*\[Jones - \"Because you had to land, what, within a day of
sunrise.\"\]*

*\[Mitchell - \"Yeah. We only had a few hours of lunar day latitude with
respect to angle on the Sun. We had to land at 7 or 8 o\'clock in the
morning lunar time to get the Sun angle - what? - above 12 degrees and,
as I recall, 15 degrees.\"\]*

*\[Jones - \"And it\'s 12 degrees per day, so that\'s pretty tight. And
it\'s basically for shadows? Shadows long enough that you can see
definitions but not so long that you\'re overlapping and obscuring
things.\"\]*

ZERO PHASE

*\[Mitchell - \"Looking directly down-Sun. It was a phenomenon that had
been observed, I guess, as far back as Apollo 11. And no one quite
understood why things were disappearing in front of them - or, seemed to
be disappearing. And they started calling that zero-phase and it was
having the Sun angle precisely behind you. And, frankly, I don\'t recall
the physics of it, why that turned out to be so. It was just a fact.
Things washed out ahead of you and you just couldn\'t see it. It\'s kind
of like snow-blindness in a way.\"\]*

*\[Jones - \"Part of it is the shadows are disappearing because, with
the Sun low behind you and you low to the ground, whatever objects are
casting shadows are hiding their own shadows.\"\]*

*\[Mitchell - \"Well, that\'s quite true. That\'s part of it. But I
don\'t think the total explanation.\"\]*

*\[Jones - \"There may also be a fair amount of back scatter.\"\]*

*\[Mitchell - \"And it may be the combination of the two.\"\]*

*\[Jones - \"And the uniform color.\"\]*

*\[Mitchell - \"The uniform color definitely adds to it. Yeah, you\'re
right. On either side of it, even with a large object, you\'d be looking
around the object instead of over the object to the shadow.\"\]*

*\[The process chiefly responsible for the brightness of zero-phase is
called [Coherent
Backscatter](http://www.hq.nasa.gov/office/pao/History/alsj/coherentbcksctr.html).\]*

\[Shepard, from the 1971 Technical Debrief - \"Certainly, it\'s
advantageous to land in those low Sun angles. We had practiced at higher
ones, and I don\'t think that a Sun angle of, say, 1 day later - 15
degrees higher - is prohibited. But it could be prohibited from the
standpoint of visual acuity if it were combined with looking down-Sun.
If you were to come in without the Sun displaced off the approach track
and with higher Sun angles, you might have a problem, in earlier
assessment of
[LPD](http://www.hq.nasa.gov/office/pao/History/alsj/apollo.glossary.html#LPD)
corrections. Jack (?) said we were 14 degrees off (the Sun line) and we
had no problem with zero phase. Certainly, any more than that (14
degrees) is fine. Now, whether you can come up with any magic formula
that says as long as you\'re outside of a cone of less than, I don\'t
know, 6 or 7 degrees in elevation and azimuth with respect to
zero-phase, it\'s probably okay. That would be a ballpark guess. I think
you\'d probably want to look at the zero-phase photographs to figure out
what kind of angle you have to have in all directions to describe the
cone - the combination of horizontal and vertical angles. You find that,
outside of that cone, the eyeball\'s ability to discern features is good
enough.\"\]

ZERO-G BUTTS

*\[Mitchell - \"Well, there\'s a couple of things apropos to what
you\'re saying. For example, there was a difference that immediately
occurred on the flight, right after launch. I was sighting in the
Command Module telescope to align the platform; and, from training, I
was used to sitting on the CMP seat and having the telescope be right
about eye level. In flight, there was a small but important difference.
I suddenly found that, instead of the eyepiece being in the normal
position, it was down at around my mouth. Why? Because one g compresses
your butt and your clothing and you sit on the seat lower than you do in
zero-g. In zero-g, nothing compresses and your natural position is an
inch or so higher. And it\'s those little things that are surprises.
They waste your time. You realize why, very shortly, but you spend from
a split second to a few seconds figuring out what\'s different. You get
in the spacecraft and, on your first time at the telescope, you find
it\'s down here. Well then, from that point on, you\'re spending your
time holding yourself down against the seat so you can have the right
eye level. It\'s one of those little surprises that are always going to
be there. Your body\'s trained, your thinking\'s trained, your movements
are trained to do one thing and, suddenly, it\'s off by an inch or two.
Similar to that, in the zero-g environment, we noticed - and I don\'t
know about other crews, I think they probably noticed it too - that
after we\'d been in space for 24 to 48 hours, we noticed low back pains.
Why low back pains? It took me two days to figure out what it was. I
observed that the pain changed when I squeezed my toes. And then I
suddenly realized that, in zero-g, the first thing that happens when
you\'re floating around or you\'re trying to maintain position and
suddenly you find yourself drifting, the first thing that happens is
that you squeezed your prehensile toes. The old reptilian brain, to
stabilize you and hold you in place, was squeezing toes. Does that go
back to monkey days? Probably. But it occurred to me, after a while,
that that\'s where that damn back pain was coming from. Tensing up to
try to maintain position when you started to float away, was a natural
reaction. And, after a day or so, it was causing intense back pain. And
it took time to figure out. \'What the hell\'s going on here? Why am I
getting back pain?\' But, suddenly, you connect the back pain with
squeezing of toes. Reptilian brain\...Well, maybe not reptilian brain.
It goes back there to swinging through the trees, I guess. And those
things sort of crop up. Interesting science, interesting observation.
But, as far as operations are concerned, it takes your time and it\'s
part of the learning process.\"\]*

**115:39:44** McCandless: And why don\'t you give us EMU status check
before you set out?

**115:39:50** Mitchell: Okay, the LMP is reading 3.75 (psi), and about
55 percent (oxygen), (pause) medium to low cooling. Feeling great.

