrounding terrain looks so much alike that you don't have a feeling for the fact that there is a rim there. But that central peak sure does show up."]

142:27:11 Henize: Hey, that would be great to get pictures of that. I don't know when you were scheduled to look at that - that landslide on the northwest corner of it, but are you seeing anything of that area?

[Al will take 6 photographs of Tsiolkovsky with the 250-mm telephoto lens during his next far-side pass, perhaps prompted by this conversation. AS15-96-13017 to 13019 are three spectacular images of the central peak which can be composited to show the entire structure. 13020 and 13021 show examples of the landslides around Tsiolkovsky's rim. One other shot, AS15-96-13022 shows the "sculpture" beyond the south rim where the flying ejecta from the impact event carved furrows in the surface.]

[Al's point about the density of craters on the rock slide compared to the surrounding terrain is important because it is assumed that a greater numbers of craters on a terrain indicates older age. Planetary scientists believe that although there are short term variations in the numbers and sizes of meteoroid impacts, over very long time scales the flux has been essentially constant for the past three billion years.]

142:28:33 Worden: Just want to add one other comment to that. So far, I haven't been able to locate the other one.

142:28:43 Henize: Say again on that, Al?

142:28:49 Worden: So far, I haven't been able to locate Al-Biruni.

142:28:53 Henize: Roger. Okay. [Long pause.]

142:29:43 Henize: Al, Alvin heard that, and he feels crushed.

142:29:52 Worden: Well, tell him not to worry. I'm sure it's there and I'll - I've just got to get a little bit further south around the edge of the crater.

142:29:59 Henize: Okay. Hey, when you can get the Flight Plan and a pencil, I've got a - a few more updates to finish up on this rev.

142:30:16 Worden: Okay, go ahead.

142:30:18 Henize: Okey-doke, let's go over to 143 hours. And, at 143:09, we want to add...

142:30:27 Worden: Say, Houston, Endeavour. Go ahead with your up-dates, Karl.

142:30:30 Henize: Roger. At 143:09, we would like to add "Laser Altimeter, Off"; at 143:12, in that P20 there, we would like you to do a "Verb 25" instead of a "Verb 24"; and we would like to add, in addition to your two angles there, we would like to add "Omicron plus 161.00." Did that come through?

142:31:08 Worden: Roger. Understand, we're going to do - Omicron - add omicron to that - load of plus 161.00.

[The time given to switch off the Laser Altimeter, 143:12, coincides with the time the spacecraft is due to be maneuvered into an attitude for taking backward looking oblique photographs with the Mapping Camera. This sequence of images are AS15-1309M to 1428M. In this attitude, the science instruments in the SIM bay will not be pointing straight down and the data from the Laser Altimeter will be less useful. By switching it off, they hope to save the ailing instrument for later.]

142:31:42 Worden: Understand. At 144:26, you want to add a "Verb 25, Noun 78" - "Omicron plus 180.00."

[This double change of omicron values may be due to the error discovered at 126:46:10 when the omicron value for a P20 maneuver was found to give an incorrect attitude. Mission Control have checked the Flight Plan to ensure that nowhere else is there a wrongly defined P20.]

142:32:14 Worden: Roger. Delete "Laser Altimeter, Off."

142:32:19 Henize: And then, if we go over to 151 hours. At 151 hours and 10 minutes, we would like to change the Pan Camera operation there, and we would like to say "Stereo Exposure, Normal." And at 151:15, we would like to delete the "Pan Camera Exposure, Normal."

142:32:59 Worden: Okay, I understand. At 151:10 you want that to read "Stereo Exposure, Normal;" and at 151:15, delete that line.

142:33:08 Henize: That's correct, and that's the end of the update.

142:33:14 Worden: Okay.

[Comm break.]

142:35:47 Worden: Okay, Karl. Understand you want me to go back to normal DAP load and normal weight.

[Twenty five minutes ago, Mission Control asked Al to change the computer's knowledge of the mass of the spacecraft. This was to try and reduce the thruster firings made by the DAP in its attempt to keep the desired attitude. The strategy is not improving matters as they hoped. Note that this is not resulting in a heavy usage in propellant. However, it is in the nature of the entire system to try and wring every last ounce of performance from critical systems such as the RCS in case an emergency demands all the reserves available to get the crew out of a situation. This mentality was nicely observed in the movie film Apollo 13 when the Ken Mattingly character asks to repeat a docking simulation. Though the crew are under pressure to move on, he feels he can do it with a little less fuel.]

142:36:05 Worden: Negative. It's out.

142:36:07 Henize: Very good. Thank you.

142:36:12 Henize: Did you record an extension time on that?

142:36:19 Worden: No. I didn't get that, Karl.

142:36:21 Henize: That's okay.

[Long comm break.]

142:45:16 Worden: Okay, Karl. See you on the other side.

[Very long comm break.]

[Endeavour has disappeared from radio contact with Earth towards the end of its 33rd revolution. Rev. 34 will begin at about 143:06. Currently, all SIM bay instruments are operating except the Mass Spectrometer and, interestingly, the Mapping Camera is also operating right across lunar night. At first, this appears pointless without light to make a photograph. However, the Mapping Camera consists of two cameras, the Metric and the Stellar Cameras, exposing onto a single roll of film. These are operated in conjunction with the Laser Altimeter, the readings from which are also imprinted on this camera's film and which are required to provide contextual information for the other instruments, even over darkened lunar territory. As part of taking a measurement of height, the precise attitude of the spacecraft must be found so that if the laser pulse does not strike the surface exactly vertical, analysts can compensate. The Stellar Camera's images of stars taken at the same time as the laser pulse calibrates the laser's direction.]

[CSM Flight Plan page 3-207.]

