Apollo 15

This chapter covers the start of the tenth day of the mission. Date: 4 August 1971.

Although their primary mission is completed, the crew of Apollo 15 still has a long day of work ahead of them before they head home. Photography and running the SIM bay will occupy virtually all of their time for the next ten hours as they orbit the Moon in Endeavour. Following these tasks, all efforts will focus on preparations for Trans-Earth Injection (TEI) which will raise the spacecraft's velocity, slinging it out of lunar orbit and on a course towards Earth.

Currently, the crew of Dave Scott, Jim Irwin and Al Worden have just begun their 8-hour rest period on time. As they orbit the Moon, Endeavour's SIM bay is kept facing the surface by having the spacecraft slowly rotate in synchronism with their orbital period, a so-called orb-rate rotation. They are flying backwards with the SPS engine bell facing the direction of travel. This orientation aims the rearward-facing inlet of the Mass Spectrometer into any oncoming molecules of the Moon's staggeringly tenuous atmosphere. Other experiments operating just now are the Alpha Particle Spectrometer, the X-ray Spectrometer and the Gamma-ray Spectrometer.

Flight Plan page 3-316.

Flight Plan page 3-317.

Flight Plan page 3-318.

Flight Plan page 3-319.

Flight Plan page 3-320.

Flight Plan page 3-321.

Flight Plan page 3-322.

Rev 68 begins at about 210:02.

The 'Apollo 15 Index of 70-mm Photography' lists a sequence of 22 photographs as having been taken at any time between revolutions 64 and 72, the photo analysts having been unable to tie the exposures down more accurately. They were taken on magazine TT with a 60mm lens and are AS15-88-11985 to 12006. This seems as good a time as any to discuss these images.

As seen from Earth, the Moon is very near full and as a consequence, there are only about five minutes between Endeavour passing the terminator and AOS. Only limited photography can be achieved on the far side, so with magazine TT and the slightly wide-angle 60-mm lens, three images are taken during this short interval.

AS15-88-11985 looks towards the north and the Sun is shining from the west. Bottom right is Alden C which obliterates the north rim of Alden (shown better in the next frame). Beyond it (centre right) is the larger ring of Hilbert, and cut off on the far right is Kondratyuk, identified by two large craters within its walls. Beyond, and nearly at the horizon, is Meitner. At 168:06:09, Karl Henize asked Al to get an image of crater Alden and AS15-88-11986 would appear to be Karl's requested shot as the camera is tipped down to show it.

Alden is a highly degraded and obscured ring with its northeast rim completely destroyed by subsequent impacts that formed Alcen C and Alden E.

Just as the Moon appears nearly full from Earth, so the home planet reciprocates by displaying a striking crescent to the crew.

AS15-88-11988 and 11989 show an Earthrise which is very different to the Earthrise images which have been heavily publicised before because few reveal Earth in this repose. Cut off in the foreground of 11988 is Schorr, 53 km in diameter. The crater directly adjoining it to its southwest is in some atlases called Schorr A but in others Gibbs A. Beyond Schorr is the 77-km Gibbs and between the two runs a linear feature Catena Humboldt.

Under an overhead Sun, Plinius is the washed out circle in the centre of AS15-88-11990. Mare Tranquillitatis is in the foreground and the southwestern shore of Mare Serenitatis lies beyond.

AS15-88-11991 is taken from approximately the same position but looks northeast instead of northwest. The 30-km Vitruvius is to the right and in the foreground is Jansen D (at the edge of frame) and Jansen C, a 8.4-km simple crater now named Beketov after a Russian chemist, 1827-1911. Notice the irregularly shaped, vaguely looping dark area near the centre of the picture. In the foreground just in front of it is Mons Argaeus, a 50-km range of hills. A dark spur to its right is the Taurus/Littrow valley, destined to become the Apollo 17 landing site.

Excluding AS15-88-11994, which has no image, the next four frames, AS15-88-11992 to 11996, are all washed-out pictures of Aristarchus and Herodotus.

AS15-88-11997 to 11999 are further images of Earthrise which are somewhat afflicted by sunlight scattering in the window and lens. In the latter, Curie's western rim is in the foreground, the Schorr/Gibbs-A pair are at the extreme right and Gibbs lies beyond.

AS15-88-12000 and 12001 is of the Sulpicius Gallus region and the southwest rim of the Serenitatis basin, also known as Montes Haemus. The high Sun elevation makes the boundary between the mare and the Montes Haemus mountain chain difficult to see.

The final five images of this sequence all return to the western mare, particularly Aristarchus and Herodotus.

Flight Plan page 3-323.

This video may not be complete but shows a large part of the coverage at this point. It begins at 211:18:56 GET. Video is supplied courtesy of Mark Gray.

Karl Henize is reminding the crew, who have just awaken, of two items in the Flight Plan that occur soon after wakeup. First, they need to obtain the latest state vector that has been determined by the ground controllers. This can only be uplinked while the spacecraft is in contact with Earth, and there only a few minutes left before the Endeavour sails around the back side of the Moon. The request for rolling 40° is part of the maneuver to position the spacecraft for SIM bay observations with the CSM pointing forward instead of backwards. It makes the spacecraft avoid those attitudes that might cause gimbal lock while it maneuvers.