**115:40:10** McCandless: Okay. Say again the percentage, Ed.

**115:40:16** Mitchell: It looks like I\'m reading 50\...No, sorry about
that. (Pause)

**115:40:25** Shepard: Man, it\'s hard to see.

*\[The oxygen gauge is on top of the RCU, about in the middle. The gauge
is recessed and, therefore, is usually in shadow. Add a little dust on
the gauge and it becomes very hard to read.\]*

**115:40:26** Mitchell: Yeah. I\'m reading 55 percent, Bruce.

**115:40:29** McCandless: Roger.

**UP TO YoUR ARMPITS**

**115:52:31** Mitchell: Think you ought to press a little\...bear a
little to the left, Al.

**115:52:33** Shepard: Yeah. I guess we\'ll have to. (Pause) Nothing
like being up to your armpits in lunar dust! (Pause)

BOYD BOLTS

**116:09:00** Shepard: Another one of those beautiful (pause) Boyd bolts
is all full of dust.

**116:09:10** Mitchell: Yep. That\'s not (surprising). Everything else
is going to be full of dust before long. Be filthy as pigs.

*\[The Boyd bolts hold the various experiment packages firmly in place
on the ALSEP pallets. Each bolt is recessed in a sleeve used to guide
the Universal Handling Tool (UHT) onto the bolt. Once the tool has
engaged a bolt, the astronaut gives it a turn to release the bolt. Al is
reporting that one or more of the Boyd bolt sleeves holding the SIDE on
the subpallet is full of dust. Ed tosses something toward the MET,
probably a no-longer-needed piece of mounting hardware or a protective
cover.\]*

**116:09:17** Shepard: Okay. I\'m going to have to lift this (SIDE
subpallet) up. You want to help me?

**116:09:20** Mitchell: (Joining Al at the subpallet) Okay. What you
want to do?

**116:09:22** Shepard: I\'m going to have to lift it up and shake the
dust out of that Boyd bolt; I can\'t get it otherwise.

**116:09:26** Mitchell: Okay. (Long Pause) (Garbled)

**116:09:40** Shepard: Not yet. There we go. Okay, watch that\...

**116:09:48** Mitchell: Is there anything that\'s not tied on?

**116:09:49** Shepard: That\'s loose, yeah. I\'ve already taken those
out.

**116:09:51** Mitchell: Okay, I\'ll hold it. (Pause)

*\[They are standing facing each other, with Ed on the right, holding
the subpallet between them at about waist height. When they are standing
close to each other, their images merge and saturate; but, here, they
are well separated and we can see them turn the subpallet upside down to
get the dust out of the Boyd bolt sleeves.\]*

**116:09:57** Shepard: Okay. Let\'s just turn it upside down and shake
it.

**116:10:05** Mitchell: Well, there\'s a lot of Boyd bolts falling off.

**116:10:08** Shepard: Yeah, but them\'s (sic) not the ones we\'ve got
the problems with. Okay, flop it over a minute. (Pause)

**116:10:18** Mitchell: That\'ll do it?

**116:10:20** Shepard: No, it\'s still not clear. (Pause)

*\[Mitchell - \"That Boyd bolt was one that was buried (that is,
surrounded by equipment) and it was in a protected housing.\"\]*

*\[Ed used his hands to indicate that the sleeve was about two inches (5
cm) long and the outer diameter was about the size of a 50 cent piece -
about 3 cm.\]*

*\[Mitchell - \"You had to get the tool down in there and, as I recall,
it was a twist to release it and, apparently, that was packed full of
dirt. Now, Al was looking at it, trying to see it. And he couldn\'t get
the tool in and couldn\'t get it released - and couldn\'t see it.
Remember that, on the lunar surface, there\'s no air to refract the
light in there. So, it\'s either shadow or it\'s light and, unless
you\'ve got a direct sunlight on it, there\'s no way in hell you can see
anything. That\'s an amazing phenomenon on an airless planet. It\'s
amazing how much we count on reflected and refracted light here. But
there, unless you had it directly in sunlight, it was just pitch black.
And you couldn\'t see a damn thing. And that\'s what he was wrestling
with, there. The dirt was packed in around it and, besides that, he
couldn\'t see down in there, unless we picked it up, physically, and
twisted it and held it so we could get it in the sunlight. He couldn\'t
see what he was doing.\"\]*