[Al is still within his meal period which is due to end at 143:01. Just before Endeavour reaches sunlight again, Al retracts the Gamma-ray boom. He then uses P20, option 5, to make the SIM bay look back 25° from the vertical for a series of backward oblique photographs the Mapping Camera will take throughout the coming daylight pass.]

[Tsiolkovsky, with its dark, mare-like interior and spectacular central peak, is the target for visual observation by Al; specifically its northwest rim. Compared to when they first encountered this striking 198-km crater, its shadows have lengthened considerably and much more texture can be discerned. As well noting how the crater looks for his description, Al takes the six photographs using the telephoto lens.]

[These visual observations have been the subject of considerable training from Farouk El-Baz on the art of geologic description and the correct use of terminology to impart maximum information to geologists on Earth. One of the main justifications for this effort is the understanding that the well-trained human eye can discern far more subtlety than the best photograph. 27 years after the event, the lovingly crafted TV mini-series From the Earth to the Moon, made by actor Tom Hanks for HBO, set aside some time to convey the dedication which went into transforming a bunch of test pilots into very competent geologists with one episode given over to the tale of Apollo 15, its preparation and success in wresting quality science from the Moon. Although a substantial team from NASA and the USGS (U.S. Geological Survey) were involved in 15's geology training, the episode titled Mr Galileo Was Right focused on the role of Professor Lee Silver in turning Dave Scott and Jim Irwin into expert field geologists. It also showed how El-Baz went about his task of making Al Worden into a highly competent aerial observer of the Moon's landforms. While Lee Silver led Dave and Jim on foot through geologically fascinating sites, where they practised the skills they would need for EVA, Al and Farouk took to aircraft and flew over landscapes which it was felt would provide relevant experience and knowledge for his sojourn around the Moon.]

143:31:54 Worden: Hello, Houston. Endeavour reads you loud and clear.

143:31:58 Henize: Reading you loud and clear likewise.

143:32:42 Henize: Al, if you have time to listen, I have some news bulletins down here; and, somewhere in the middle, I will break in for the High Gain Antenna, Auto.

143:32:46 Worden: Okay, Karl. Go ahead.

143:32:48 Henize: Right. This is the morning national and world news - the world being, of course, the planet Earth. President Nixon, yesterday, declared his administration is determined to revitalize the American country...

143:33:13 Worden: [Garbled]

143:33:15 Henize: Go ahead. I missed that one; Al, say again.

143:33:20 Worden: That's your world right now.

143:33:23 Henize: That's right; that's our world.

143:33:26 Worden: Our world's up here right now, Karl.

143:33:29 Henize: [Laughter] I - I'll give you some news bulletins on that at the end. Things are coming along good in the EVA. Okay. President Nixon was what - he was at ceremonies dedicating a dam in Iowa, and he said the economic potential of rural areas must be developed, quote, "so that the people who live there can be first-class citizens enjoying a first-class way of life." Unquote. In the labor area, about 4,000 Houston area steel workers are expected to be off the job today in a nationwide strike against nine major steel companies. That's beginning to loom as a pretty big factor in [the] economic world down here. Senator Mansfield said Saturday chances are good that the senate will reach an agreement to stop talking and speed up a vote on a bill to rescue Lockheed Aircraft Corporation. The President of Pakistan has accused neighboring India of continued artillery strikes across the border and said, quote, "We are very near to war with India;" a very sad note there. And Senator Edward Kennedy and Senator Edmond Muskie are tied for the top spot in the latest Democratic standings according to the Gallup Poll. I'm sure you'll be fascinated. And in the world of sports, in football, the Houston Oilers lost their first exhibition game to Los Angeles, 17 to 6. In baseball, the Astros won for a change, and beat the Expos 6 to 4; and in golf, Jack Nicklaus and Arnie Palmer shot a total of 64 to take a 4 stroke lead in the PGA National Team Championship in Ligonier, Pennsylvania. Okay, and we are ready for High Gain [Antenna, HGA], Auto, Al.

[Once the HGA has reacquired the Earth after AOS (Acquisition Of Signal), it is always switched to Auto. This may be to inhibit the antenna from returning to the preset position settings in case of a temporary break in the link with Earth.]

143:36:12 Worden: Sounds great.

143:36:14 Henize: Yep. Everything's going great, both in orbit and on the surface. Everybody is very pleased.

143:36:31 Worden: Okay, Karl. If you're through with the news, let me give you some words on Tsiolkovsky.

143:36:37 Henize: Great, we're listening.

143:36:46 Worden: Okay, I'll take the items one at a time as they come. First off, the central peak. The central peak is - is a very large - spur peak on the - on the south and east sides, getting blocky on the north side; and there's what appears to be some layering visible on the - on the south and west exposed scarp of the peak, dipping to the north about 30 degrees.

[Worden, from the 1971 Visual Observation Debrief - "There appeared to be, from my vantage point, distinct layering that was fairly uniform and horizontal. In other words, the layers weren't rotated with respect to the shape of the peak. It appeared as if the feature had been raised up and the layering remained horizontal."]

143:37:30 Worden: The - Okay. The light material - the light colored flow material - around the edges of the - of the basin - texture appear to be nothing more than just simple mass wasting off of the edges - or off the - of the rims around the basin. The rims themselves are quite - cut with the mass wasting in a - oh, I'd say an extent of about 330 degrees on the north, east, and south sides. Now, on the west side, the rim there is a very, very, large, clean scarp; and when I say clean, it goes almost from the basin floor to the - to the rim itself in one large chunk. And that scarp appears to define the limits of a couple of fault zones that go through that rim of Tsiolkovsky. It was kind - it - I couldn't trace the fault zone beyond Tsiolkovsky from the vantage point I had very well, but they're very distinct in the wall itself. And one fault zone coincides, or - occurs in the same location as the southernmost edge of what appears to be a rock glacier extending northwest into Fermi. Now, that rock glacier has all the flow bending and the loping toes characteristic of what we consider a rock slide; however, one - one feature about that slide that I mentioned before is that it has what looks like fairly fresh crater impacts on the slide itself and seems to have more impacts - in other words, a higher density of craters than the - than the - surrounding floor of Fermi, although Fermi looks - the floor looks much older - its much smoother, more like a Cayley formation.