The computer uses P20 and the values entered into it to keep a particular side of the spacecraft pointing, in this case, at the centre of the Moon. Option 5 also includes an entry which defines the spacecraft's orientation about the theoretical line between the two bodies. When used for pointing the SIM bay, this latter value can define whether the spacecraft flies blunt-end-forward or, as in this case, sharp-end-forward (CM apex first).

This implies that science teams have been watching the results from the Mass Spectrometer and would like to gain more time in the sharp-end-forward attitude. Then the inlet to the instrument will aim away from the direction of travel and it is believed that any data in this mode will be due to outgassing from the spacecraft, not from any indigenous lunar atmosphere.

The steps that are being deleted are the procedures for starting a Mapping Camera pass. Flight Plan updates are necessary to manage spacecraft systems, or where from real-time analysis, new targets of opportunity are revealed. In this case, the update relates to problems with the Laser Altimeter. This instrument was to be used primarily in conjunction with the Mapping Camera where it would provide accurate altitude data for each frame by having the value optically encoded on the edge of the image. During night-side passes, the Mapping Camera would continue to operate so that even though no optical image was being produced by the Metric section of the instrument, the altitude information and the associated imagery from the Stellar Camera would still be gathered.

After a useful period of operation, the Laser Altimeter began to fail and is now considered a lost cause. While daylight use of the Mapping Camera still provides useful imagery from the Metric Camera, the defunct Laser Altimeter makes night-time operation a pointless exercise.

Verb 66 copies the CSM's state vector from its location in the computer to a second location normally used to store the LM's state vector. Normally, this is done when the CSM and LM are docked, to give the CSM's computer an initial idea of the LM's location. The reason why it is being done here isn't immediately obvious, but it seems to be a way to save the newly refreshed copy of the uplinked state vector.

Comm break.

In the rush of attending to chores before losing contact with Houston, Al has inadvertently left the computer uplink switch in Accept. This effectively prevents any other use of the computer.

Very long comm break.

During this far-side pass, the Mass Spectrometer experiment was to be turned off and its boom retracted. This task was deleted during the update immediately before LOS to give more data collection time in their current attitude. Indeed, this period of LOS is much quieter than originally planned because of the many deletions. The platform is to be realigned at 211:45 using Falcon's lift-off orientation as its primary reference. Aligning the platform is not only essential for navigation, but the accurate attitude information that results is critical for locating surface features photographed by the Panoramic Camera. The two-part Mapping Camera has its own independent attitude reference whereby the Stellar Camera images a starfield at 96° to the axis of the Metric Camera's optics.

Flight Plan page 3-324.

Rev 69 begins at about 212:00.

As the spacecraft coasts around the far side, the crew begins making breakfast.

By working back from the Mapping Camera start and stop times on the next rev (rev 70), the times that they coast over the terminator on this rev (69) can be inferred. By this, they should be crossing the sunset terminator about now, 212:22, at a longitude of about 114°E.

This alignment of the platform was done quite accurately. The true angular difference between the stars, whose positions are well defined, and as measured by the sextant sightings performed by the crew, give two values. Only 000.01° (as displayed by Noun 05) separated these two values. A low value is a source of pride, as it indicates that the sightings were done particularly well.

Flight Plan updates are a important part of the housekeeping for each revolution.

From the Apollo 15 Mission Report: "After rendezvous and with all three crewmen aboard the Command and Service Modules, the Flight Plan was updated to utilize the full capability of the Scientific Instrument Module bay. The Flight Plan changes were considerable, but with one crewman free to copy the updates, the other two crewmen were available to monitor and perform the Scientific Instrument Module activities. This meant that all three crewmen were utilized a good percentage of the time. The operation was performed satisfactorily and the real-time changing of the Flight Plan was accomplished without difficulty. The philosophy, that there would be no changes in the Flight Plan during solo operations, and that the Flight Plan would be subject to real-time change when all three crewmen were aboard, was satisfactory."

Originally, they were to use a 80-mm lens on Hasselblad, but the crew is to substitute a 250-mm telephoto instead. This change affects terminator photography at 124:02, where the science team wishes to get a closer look at the terrain. The change in lens type also affects the f-stop as the telephoto cannot achieve as wide an aperture as the standard lens. To compensate, the exposure time must be increased.

Comm break.

The changes to the Flight Plan are, in part, a continuing adjustment to the changes in Mapping Camera operation in light of the failing Laser Altimeter. Instead of being turned off, the camera is now to be turned on at 214:18:00, this being the start of a daylight pass. Terminator photos scheduled be taken starting at 214:13 were to coincide with the last few pictures in the original Mapping Camera pass. As the Mapping Camera is now scheduled to be started immediately after the terminator passed below, the back room wants detailed pictures of the terminator areas with a telephoto lens.