*\[Mitchell - \"And the little screw on the Boyd bolt - the release -
was probably a quarter of an inch (0.6 cm) or less.\"\]*

*\[In the 1971 Technical Debrief, the crew suggested that, if it could
be done without jeopardizing the integrity of the package during the
high-vibration of launch, it would be a good idea to eliminate the Boyd
bolt that was relatively inaccessible.\]*

**UPSUN AND DOWNSUN**

*\[Shepard, from the 1971 Technical Debrief - \"One comment about
lighting that\'s pretty much the same as everybody else has said. There
are, obviously, two areas where it\'s difficult to see on the surface.
One is looking directly into the Sun (up-Sun), and the other is looking
directly down-Sun. The only time it becomes a problem is in trying to
read the quantity of oxygen remaining, for example, on the RCU. If
you\'re (facing) down-Sun, the shadow is such that there\'s no way you
can see that needle. You\'ve got to turn cross-Sun to pick it up. With
respect to looking up-Sun, I noticed that, as we were progressing in our
traverse up to Cone (Crater), we were going just about into the Sun; and
the geologic features and differences in craters, surface textures, and
so forth were harder to notice - harder to pick up looking directly into
the Sun. If we had known this ahead of time and, consequently, had
planned to do most of our observing of craters looking down-Sun, and had
we gotten up to the top of Cone, we would have done it the same way.
It\'s just something that everybody should realize. Those are the two
places (means \"directions\") where you can\'t see very well - directly
into the Sun and directly down-Sun. Of course, once you realize that, I
think you can adapt to it fairly quickly.\"\]*

**MORTOR FIRINGS**

*\[At 3+20 in their checklists,
[Al](http://www.hq.nasa.gov/office/pao/History/alsj/a14/a14cdr-cuf1-15.gif)
and
[Ed](http://www.hq.nasa.gov/office/pao/History/alsj/a14/a14lmp-cuf1-13.gif)
planned to conduct a 20-minute geology traverse before activating the
Mortar Pack and returning to the LM.\]*

*\[Mitchell - \"Eventually, they decided not to fire the mortars. They
were afraid it would blow over the Central Station. But I\'m surprised
we didn\'t fire them before we shut the station down (along with all of
the others in September 1977).\"\]*

Note that, until Al and Ed get back to the LM, the TV picture shows an
unchanging scene - except for very minor changes in shadow length **as
the Sun rises 0.55 degrees per hour**.)

SUNANGLES CAN BE DECEIVING

**133:00:53** Mitchell: (Breathing heavily, again) The small rocks and
smaller, fresher craters, as well. Well, wait a minute, maybe I\'m being
deceived. With this slope, the Sun angle is entirely different than it
is on the flat land. The craters look sharper in these shadows.

**133:01:13** Shepard: Okay. Let\'s make an EMU stop.

**133:01:20** Mitchell: Okay. Let me pull a while

**133:01:21** Shepard: I\'d like to stop and rest here for a minute, Ed.

**133:01:24** Mitchell: Okay. (Pause)

**133:02:00** Mitchell: I thought we were in a low spot with the LM, but
it turns out we\'re really not in the lowest spot around, I don\'t
think.

**133:02:09** Shepard: Well, I don\'t know. I\'d say it\'s probably the
lowest spot right\...

**133:02:12** Mitchell: Oh, right in that particular local area.

**133:02:14** Shepard: Right there; yeah.

**133:02:15** Mitchell: But that\'s the lowest spot over to the right
(north) that I was talking about. And there\'s a low spot\...

**133:02:21** Shepard: Well, there\'s a crater over there, it\'s
true\...

**133:02:22** Mitchell: Yeah.

**133:02:23** Shepard: Yeah. (Pause)

**133:02:28** Mitchell: Doggone it, you can sure be deceived by slopes
here. The Sun angle is very deceiving.

**133:02:30** Shepard: Yep.

*RETURNING FROM CONE CRATER (HEADING DOWN SUN)*

**134:03:07** Mitchell: One of the problems of going down hill here is
that you have essentially diffraction, I guess, around your body, and it
creates a halo effect in your shadow, and you just can\'t see a darn
thing right in front of you.

*\[Jones - \"Is there an example of the halo effect in one of the
pictures?\"\]*

*\[Mitchell - \"Yeah, I think you can almost see it in the pictures.
Most shadows are absolutely black and white, but when you\'re looking
down-Sun, it\'s like it blossoms, just like it blossoms on the TV.
Around the image. When you\'re looking down-Sun, everything seems to
blossom around the shadow, right out in front of you. Around your own
shadow. It\'s like you\'re getting a diffraction pattern - a
reflection - in some way. Like the light\'s bending. It gives you a
screwy effect, it really screws up your vision.\"\]*

*\[Jones - \"That plus the zero-phase reflections that tend to wash
things out.\"\]*

**134:03:31** Haise: That\'s okay, Ed,\...

**134:03:32** Mitchell: It\'s either blacked out or washed out right
immediately down-Sun of you. We\'re going predominantly down-Sun now.
(Long Pause)