[One of the often reproduced frames from the metric section of the Mapping Camera, AS15-0757M, is a stunning oblique view over Tsiolkovsky looking towards the west. The extent of the mass wasting from the rim onto the interior of the crater is evident including its absence from a small portion of the west rim, the clean scarp which Al speaks about. During revolution 15, Al took AS15-97-13161 which is a beautiful view of this scarp, and AS15-96-13021 shows a rock avalanche down the crater wall just south of the clean scarp.]

[Tsiolkovsky slightly overlaps the older and much more degraded 210-km crater, Fermi, on its western edge. Enrico Fermi, 1901-1954, was an Italian born nuclear physicist. Al is comparing the ancient floor of Fermi to the Cayley formation, a distinctive plains area which is smooth and light coloured and which lies southeast of Mare Imbrium. It was believed to be volcanic in origin but later interpretations view it is being a huge deposit of ejecta from the impact which created the Imbrium basin.]

143:40:01 Worden: Looking - Okay. Looking more to the south, I see no evidence of another rock slide to the south. The pictures might indicate - might hint at some kind of a rock slide there, but it appears that it's - that its more ejecta now. The picture [in the landmark book] doesn't clearly show the ejecta from Tsiolkovsky, but the ejecta pattern and the flow - the flow lines are - at least observable around most of Tsiolkovsky, and the ones that we see on the south and west side of Tsiolkovsky seem to be more ejecta than anything else. I couldn't see any distinct unit there that could have been a flow, such as the one in the northwest corner. And it - it appears that what lineaments there are in that particular part of the - of the ejecta are merely e - ejecta patterns.

[AS15-96-13022 displays these lineaments clearly.]

143:42:37 Henize: Roger, Al. [Long pause.]

[Waterman is a 70-km eroded crater on the southern side of Tsiolkovsky.]

[At 107:55, Al took 6 frames, AS15-94-12745 to 12751, of this pair of craters which show the slumping of the wall between them.]

143:47:23 Worden: Okay, now, we go on to Picard.

[Comm break.]

[Picard is scheduled to be Al's next target for visual observation and is the most prominent of the craters within Mare Crisium at 23 km diameter. He will photograph it after three more orbits and these two shots are AS15-94-12832 and 12833. Note that the Sun is nearly overhead Mare Crisium and Al will therefore discuss colour and albedo differences as the lack of shadow deprives him of much of a sense of depth.]

143:49:20 Henize: Endeavour, go ahead.

143:49:24 Worden: Okay, Houston. Endeavour's coming up over Picard, and I thought I'd just go ahead and talk while we're going over Picard. First, talking about the color variations, Picard is a slightly different color than the rest of (the) mare basin. It's - I guess what I would consider Crisium - a light brownish gray. Picard, itself, is - is - is more of a brown tone, and it has a darker halo around it. I can see some of the brown - material just on the outside of the rim; and outside of that is some darker material that gradually turns into the gray of Mare Crisium. Inside Picard, I can see - well, let's see now, let's count them - 1, 2, 3, 4, 5, 6, six distinct rings that go around the inside of Picard. And the - and the walls in Picard are very shallow. It looks like a very shallow, almost like a - a dish - kind of basin, and gently from the edges on in toward the center, and, as I say, I can count - five or six rings inside, that are all concentric with the center of the basin. And I can see some definite layering in - in the - particularly in the upper boundary of the rim.

[Al's description of Picard appends his earlier comm at 128:07:19.]

[El-Baz, from the 1971 Visual Observation Debrief - "Was there anything specific about the color of Picard?"]

[Worden, from the 1971 Visual Observation Debrief - "Yes, there was. The mare surface itself is darker - I have to subtract mentally the ejecta from Proclus. The mare surface itself is almost a gunpowder color. ... It's almost black, but then you get fooled because you've got this very light ejecta - very thin ejecta - that is laid down over the mare surface, so that when you're looking at it from some distance away, it doesn't look nearly as black. A lot of that white comes through. The best way I can describe Picard is alternating layers of cream and brown."]

[El-Baz, from the 1971 Visual Observation Debrief - "So it was quite different then?"]

[Worden, from the 1971 Visual Observation Debrief - "Quite different from the surface, yes."]

[El-Baz, from the 1971 Visual Observation Debrief - "And that goes for the whole crater or the interior only?"]

[Worden, from the 1971 Visual Observation Debrief - "The interior is about the only thing you see of the crater. Once you get to the rim, that part from there on out looks pretty much like the rest of the surface. The interior was so distinctively different that that was the thing we looked at. Our eyes just kind of went to the interior, because it was so different. It was kind of a dark brown- and cream-colored alternating layers on the sides of Picard and Peirce. In fact, the interior of a lot of the craters we saw had distinct layering. They had a brown color and not the black color that you see on the surface. ... In the craters in the upland material, there was an absence of layering that I could see, but in almost all the mare-type craters - or the mare-located craters - there was that kind of layering."]

[Al also discusses the appearance of the rays from Proclus over Mare Crisium.]

[Worden, from the 1971 Visual Observation Debrief - "It's very strange the way the ejecta from, particularly, Proclus crosses Crisium. It's almost like flying above a haze layer and looking down through the haze layer at the surface. I don't know whether you've ever had the opportunity to do that or not, but that ejecta from that crater doesn't look like it's resting on the top of Crisium. It looks like it's suspended over it. It gives a very filmy, very gauzy appearance to the whole thing."]