The call of "single tank capability" refers to an electrical power contingency mode. If troubles should occur that leave the spacecraft with only a single hydrogen tank and oxygen tank, the spacecraft can make it home if they power down to a 40-amp level. At a nominal 28 volts, this translates to a mere 1.1 kilowatts; about the same amount of power used for a stylist's hair dryer. Although this is a small fraction of the 4.3 kilowatts the fuel cells can generate, it provides for far more systems (and options) than the Apollo 13 crew had.

Endeavour's time in lunar orbit is drawing to a close and there is no point in bring unexposed film back to Earth so an intensive period of unplanned Hasselblad photography across the near side of the Moon begins with a sequence, AS15-97-13213 to 13229, taken over Mare Fecunditatis in support of Luna 16, a Soviet probe which soft-landed and returned a core sample to Earth just ten months before Apollo 15. These are taken using magazine O and a medium telephoto lens. This photography was held over from yesterday at 200:50 during rev 63.

AS15-97-13213 to 13216 have been combined into a single image.

Short burn constants are used, not surprisingly, for very short burns of the spacecraft's main engine, the Service Propulsion System or SPS. All engines have reasonably well defined startup and tailoff thrust characteristics that may last from milliseconds to several tenths of a second, as engines take a few moments to come up to full thrust, and thrust does not fall to zero at the moment the engine valves close at shutdown. In very short burns lasting less than a few seconds, the transitions from zero to full thrust, and from full thrust to zero, become a non-trivial part of the total impulse of the engine. The computer uses these constants when calculating the total time for the burn.

Accurately monitoring the progress of the burn is also a problem when its duration is very short. Although the computer updates the change in velocity every 1/10 of a second, and updates the entire state vector every two seconds, this is not sufficient to accurately determine the precise start and stop times of the engine. When a short burn constant is used in these calculations, an accurate burn is achieved, and very little manual trim is required from the crew.

Because of the problems with the intermittent short in the circuitry controlling the SPS's Bank A valves, all the short burns in lunar orbit will be performed using a single bank of valves, Bank B. While this does not significantly affect the performance of the engine when it fires for several seconds, the startup and shutdown characteristics change quite a bit. Engineers from Aerojet General, the manufacturer of the engine, have calculated the new engine characteristics based on its operation seen so far in the flight, both in dual-bank and single-bank operation. This information has allowed them to recalculate the short burn constants, which will be used for the rest of the mission.

Comm break.

Photography continues on magazine QQ with black and white film and using the 500-mm telephoto lens. The first in this sequence is AS15-81-10987, an unremarkable patch of Mare Fecunditatis dominated by an unnamed elongate crater.

The following six images take alternate shots of two of the most extraordinary elongate craters on the Moon, the Messier twins.

A context image from the Lunar Reconnaissance Orbiter helps to show why these two craters were of great interest to geologists.

The current favoured theory is that a double asteroid impacted the Moon at a very shallow angle. Each impactor gouged out its own elongated crater and the extreme angle produced the very unusual ray system. This system is dominated by two narrow rays that run westward across the mare. A fainter broad ray set of rays appear to perpendicular to the long axis of Messier.

An interpretation of the PAD follows:

• Purpose: This is the next-to-the last in the series of abort PAD that are sent to the crew in the event of communications breakdown or problems with the spacecraft, this one based on an ignition towards the end of Rev-71.
• System: The maneuver would use the Service Propulsion System, the main engine with 22,500 pounds of thrust, under the control of the primary Guidance and Navigation system.
• CSM Weight (Noun 47): is not applicable as the current weight is assumed.
• Pitch and yaw trim (Noun 48): +0.64° and +0.98°. These are the angles to which the SPS engine must be aimed to align its thrust axis with the spacecraft's centre of gravity.
• Time of ignition, T_IG (Noun 33): 217 hours, 49 minutes, 18.04 seconds.
• Change in velocity (Noun 81), fps (m/s): x, +2,838.6 (+865.2); y, -581.0 (-177.1); z, -27.7 (-8.4). Velocity components are expressed with respect to the local vertical frame of reference.
• Spacecraft attitude: Roll, 178°; Pitch, 129°; Yaw, 351°. These attitudes are expressed with respect to the lift-off REFSMMAT.

The final note in the PAD states that SPS propellants should be settled in their tanks by firing the plus-X thrusters on all four of the Service Module RCS quads for 12 seconds.

Comm break.

This Mapping Camera PAD puts some numbers into the earlier change at 212:34:09 whereby a planned T-stop time was converted into a T-Start time.

At around this time, a photo is taken with the medium wide-angle (60-mm) lens looking northwest towards Mare Tranquillitatis.

The camera used for this image has been brought up from the lunar surface and its Réseau plate (serial number 38) has been heavily contaminated, hence the dark marks on the right of the image. The U-shaped artefact lower right is a reflection in the cabin window of one of the spacecraft's fluorescent lights. In the foreground is a small mountain range, Montes Secchi, and the crater after which the range is named. Pietro Angelo Secchi, 1818-1878, was an Italian astronomer who pioneered the use of spectroscopy to analyse the chemical makeup of stars. In this picture, the very high Sun elevation makes the crater virtually invisible. The dark bay at the top of the photo is Sinus Concordiae which leads off the northeast edge of Mare Tranquillitatis.

The next photography takes place over the southern shore of Mare Tranquillitatis. There are four shots of Censorinus and one of the 24-km crater, Maskelyne.

Of the two craters in these images, it is the smaller, at only 3.8 km in diameter, that carries the name Censorinus by virtue of its brightness and visibility from Earth at high illumination angles. The brightness reflects its relative youth. The 7-km Censorinus A beside it probably once looked much like its companion, but over a large fraction of an aeon (an aeon being one billion years) or more, the lunar environment has darkened its ray system to invisibility.

Censorinus was often considered as a possible site for the more limited Apollo H-class missions once Apollo 12 had proved that pinpoint landings were possible. Had Apollo 13 not aborted and budget cuts not converted Apollo 15 to a J-class mission, Censorinus might today have a spent LM descent stage sitting nearby, very likely the same one that now hangs in the Apollo/Saturn building at Kennedy Space Center, Florida. Instead, Apollo 14 visited Fra Mauro to the east and subsequent missions moved on to the multi-objective J-class missions, of which Apollo 15 is now the first.

Censorinus was interesting to Apollo planners because it is a fresh crater from a meteorite which had driven into an ancient terra landscape. It is a happy fact of crater formation that the distance of ejecta from a crater is related to the depth from which it was hauled by the impact, with the deepest material being deposited on the rim. By radially sampling an ejecta blanket going towards a crater, one can lift rocks brought from successively deeper layers below. An image from Lunar Reconnaissance Orbiter helps to give the context of Censorinus.

This large-scale image shows that south of Censorinus is Mare Nectaris (Sea of Nectar). An arc-shaped scarp to its west, Rupes Altai, betrays the truth that the Nectaris basin is a much larger structure than Mare Nectaris. The scarp is part of the Nectaris basin rim and Mare Nectaris is just where lava only managed to full the central ring. Censorinus just happens to lie at the northern extreme of this basin and therefore provides a convenient drill-hole into the rim of the Nectaris basin. If a crew had been able to sample its ejecta, a rich record of one of the earliest major impacts might have been recovered.

The other image taken at this time is AS15-81-10998, which looks straight down into the 24-km, frame-filling crater, Maskelyne. The right of the picture shows some slumping of the crater walls. A central peak rises from the floor but is indistinguishable in this image. Nevil Maskelyne, 1732-1811, was the fifth Astronomer Royal of Britain at a time when one of the main goals of astronomy was in aiding navigation around the globe. He was involved in assessing the accuracy of various designs of chronometer which would help ships determine longitude while at sea and he is also noted for determining the density of Earth.

Lee Silver led the training of the crew for their geological exploration of the Moon. Jim Head was primarily involved in the analysis carried out by Bellcomm on NASA's behalf to select a site and study the logistics for its exploration. Both men were part of the science backroom team interacting with Dave and Jim while on the surface and with Al during his solo mission. As they did for many of the geology team, the crew named features at the Hadley landing site in their honour. Silver Spur is an apparent peak 20 km SSE of the landing site which fascinated geologists for its layering, and everyone else for its beauty. Head Valley, seen in this annotated view of the landing site, is actually that part of Rima Hadley where it runs along the base of Mount Hadley Delta before turning North at Elbow Crater.

Long comm break.

Taken around this time is AS15-81-10998, which looks straight down into the 24-km, frame-filling crater, Maskelyne.

The top of the picture shows some slumping of the crater walls. A central peak rises from the floor but is indistinguishable in this image. Nevil Maskelyne, 1732-1811, was the fifth Astronomer Royal of Britain at a time when one of the main goals of astronomy was in aiding navigation around the globe. He was involved in assessing the accuracy of various designs of chronometer which would help ships determine longitude while at sea and he is also noted for determining the density of Earth.

About four minutes later and the spacecraft has coasted across Mare Tranquillitatis. In image AS15-81-10999 and looking far to the SSW, the crater Dionysius is photographed using the 500-mm lens and magazine QQ.

From Earth during the full Moon, the 17.6-km Dionysius appears quite bright as a spot at the southwest shore of Mare Tranquillitatis. The appearance of the crater and its striking, classic ejecta blanket in this photograph shows why. Notice the transition from the continuous to the discontinuous ejecta blanket at about one crater-diameter from the rim.

AS15-81-11006, 11007 and 11008 are all views into the 27-km crater Menelaus. Living about 100 AD, Menelaus was a Greek astronomer and geometer. The crater named after him is situated at the southeastern end of Montes Haemus on the rim of the Serenitatis basin.

These shots were taken using the 500-mm lens whereas AS15-90-12294, taken with a 60-mm lens, shows the crater in context with the southwestern shore of Mare Serenitatis and the Sulpicius Gallus region.

Comm break.

The crater Henize is referring to is actually a 15-metre crater southeast of Scarp. It became Station 9 during the third EVA and attracted Dave and Jim's attention because of its blockiness and freshness. A pan of the crater and its environs has been constructed from AS15-82-11066 to 11092 by David Byrne and shows the crater to the right and the large amount of debris scattered in and around it.