[El-Baz, from the 1971 Visual Observation Debrief - "It must be very thin."]

[Worden, from the 1971 Visual Observation Debrief - "Yes. And I guess the reason it looks like it's just draped or suspended over it is that almost any way you look at it, if it goes through a crater or it goes through a ripple ridge or it goes through any topographic feature, it doesn't make any difference from what angle you view it; those lines - the ejecta pattern - are straight."]

[El-Baz, from the 1971 Visual Observation Debrief - "Okay; now when the ray goes through a topographic prominence or a negative depression of some sort, do you still see the ray through that?"]

[Worden, from the 1971 Visual Observation Debrief - "Yes."]

[El-Baz, from the 1971 Visual Observation Debrief - "Through the crater on top of the ridge?"]

[Worden, from the 1971 Visual Observation Debrief - "As a matter of fact, the areas where you don't see the ray seem to be independent of topographic features. There would be some areas where you wouldn't see any rays from Proclus. I guess the reason for that is that they might have been covered up by material from another crater that was a different color. So, you get rather vague, obscure patterns on the ground where the ray patterns cross, and you don't see the ray from Proclus. But it didn't seem to be tied into topographic features. It seemed to be more a function of just overlapping rays or ray patterns built on top of each other. But that's about all you can see in Crisium. It's like looking at a star field and trying to pick out some familiar stars. At first, all you see are stars; then, you have to orient yourself by picking out a star that you know; and then you pick out the other stars around it. This is almost the same thing. When you first look at Crisium, all you see is the ray pattern. You don't see any features at all; you just see the ray pattern. And then you start picking out some craters or some features that you know. From there, of course, you can see through the ray pattern and it doesn't distract you anymore. Then, you can pick up all these other things. That ray pattern is really prominent. And of course, it looked to me like 90 percent, of it was from Proclus. That's really a ray pattern that just covered everything."]

[El-Baz, from the 1971 Visual Observation Debrief - "Some of the ridges are over 100 meters high, so the ray material cannot be traveling close to the surface. Remember our discussion of how high the ray material would fly and the theory of it cutting right across the surface? If it did, it could not possibly cover the ridge and go right through it. Oh, yes. If it does, it's got to be sticking close to the ground the whole way, and that's just not the case, Yes, it's a very continuous ray pattern, as far as the topography is concerned."]

[There is further discussion of Picard at 149:57:24 including further debriefing with Farouk El-Baz.]

143:52:09 Henize: Roger; we're - we're copying loud and clear.

[Unlike the prominent, fresh nature of Picard, Lick is a flooded crater named after the philanthropist James Lick, 1796-1876, who financed the Lick Observatory in California. Lick is flooded in the sense that the lava material which filled Mare Crisium 3.3 billion years ago, also filled the 31-km crater that was the fresh basin of Lick, sited at the edge of the Crisium basin. After the lava's stopped filling Crisium, Picard was blasted into the smooth mare surface to the north and east of Lick. The dating of mare lavas returned by Apollo, and in the case of Mare Crisium, by the returned samples from Luna 24, allow the relative dating of many features associated with the mare. In this case, we can see that Picard is younger than 3.3 billion years while Lick is older. Also, Lick must have been formed between the impact which formed the Crisium basin and the period when the lavas filled that basin. Although we do not have a date for the Crisium impact, we can see that the dates for the creation of Lick and Picard have been constrained.]

[Yerkes is another lava flooded crater, 36 km diameter, on the margins of Crisium and like Lick, is named after a benefactor of a great observatory. In 1897, Charles Yerkes, 1837-1905, financed the construction of what is still the largest refracting telescope in the world at 1.01 metres. This extraordinary instrument is still in regular use over one hundred years after it was built.]

[Although not scheduled to do so, Al is taking an additional opportunity to view the spectacular crater, Proclus, and its distinctive asymmetrical ray pattern. His first extensive description of the crater was at 128:07:19.]

143:54:49 Henize: Roger, Al; we copy.

143:54:54 Worden: Hope you could understand all that, Karl. I had to talk fast and formulate as I went.

143:55:00 Henize: Roger, it came through loud and clear, and I think it was quite understandable. Very good.

143:55:15 Worden: Okay; I'm drawing a couple of little pictures of it to show you when I get back.

[The following three images from the Mapping Camera are a sequence from the current backward-looking sequence as they pass over the future Apollo 17 landing site.

This image, AS15-1399M, shows the Sinus Amoris region just east of the Taurus-Littrow valley. The craters marked 'D' and 'E' are large, flooded craters which, especially in the case of 'D', are almost completely inundated by the basalt of Mare Tranquillitatis.

Image AS15-1403M is similar to many shown in this journal as it concentrates on the Taurus-Littrow valley where Apollo 17 will land.

The transition between the light and dark surface of Mare Serenitatis is very clear. Skipping another frame, we move on to image AS15-1405M and further out across Mare Serenitatis.

Again, note the contrast between the Taurus-Littrow region and the bulk of Mare Serenitatis. Also, there is a fainter transition on a larger scale that runs around the edge of the mare which can be running down the image between Borel and Clerke and northwest of Rimae Plinius.]

143:55:35 Worden: Okay. Okay, Karl. Stand by one.

[Comm break.]