A bench structure, visible left of the crater's floor, is what interests the geologists most. Normally a bench indicated that the crater has uncovered a subsurface layer. However, the soft, fragile clods of breccia around the crater's rim indicate that it never got past the regolith which is the thick layer of debris that covers everywhere on the Moon. While studying it, Jim had noticed the amount of glass covering the rocks at or below the bench and surmised that this crater was a larger version of the many small craters they had seen which have a pool of solidified melt glass at the bottom. His observation turned out to be correct. The crater had not hit bedrock and instead the shock of impact had produced a ring of glass which welded the clods of rock together to form the bench.

As the above conversation is taking place, photography is continuing and will do for the next 20 minutes, most likely taken by Al. Four photos, AS15-81-11009 to 11012, are taken on the black and white magazine QQ with the 500-mm lens of an area beyond the rim of the Serenitatis basin called Montes Haemus.

This bright craterlet is within an area of mare material adjacent to Lacus Gaudii (Lake of Joy).

The next three show another bright craterlet, this time 57 kilometres WSW of Sulpicius Gallus.

On colour magazine O using a 250-mm lens, photos AS15-97-13230 and 13231 look north across the western shore of Mare Serenitatis towards Montes Caucasus.

The spacecraft is approaching the Apennines and the landing site and a frame, AS15-97-13232, is taken looking forward and north to Rima Hadley.

Mount Hadley Delta is on the right with the landing site just beyond it. The source of the rille, the arcuate cleft, Béla, is at the extreme bottom left.

On magazine PP, two frames, AS15-90-12295 and 12296, are taken of the same view of the Apennine range but with a 60-mm lens.

The bright crater is Aratus and the darker crater to its lower right is Galen, a 10-km bowl named after a Greek physician, Galenos, c. 129-200 AD and formerly known as Aratus A. Extend a line from Galen to Aratus and the same distance beyond and you come to Mount Hadley Delta and the landing site.

Going from the wide-angle to the 500-mm telephoto lens, AS15-81-11013 is a somewhat indistinct view of one of the most unusual features on the Moon, Ina.

As shown by the above image from Lunar Reconnaissance Orbiter, Ina is clearly very different in form to just about everywhere else on the Moon and its appearance has raised some controversies about its origin. Recent theories suggest that it shows signs of relatively recent volcanism; i.e. less than 100 million years ago, which in lunar terms is almost current. This is largely based on the technique of crater counting whereby the record of impact can be used as a proxy for time. However, others point out that this technique may have been skewed because the basalt that comprises the feature seems to have been formed from a gas-rich, foamy lava. The porosity of such a basalt would so profoundly affect the formation of craters that it would alter their size and apparent distribution and thereby affect the feature's apparent age. Compensating for this effect would make the feature be as old as the surrounding mare, at about 3.5 billion years. There is another similar feature 47 km west of the sunken crater Maskelyne F in Mare Tranquillitatis, a photograph of which was taken as AS15-92-12519 during Rev 71.

Two shots are taken on magazine PP with the wide-angle lens that show the Montes Apenninus range in high Sun, including crater Conon.

Flight Plan page 3-325.

A small but rather touching moment ensues when Lee Silver becomes the only non-astronaut geologist to speak to a crew during a flight.

Very long comm break.

David Woods, from 2004 mission review: "In this conversation, you are very vocal about human exploration of the Moon. The Moon nowadays is sidelined by many in the planetary sciences world. You suggest here that having humans wander about the surface, being geologists, is a great thing. In the present environment [in light of the 2004 Bush Moon/Mars plan] do you think it's still a great way to go?"

Scott, from 2004 mission review: "Yeah, especially for a geologist. If you're a geologist, it's a great place to go. If you are trying to collect science and you don't have any money, you send a robot. The variables in that equation are about ten. So if you want to solve that equation, you have to put all the variables in there. It's not that simple. It'd be great, go back and everybody have an opportunity to go, do geology on the surface of the Moon, given unlimited budgets, unlimited technology. Just like if you want to go out in someplace on the Earth and do geology and you can get your four-wheeler somewhere and drive out into the mountains or the fields or - geology started in England, yeah? Drive out there and spend a couple or three weeks, terrific. Got your petrol, got your tent, got some fire? Got your boots, your hammer? Head on out there. Same thing on the Moon. Gee, if you're gonna go out there and do it, do it! That's what I'm saying here. I'm not looking at all the other elements of the equation."

The birth of geology as a science is generally attributed to James Hutton, an Edinburgh-born farmer and part of the Scottish Enlightenment of the 18th century.

David Harland, from 2004 mission review: "It's also seeing it from the perspective of the time."

Scott, from 2004 mission review: "Sure. But I'd still say the same thing."

Woods, from 2004 mission review: "It was a time when it was thought it was possible. It was a time when we felt it ought not to be long to a return."

Scott, from 2004 mission review: "It's part of a general discussion. It not a programmatic debate or a project pitch to try and sell anything. It's sort of like what's there, what would you like to do? I'd like to do a lot of things."

Harland, from 2004 mission review: "Yours was the first science mission and you're talking to your mentor and you're just being very enthusiastic saying it was a good thing to do and we should keep doing it and there are plenty places to see."

Scott, from 2004 mission review: "Plenty. And the point is that there's lots of variety on the Moon. All the landing sites we didn't go to as an example. And all the landing sites we could have gone to. Tycho and Tsiolkovsky and, I mean there's fabulous places that nobody had been to that have great variety. But, you couldn't do them all in Apollo, obviously. You were limited to a band around the middle - couldn't get down to Tycho - and the surface areas were questionable. That's why we had all these debates on landing sites. Had to factor all the issues in there to decide where to go. But I'd say, yeah, that's great, go. Bring everybody up here!"

Woods, from 2004 mission review: "How do you reply to people that describe the Moon as a useless ball of dirt? Would you argue with that outlook?"

Scott, from 2004 mission review: "Of course. I mean, it's not a useless ball. It influences a lot of things on the Earth. Without the Moon, we wouldn't have the Earth as it is. Right? So the Earth-Moon system really creates the environment in which we live."

Woods, from 2004 mission review: "But as a place to go and visit, either by humans or remotely."

Scott, from 2004 mission review: "Well, you know, the more you learn about the Solar System, the more you learn about the Earth, the more you learn about yourself, and humans and where they live and how they live in the environment. We did, in the whole discussion - in fact we've just been going through quotes for the book ['Two Sides of the Moon', David Scott and Alexei Leonov with Christine Toomey, 2004, Simon & Schuster] and found a good one by Socrates. 'The only way you're going to understand the world in which you live is to get above the atmosphere and look back at it.' Kinda paraphrased. So I think those who say it's a waste to go to the Moon don't really understand, or else they'll choose to think about the environment and the way the Earth was created, if you will, and the influence of the Moon and what we learn by going into the Solar System, about ourselves, about the Earth, and it sort of goes on and on and on. But that's why, if somebody says the Moon is a worthless ball of dust, I say 'OK, fine. If that's all you're interested in, if that's all you know about it, fine. Choose your path.' And I don't really have a lot of time for them. You're not going to convince them and if you get into a big debate and they argue about it, I don't have any time for that."

Woods, from 2004 mission review: "But it's useful to know what you think of it, what your point of view is. It's interesting, as someone who has been there and who has invested an important part of their life in that exploration, it's interesting to know how you view exploration."

Scott, from 2004 mission review: "Oh yeah. But, you know, I'm only the sort of point of the pyramid because all 400,000 people who worked on it probably think the same. And you guys do too, for it's worth doing because it's worth learning about who we are and how we are and how we live and people who take the opposite view; that's OK, they get their choice, you know, and they can view it that way if they want to but I would suggest they spend a little bit of time trying to understand more about the scientific aspects, the geology, etc., and just the spirit of exploration. Why people do this. Why people go out and, you know, fly in the sky and plunge to the depths of the ocean and go to the Moon and all that. It's adventure and that's why humans are humans."

Woods, from 2004 mission review: "Adventure and knowledge."

Scott, from 2004 mission review: "Yeah."

Woods, from 2004 mission review: "Thank you for that."

The best recording of the following PAO announcement has a music track bleeding through. It may be that there was a bit of unintended crosstalk between audio feeds while someone in the Public Affairs department was enjoying some entertainment.

This exchange was portrayed in 'Mr Galileo Was Right', the Apollo 15 episode of Tom Hanks' excellent From the Earth to the Moon TV series, made in 1998, on which Dave served as a technical adviser.

There is no more communication until after the spacecraft has passed the terminator. However, there is a lot of photography taking place. Returning to the long lens and magazine QQ, there are more shots of details around the Apennine Bench Formation.

AS15-81-11022 is a spectacular view across Mare Imbrium. In the foreground is Montes Spitzbergen, and rising out of the horizon is the Beta Prominence, an isolated minor hill about 70 km south of Mons Pico. These hills, along with two other ranges to the northwest, are believed to be remnants of an inner ring of the Imbrium Basin.

Using a 250-mm lens and colour film on magazine O, AS15-97-13233 and 13234 look northeast over the 83-km ring of Archimedes towards Montes Spitzbergen.

These two frames have been combined into a single image.

Rima Vladimir and Rima Bradley are covered by four images from AS15-97-13235 to 13238.

Both rilles are more clearly seen in 13236 with Rima Bradley running from right-centre to bottom-centre.

The four depressions that run along Rima Vladimir have names that ring a bell with those who study Apollo. When Mike Collins orbited the Moon on Apollo 11, he announced that he was naming a 138-metre crater that he was using as a navigation landmark in honour of his children and wife; Kate, Ann, Michael and Patricia; hence KAMP. Mike's suggestion for this crater in Mare Spumans has not been recognised by the IAU. However, it is notable that the same names have been applied in the same order to these four depressions along Rima Vladimir.

Returning to the longest lens, the next sequence of photos is frames AS15-81-11023 to 11026. These show MacMillan, formerly known as Archimedes F, and its environs. This 7.5-km crater is named after William Duncan MacMillan, 1871-1948, an American astronomer and mathematician.

At around 213:05 using magazine O and the 250mm lens, and moving towards the centre of Mare Imbrium, two photographs are taken of Timocharis.