[By the Flight Plan, the Earthshine photography is to consist of 20 frames through window 3, the central hatch window of the Command Module, using very high speed black & white film in the 35-mm Nikon camera. The Nikon will have its 55-mm lens open at f/1.2 and at the beginning of the procedure, the camera is set to a shutter speed of 1/500th of a second. The time that Henize is about to be give is not the time that the photography begins, it is the time that Al will reset and restart the mission timer. The timer will then be used to sequence events during photography, as follows: As soon as he has reset the timer, Al will cover the lens, take one blank frame, wind on and then set the shutter speed to 1/125. At 4 minutes on the timer, he will take 4 frames at 30 second intervals and then change the shutter to 1/15. When the timer reaches 6 minutes, he takes another 4 frames at 30 second intervals and sets the shutter to 1/8th of a second. These 8 frames are taken as Endeavour crosses the terminator but while the spacecraft itself is still in sunlight. Beginning at 8 minutes on the timer, Al takes 10 frames, again at 30 second intervals while Endeavour passes into near darkness, where the Moon below is lit only by the reflecting Earth.]

[Observers on Earth can see the same effect, often, though erroneously called the 'Ashen Light', when the Moon is nearly new. While the Sun illuminates only a thin crescent, a nearly full Earth illuminates the dark hemisphere of the Moon which becomes quite discernible with the naked eye. Some cutely describe this effect as the Old Moon in the arms of the New. More accurately, the Ashen Light refers to a similar effect seen on the planet Venus by some Earthbound observers though, in this case, it is uncertain what mechanism is responsible.]

143:57:13 Henize: Roger. Earthshine PAD at about 144 hours and 5 minutes in your Flight Plan; the number is 144:10:32.

143:57:29 Worden: Understand 144:10:32.

143:57:32 Henize: Roger; and on the next page, a Map Camera photo PAD; take it?

143:57:40 Worden: Go.

143:57:41 Henize: Start, 145:14:16; stop, 146:13:56. [Long pause.]

143:58:19 Henize: The - did the Map Camera photo PAD...

143:58:21 Worden: Okay, I have my Mapping Camera photo PAD.

143:58:23 Henize: Roger.

143:58:26 Worden: Negative; you - you were cut out.

143:58:28 Henize: Oh, Roger. Mapping Camera photo PAD. Start, 145:14:16; stop, 146:13:56.

143:58:42 Worden: Understand. T-start, 145:14:16; T-stop, 146:13:56.

143:58:52 Henize: That's correct.

[Very long comm break.]

[CSM Flight Plan page 3-209.]

[The current run of the Mapping Camera, taking backward looking oblique shots of the lunar surface, is about to come to an end. The next run, which CapCom Karl Henize has just read up to Al, will also take oblique photographs, this time with the spacecraft rotated to make the Mapping Camera look north 40° from the vertical. This sequence runs from AS15-1430M to 1559M.]

144:09:19 Worden: Roger, Karl.

[Long comm break.]

144:14:29 Worden: Roger, Karl; understand. And, listen, since I got all the lights turned out here, how about stepping me through the Earthshine photos.

[Worden, from the 1971 Technical Debrief - "I did find that I got into a mode of operation where the ground would give me 30-second warnings on something which was in the Flight Plan. That meant I knew the sequence of things coming in the Flight Plan, but I got a reminder from the ground. If there was a 10-minute period before the next item had to be done, then I could completely forget about the sequencing in the Flight Plan. The ground would give me a 30-second warning, and that would be a cue to me to go back to the Flight Plan and do that function. I found that very useful."]

144:15:17 Worden: And, Karl, I hope these all turn out, because this is the - the area on the last rev that I commented on all the lava flows, and we're right over now taking pictures.

144:15:27 Henize: Very good. [Long pause.]

144:16:07 Henize: Okay, after your fourth frame, you're going to change the shutter to 1/15th of a second. And - and then take four more frames at 30 second intervals.

144:16:17 Worden: Okay, 1/15th. [Long pause.]

144:16:34 Henize: I'm sorry; I could have been counting time for you, too. We're coming up to plus 6 minutes, which should be about the 4th frame at the old setting. We'll mark on 6 minutes.

144:16:47 Worden: Okay, got it.

144:16:49 Henize: And I'll call out times for you now, too. We go to 1/15th of a second.

144:16:55 Worden: Okay, I just took one frame at 1/15th.

144:16:58 Henize: Excellent. [Long pause.]

144:17:22 Henize: [It is now] Plus 30 seconds after your first picture.

144:17:54 Henize: Take number 3.

144:18:24 Henize: Take number 4, and change shutter setting to 1/8th.

144:18:34 Worden: Roger; 1/8th.

144:18:41 Henize: Now we're going to take 10 frames at 30 second intervals. Give me a mark on your first one.

144:18:48 Worden: Okay.

144:18:49 Worden: Mark. [Long pause.]

144:19:23 Henize: Time for number 2.

144:19:28 Worden: On. [Long pause.]

144:19:53 Henize: Take 3. [Long pause.]

144:20:23 Henize: Take 4. [Long pause.]

144:20:52 Henize: Take number 5. [Long pause.]

144:21:22 Henize: Take number 6. [Long pause.]

144:21:52 Henize: Take 7.

144:21:57 Worden: Roger; take 7, and I just went past the spacecraft terminator.

144:22:07 Henize: Say again? Roger; we copy.

144:22:13 Worden: Okay, I just went by spacecraft terminator.

144:22:17 Henize: Roger; we copy.

[By "spacecraft terminator", Al is referring to the passage of the spacecraft into the Moon's shadow, an event which happens about 6 minutes after it crosses over the lunar terminator.]

144:22:52 Henize: Take number 9. [Long pause.]

144:23:22 Henize: Take number 10. Change the shutter to 1/500th, cover the lens, and cycle one frame.

144:23:40 Worden: Okay; thank you.

[Comm break.]

144:25:39 Worden: Roger; Karl. I'm with it.

[Comm break.]