These have been combined to show three quarters of this prominent crater's rim.

The terracing or scalloping around the rim is a classic example of what happens to the walls of large craters which are unable to retain the original bowl shape that smaller craters exhibit. These are essentially large scale landslides. The crater also has a small crater-like depression at its centre where a central peak would normally be expected.

These last targets for the crew's cameras, plus a few others, are captured in more detail by near simultaneous photography using magazine QQ and the 500-mm lens. AS15-81-11027 and 11029 are of a little triangular hill that lies between Timocharis and Lambert. These isolated hills, including Mons La Hire, are a feature of Mare Imbrium and are thought to be traces of the original multi-ring structure formed directly by the impact that created the Imbrium basin.

AS15-81-11028 is another little hill between Timocharis and Lambert with a distinctive triple peak.

Lambert exhibits an unusual asymmetry in its ejecta blanket which is shown in detail in 11030 and 11031.

Compare this shot to AS15-97-13242, taken with the 250mm lens, which shows it in context with the crater rim. This ejecta "spur" may be traces of a wrinkle ridge that Lambert just happens to lie upon.

There are two further sequences in magazine QQ before it is fully exposed. Al took particular interest in the area when he observed it under low-angle illumination on the third day of his solo mission after noticing traces of lobate margins to lava flows. The first sequence is AS15-81-11032 to 11036, which show the two small craters, La Hire A and La Hire B, and the part of Dorsum Zirkel that runs between them. These craters are about 50 km from Mons La Hire and crater A is distinguishable by the little "rim-shot" crater on its northern rim.

These five images have been composited.

The sequence along Dorsum Zirkel is repeated.

Mons La Hire is shown in images AS15-81-11041 to 11043. In the oblique sunlight Al first saw them by, he was struck by the crater-like depressions along its northern flank which gave him a sense that he was looking at the remains of a volcano.

These three images have been composited.

The sequence along Mons La Hire is repeated until magazine QQ runs out of film.

Now that magazine QQ is finished, subsequent photography on this rev is carried out using PP and O. Dealing with magazine O first and the 250mm lens, a photograph of the whole of Mons La Hire is taken.

The next photo on magazine O is a patch of eastern Mare Imbrium with Dorsum Zirkel passing to the right. This is taken at around 213:10 GET.

Using colour film in magazine PP and its wide-angle lens, AS15-90-12299 begins a sequence of four images which allow the spacecraft's motion to track the camera across the western Mare Imbrium. The contamination on the Réseau plate of this camera is very apparent.

The camera is tipped up to the horizon in AS15-90-12300 so that the 16-km crater, Gruithuisen comes into view. Beyond and near the top of the picture is Mons Gruithuisen Gamma. This image does not show it well but it is an interesting dome-like structure with a 900-metre craterlet at the top.

These photographs illustrate one of the features of lunar illumination which is rarely seen on Earth, the "zero-phase" which is the bright spot to the lower left next to the crater Angström. This author (Woods) has noticed the same effect while flying on a sunny day over a dew-covered grassy field. It is always seen on the Moon at a point exactly opposite the Sun for the observer. Part of the reason for it is, like the dew on the grass, the presence in the lunar regolith of countless tiny beads of glass produced over the aeons by the incessant pounding and melting of rock when rocks fall from space. A fraction is also due to glass that was sprayed out during early volcanic processes. Another mechanism that only came to light in 1986 is coherent backscatter, a subtle quantum effect that increases the intensity of the zero phase. This zero-phase light proved very uncomfortable to surface crews when they had to walk or drive away from the Sun. Notice how, by AS15-90-12302, it has "moved" with the spacecraft. In this latter frame, the 9.8-km Angström is in the foreground and the complex of craters centred around Krieger is plainly visible beyond. The single crater this side of zero-phase is Wollaston. Next to Angström is the dim outline of a ghost crater about 7 kilometres across. This would have been formed just before the final deluge of runny lunar lava passed this way filling the bowl and leaving the crater rim sitting proud of the mare surface.

The camera moves to a different window to gain a view more directly downwards.

This frame manages to capture an unusual feature part way along one of the Prinz rilles which journal contributor John Pfannerstill has named The Paperclip.

With excessive hubris, this author (Woods) has come up with a formation mechanism for The Paperclip. Since the 1994 impact of comet Shoemaker-Levy 9 into Jupiter, there has been a better understanding of how tidal forces can disrupt a small, loosely aggregated body as it makes a close passage by a large planet. The differential gravitational field separates the constituents of such a body to form a string of possible impactors. If these then happen upon a larger world, be it a moon or planet, they will impact, one after the other. Of course, the larger body has its own rotation so it is expected that the resultant impacts will be spread apart on the surface, depending on how fast that rotation is and how far apart the impactors had drifted apart prior to impact. A few of the crater chains on the Moon that don't have an association with lava rilles are likely to have been formed this way and the Davy Rille (Catena Davy) near the centre of the near side is now thought to be a good example. I would propose the same mechanism for The Paperclip, that a string of objects came barrelling in to produce a row of similarly-sized overlapping craters in a mare landscape that was still being formed. This would have occurred three or more billion years ago when great outpourings of the Moon's runny lava would have been common. A river of such lava happened to be running right where the crater chain formed and its lavas inundated the chain, filling the craters and melting away any sign of their separate identities as it helped to form Oceanus Procellarum.