[All through this daylight pass, the CSM has been flying nose forward and down as the Mapping Camera has been taking backward looking oblique photographs. Values given to P20 to control this attitude are to be changed to make the SIM bay point directly below the spacecraft with the Command Module's apex facing the direction of travel. The first two values define a vector leading from Endeavour at right angles to the SIM bay. P20 has already been told to point this vector towards the centre of the Moon. The third value, omicron, defines the attitude of the spacecraft around this vector with a value of 180° pointing the sharp end forward. Note that, with respect to the stars, the spacecraft rotates once every two hours to match the orbital period, a so-called "orb rate" maneuver.]

144:28:51 Worden: Roger. I'm ready now. Gamma-ray boom going out.

144:28:56 Worden: Now.

144:28:57 Henize: Thank you.

[Comm break.]

144:30:18 Worden: Yeah, I guess that's right, Karl.

[Comm break.]

[Al's exercise period is scheduled to extend from 144:30 to 145:00.]

144:31:42 Worden: Mark; on the Gamma-ray boom.

144:31:45 Henize: Thank you.

[Comm break.]

144:34:42 Worden: Tell them to be careful.

144:34:45 Henize: Roger.

[Long comm break.]

144:42:00 Worden: Roger, Karl.

144:42:03 Henize: See you on the other side.

144:42:08 Worden: Okay.

[Very long comm break.]

[Having restored the spacecraft to the plus-X forward SIM bay attitude, the instruments commence returning full quality data. Meanwhile, as Endeavour passes over the night side of the Moon, Al takes his exercise. The CSM begins revolution number 35 at about 145:01 and comes back into sunlight soon after. Al maneuvers the spacecraft into an attitude which has the SIM bay looking 40° north from the vertical for more oblique Mapping Camera photography. Once again quality of the data from the science instruments is degraded as they are not pointing directly down. The Mapping Camera will be operated throughout this daylit pass.]

[CSM Flight Plan page 3-211.]

145:29:50 Worden: Hello, Houston; Endeavour. Reading you loud and clear.

145:29:56 Henize: Same here. How goes it up there?

145:30:01 Fine, Karl. And I got a couple of comments on Tsiolkovsky, in addition to what I said last rev.

145:30:09 Henize: Go ahead, we're ready to copy.

145:30:14 Worden: Okay, talk - discussing the - the flow in crater Waterman, south of Tsiolkovsky, I guess what I said before still applies. The - what looks like on a map is the channel between Waterman and Tsiolkovsky is, in fact, too high for anything to flow between the two. There's - there's definitely some elevation there. However, looking at it this time, it's pretty plain that that channel - or gully, or whatever you call the breach in - in Tsiolkovsky's wall there between Waterman and Tsiolkovsky is caused by a graben-like fault system. There are two faults that run through there, and they run almost north and south right towards the central peaks, diverging - the one - the one on the west side, is slightly - is angled slightly to the northwest, but the other one goes almost directly north. And the source of the lava flow in Waterman appears to be high in the - in the wall of Waterman, on the north edge, right where the fault zone crosses the - the rim of Waterman.

145:31:30 Henize: Roger, Al. We copy.

145:31:35 Worden: Okay, now there are a couple of other small - small craters around Tsiolkovsky. Particularly, one on the north side, on the northeast corner, the first large crater that you see there, has a very distinctive lava flow or some kind of flow down in the crater. And that flow also originates up in the corner or up in the - in the high towards the rim of that particular crater, where there's some contact between the - the Tsiolkovsky rim and the rim of that small crater.

145:32:26 Henize: Roger.

145:32:31 Worden: Now again, I saw no evidence of - of any kind of a rock slide to the south of Tsiolkovsky, but the one on the west there is, looks - you know every time I go over it - it certainly confirms my opinion that that's a rock slide. The lineaments, the way the - the thing ended, the lobate - the lobate tongues on it and everything. It's interesting that the rim of Tsiolkovsky, on the west side there, is - different from - across that fault zone - is quite different from [what] it is around the rest of the crater, maybe suggesting that that [is] the source of the flow. The rim seems to be not as sharply defined; it's lower and appears to be out from the edge of the basin more than the rest of the - of the boundary or the rest of the ejecta pattern around Tsiolkovsky, and there, where that very steep, almost smooth scarp is, on the west of Tsiolkovsky, seems to be the - the point at which it starts.

[Al's extensive descriptions are being carefully listened to by the geologists in one of the backrooms at Mission Control, Houston. Any requirement to feedback information or queries to any of the crews, whether on the surface or in orbit, is always via the backup crew. Since Al's backup CMP is Vance Brand, it is he who fulfils this role for the orbital mission, and being an astronaut himself, he may elect to speak to Al directly rather than via the CapCom. Except for very special occasions, like when the President of the United States spoke to the Apollo 11 surface crew, or when Lee Silver, the crew's esteemed professor, is granted a conversation with Dave, Jim and Al just before Endeavour returns to Earth, only other astronauts are permitted to speak over the air/ground link.]

145:34:07 Worden: Oh, yes, Vance, very definitely. There are a couple of fault zones, through there, and you can - you can see the displacement quite clearly from the air. The one, the fault zone between Waterman and Tsiolkovsky, is a - is a lot more subtle, but I - but I'm quite sure that, that's what's going on there. But the one on the west side is - is very clear. That - that's true.

145:34:29 Brand: Al, we'd like to have High Gain, Auto.

145:34:37 Worden: And, Vance, another comment about that. You got High Gain, Auto, by the way. Another comment about that, where that fault zone appears on the west side, there's much less mass wasting into the interbasin of Tsiolkovsky, than there is around the rest of the - of the crater. Most of that mass wasting seems to taken place outside the crater.

145:35:00 Brand: That's an interesting observation.

[Comm break.]

145:36:19 Worden: Oh, great.

145:36:20 Henize: ...listening on our loop with great interest. Except when you go behind the Moon, then they - then they watch the other show that's taking place on the surface. They said to say "Hello." And, they sound like they're having a good time up there.

145:36:36 Worden: Very good. Very good. Hello, folks.

[Long comm break.]

[Throughout the early American space program, it was customary for NASA to supply close relatives of the astronauts with a small loudspeaker, or 'squawk box' to let them listen in to the air-ground communication. The movie Apollo 13 has a scene in Marilyn Lovell's home when she allows herself to break down in private while the squawk box beside her hisses with anonymous static.]

145:40:28 Worden: Roger.

[Long comm break.]

145:45:51 Worden: Okay, Karl; go ahead.

145:45:52 Henize: Okay. 148 hours and 0 minutes, they would like to have you get some good shots on those lava flows you saw over in Imbrium. And the recommendations that we have are as follows: CM3, EL, 250 mm lens, CEX, f5.6, 1/125, infinity, 5 frames at 10 second intervals. Recommend convergent photos starting at TCA minus 30 seconds. The aim point is up to you. Magazine Q, and record frame number. And then on the same page, 148 hours and 18 minutes, we don't need to do that P52 there, because the platform looks very good.

[At 142:16:28, Al had mentioned to Mission Control about seeing evidence of lava flows appearing to come from a ridge on Mare Imbrium and requested that a PAD be read up for some photography of it. This photography is to be taken out window 3, the central, hatch window, using the Hasselblad with a 250 mm lens onto colour daylight film using magazine Q. Mission Control also ask that he takes photographs of the same spot at 10 second intervals, allowing the motion of the spacecraft to change the viewpoint by about 16 km with each image. This will allow the use of stereoscopic techniques to help determine height differences across the landform in question.]

145:47:38 Henize: That's correct.

145:47:42 Worden: And, also, delete the P52.

145:47:44 Henize: Roger. [Long pause.]

145:48:01 Worden: Karl, while we're going over Crisium here. Looking down at Picard, at Peirce and at Lick, I noticed that all of those craters, that's - that's Lick Delta by the way, Lick Delta, Picard, and Peirce, all look like - they're - they're all about the same. They all have the same ring structure, all have the same low rims. The rims are - are - are what look like very shallow [elevation] compared to the rims on the other craters I've seen around. And, also, they all have a slightly darker halo effect around the - the entire crater. But the - the color difference is very subtle.

145:48:48 Henize: Roger, Al. As I look on the map here, they look like they might have been old craters flooded by the mare. Is that - does that seem feasible to you as you look at them?

[Lick Delta, a 14-km crater, is now known as Greaves, after William Greaves, 1897-1955, a former Astronomer Royal for Scotland. CapCom Karl Henize may be confused by the hearing the name 'Lick' which is a flooded crater on the margins of Mare Crisium. Picard, Peirce and Lick Delta (now Greaves) are all plainly the results of impacts which excavated the lava plains of Mare Crisium and exposed layering within the mare structure.]

145:49:11 Henize: Roger. Okay. [Long pause.]

[Soon, Al is scheduled to make some visual observations of the Littrow area. After his comments on previous orbits, Littrow is generating increasing interest among the geologists in the backroom.]

145:50:15 Speaker (in Mission Control): Sulpicius Gallus?

145:50:16 Henize: ...Sulpicius Gallus. Or do you...

145:50:18 Worden: ...yes, Okay. Sulpicius Gallus. Certainly, Karl.

145:50:21 Henize: Right. Do they - do they look like very similar areas, or are there some contrasts there?

[The roughly circular Mare Serenitatis has two major areas of dark mantling around its shore, the Littrow area in the east and the Sulpicius Gallus area to the southwest.]

145:50:35 Henize: Okay. That's for future reference then.

145:50:40 Worden: Yes, okay. But I'll - if - if I can see across Serenitatis there, I'll - I'll give you a hack on that.

145:51:05 Henize: Okay. I guess I should keep quiet a while and let you look at Littrow coming up in about a minute. [Long pause.]

145:51:55 Henize: Al, we can have Pan Camera Power, Off now.

145:52:01 Worden: Okay. Pan Camera Power, Off.

[Long comm break.]

145:57:07 Henize: Go ahead, Endeavour.

145:57:12 Worden: Okay. Karl, I can give you at least a partial answer on that question. The - the coloration that seems to be continuous from Littrow all the way around through Sulpicius Gallus is the middle color. It's slightly darker than the rest of the mare basin [means surface] itself and not quite as dark as some isolated or localized areas within the Littrow area.

[Al has come up with a rudimentary classification of the shades of grey seen in the lowland areas in and around Mare Serenitatis.

This photograph was taken by the Jupiter-bound probe, Galileo, during its gravity assist flyby of the Earth-Moon system on December 7 and 8, 1992. The spacecraft flew over the Moon's north pole and this image shows Mare Serenitatis as seen from this northerly perspective. Note how the bulk of the mare is lighter than the margins. This dark margin is what Al refers to as "the middle color." The darker, localised areas are visible to the bottom right of the picture. Another dark area around Sulpicius Gallus is visible by following the shore of Mare Serenitatis around to the ten o'clock position on this photograph.]

[Once again, Al describes the appearance of apparent cinder cones within the area of dark mantling near the crater Littrow. This observation, along with those at 079:23:46, 122:18:17 and 128:12:46, is enough to sway mission scientists and planners towards sending Apollo 17 to the valley of Taurus-Littrow in seventeen months time.]