The Paperclip also appears in image AS15-90-12304 but is partly obscured by the dirt on the camera's Réseau plate.

At about this time (213:15), a colour image is taken on magazine O with the 250mm lens.

This shows the area just north of Krieger, whose ejecta blanket is visible at the very top-left corner of the image. Two wrinkle ridges run north across the image (north is to the right). These features are signs of the stresses within the basalt beds of the mare. As the bulk of the dense basalt sinks unequally, some areas sustain compressional forces which causes upthrust along points of weakness. As they protrude above the surrounding surface, they are collectively called "dorsa".

The next image on magazine PP is an image framed in the window of the main hatch that was used in the astonishing book, 'Full Moon' by Michael Light, who has kindly donated this version to the Journal, this being number 28 in his collection. Light has processed his version heavily to increase its contrast, remove the Réseau plate dirt and remove the reflections of the cabin lights in the window.

On the original scan, north is to the left and the large crater is Krieger at 22 kilometers in diameter. Interrupting its southern rim is Van Biesbroeck, a simple 10-km crater. The two craters to the east are Rocco (the larger crater) and Ruth. Note the rille that runs from a breach in the western wall into Oceanus Procellarum. This is Rima Krieger. As was thoroughly documented during yesterday's photography, this area, the Aristarchus Plateau is very rich in rilles. AS15-90-12306 takes the viewpoint away from Krieger somewhat to the craters north of Aristarchus which are the source of some of these rilles, the Rimae Aristarchus.

The crater to the right of the rille-producing pair is Toscanelli. The remaining ten frames on magazine PP for this pass follow slightly to the west of Toscanelli across the northern edge of the Aristarchus Plateau to Montes Agricola, finally settling on its northern end.

Simultaneously with these wide-angle images in and around the Aristarchus Plateau, another crop are being taken of this rich area using colour film and the medium telephoto (250-mm) lens. These are AS15-97-13246 to 13265.

These three can be composited.

Linear features that are sunken are called "rima" and these images, AS15-97-13246 to 13248 show examples of this type, particularly Rima Archimedes VIII running from bottom-left in this composite. This author (Woods) believes the large cleft to the left is the inundated remains of a much older and wider rille which may have been somewhat similar to Vallis Schröteri which the crew will photograph soon. Part of Montes Agricola is seen running across the next pair of photos, AS15-97-13249 and 13250. The northern edge of the Aristarchus plateau runs along the bottom of 13249.

These two have been composited.

The photography now looks northwest across Oceanus Procellarum. Of much interest to lunar geologists before Apollo were the "special features", odd landforms that were outside the ordinary when looking at the Moon. Only later would the collective mind of science realise that much of the important story of the Moon can be deduced by looking at the big picture - the maria, basins and terra - and the impacts that modelled them. Mons Rümker, seen among the next three frames, AS15-97-13251 to 13253, is an example of a special feature. It is a collection of low volcanic domes in the northern regions of Oceanus Procellarum named after a German astronomer Karl Ludwig Christian Rümker, 1788-1862.

These three images can be composited together.

Frames AS15-97-13254 and 13255 look further to the west at the terminator.

A composite of these two frames shows the 9.6-km Naumann at the bottom and the complex of wrinkle ridges that cross Oceanus Procellarum.

As Endeavour passes over the Aristarchus Plateau, a crewmember, probably Al, takes one of the most spectacular sequences of Hasselblad photographs from the mission. The eight frames in this sequence look approximately south to show the full 160-km length of Vallis Schröteri from its source in the so-called "Cobra Head" on the left to where it fades out in Oceanus Procellarum.

These have been composited.

The valley is visible from Earth with even a small telescope but it took spacecraft to reveal the smaller meandering rille within. When compared to the bulk of the rille, the Cobra Head is very heavily pitted with craters. These are secondary impacts from the ejecta thrown out by Aristarchus a few dozen kilometres to the left and much younger than the rille. While Schröter's Valley is about 3 aeons old, Aristarchus' age is "only" about ½ an aeon or less. The composite was produced from frames AS15-97-13256 to 13263. Paul Spudis is a geologist at the Lunar and Planetary Institute in Houston and we discussed the sinuous rilles.

Paul Spudis, from 2000 correspondence: "Basically, these are lava channels, formed during eruption of the mare basalts. There is currently a debate about whether the rilles are constructional features (i.e., that they are built up by lava overplating, as here on Earth) or if they are erosional features (hot, runny, turbulent lava actually erodes the Moon's surface.) It may be that different processes are of differing importance in different rilles."

The final images in this series are of a wrinkle ridge, Dorsa Whiston, which runs across Oceanus Procellarum south of the small crater Humason (formerly Lichtenberg G).

Both have been composited to show a greater contigious length.

These are the last images from this daylight pass and the spacecraft passes the sunrise terminator at about 213:21.

Long comm break.

Comm break.

Very long comm break.