[Al appears to be making a common error by confusing the terms 'mare' and 'basin.' To clarify, when a large body, perhaps tens of kilometres across, impacts the lunar surface, it creates an enormous depression in the Moon's figure. This depression is referred to as a basin. About 4 billion years ago, the Moon sustained a number of such impacts, a period often referred to as the Great Bombardment. Later, lava from the Moon's interior welled up through fissures in the basins to fill them. These huge areas of solidified lava, or basalt, are termed the maria and it would be correct to describe a mare as something which fills a basin. For most of the Moon's maria, the only portion of the basin we can see is the rim. An exception to this is Mare Orientale, which contains far less basalt than most of the other maria. Orientale displays many of the spectacular features of a large impact basin including the radial "sculpture" and multiple rings. In the above description by Al Worden, he is clearly making comparisons within the surface of the Serenitatis mare and not of the basin.]

[Journal contributor Robin Wheeler has kindly supplied images from his collection of Apollo SIM camera photography. Here, we include a sequence of the 33 north-facing views taken by the Mapping Camera during this pass as the spacecraft moves across Mare Serenitatis, Mare Imbrium and past the terminator. All the images are available via links but only every second one will have a guide image included.

Mapping Camera frame AS15-1524M looks north along the dark-toned eastern shore of Mare Imbrium with Posidonius in the distance. 1525M brings the small crater, Very, into the centre of the frame.

1526M has the 7.6-km crater Sarabhai in view. Note the very long, light-coloured streak that runs across the mare to its northeastern shore. 1527M has this streak nearly beneath the camera. If this streak is viewed in the context of this full Moon image, kindly donated by astrophotographer Rob Gendler, the streak appears to be part of the huge ray system emanating from Tycho, over 4,000 km to the south. Tycho's rays dominate the Moon's near side. The streak is also coincident with the crater Bessel, the largest crater well within the margin of Mare Serenitatis though it is only 16 km in diameter.]

[Rather surprisingly, there are no good photographs of Bessel in the Apollo 15 Hasselblad collection.]

[The Mapping Camera continues imaging the expanse of Mare Serenitatis.

This continues on 1529M.

On 1530M above, and 1531M the tiny yet highly visible crater Linné comes into view.]

[CSM Flight Plan page 3-213.]

[Al is due to change LiOH canister 12 for number 10 in the B receptacle. 10 will be stowed in compartment A9.]

146:00:16 Worden: And that ledge looks like it's caused by a - a harder material.

146:00:21 Henize: Roger. You're coming through loud and clear. [Long pause.]

146:00:43 Henize: Do any of the other craters around that area, around Bessel, show the same sort of interior ledge like that?

146:01:06 Worden: Well, unfortunately, Bessel is the only one of that magnitude around - around that particular area. And I don't see any other craters that appear to go down below - whose depth appears to go down below the depth of the rim in Bessel.

146:01:15 Henize: Right. I - the only two I see possible here are Bessel E and Sulpicius Gallus; and I guess they might not go that deep even so. [Long pause.]

[Bessel E is another crater which has since been renamed by the International Astronomical Union (IAU) as Bobillier after a 19th century French geometer. It is 6.5 km in diameter. The Mapping Camera looks north across the western shoreline of Mare Serenitatis.

At the lower centre of this image, the irregular depression, Krishna, is visible. In 1533M, the Montes Caucasus range come into view.

By 1534M above and 1535M, we are looking at the mountain ranges that separate the two great maria. The Caucasus range is to the top of the image, the Apennine range to the bottom.

This division is very apparent in 1536M above. The landing site in the foreground is seen in beautiful context with the maria, the mountains and the great craters, Aristillus and Autolycus. 1537M continues the pass.

This is 1538M which put the landing site in context with Palus Putredinus. Note the graben-type rilles, Rimae Fresnel, between the landing site and Autolycus. These are likely expansion features and have a very different morphology from the sinuous Rima Hadley. The large, flooded crater Archimedes starts coming into view in 1539M.

In 1540M above, the triumvirate of craters, Archimedes, Aristillus and Autolycus, that rule the eastern half of Mare Imbrium are all seen. In 1541M, the remains of the Archimedes ejecta blanket, Montes Archimedes, comes into the foreground.]

146:02:08 Worden: No, I haven't yet, Karl. Maybe this is a good time to do it.

[Very long comm break.]

[Al does not make any mention of seeing Autolycus or Aristillus during the rest of this pass. The Mapping Camera continues taking oblique images looking north of the spacecraft's position as the spacecraft moves towards lunar sunrise.

This image, AS15-1542M, is an excellent shot of Archimedes and the Apennine Bench Formation which includes Montes Archimedes. Beyond Archimedes is Montes Spitzbergen. 1543M moves the view out over Mare Imbrium.

This image, 1544M, is of the area west of Archimedes. Note the pair of craters Feuillée and Beer, and the string of craters strung out east of Beer, also well shown in 1545M. Frame 1546M takes us over the featureless expanse of the Imbrium basalt flows, peppered with the smaller craters. Many of those craters are secondary impacts from the formation of the mare's large crater. Coming into view in 1547M is one of these, Timocharis, which is more visible in 1548M

Note the strings of small craters around the main structure at one to two crater-diameters distance. These are all secondary impacts from the ejecta that was thrown out by the primary impact that formed Timocharis. Our vicarious flight across the Moon continues with 1549M, 1550M and 1551M.

The above image has the terminator approaching from the left as we look north of Lambert over the wrinkle ridges and small craters of the mare. In 1553M, a particularly dominant wrinkle ridge, Dorsum Zirkel, comes into view. Running northeast from it and slightly darker than the surrounding surface are solidified lava flows and they are part of the terrain which Al will photograph with the Hasselblad during his next pass.

This image also shows the lobate flows. On the left, Mons La Hire is coming into view. 1555M continues towards the terminator.

This is the final image in this sequence. In it, the lava flows that Al has identified is well seen in the very low-angle lighting. It runs in a long ribbon from southwest to northeast. Though the flow evidently lies on top of older flows, both are of great antiquity as evidenced by the presence of craters across both.]

146:13:07 Worden: Roger, Houston.

[Long comm break.]

[Ha