During 2009, one of us (VP) got interested in precise
photogrammetry of Apollo photos; and, through several Russian
forums, got an opportunity to collaborate with a person nicknamed
"N.A.", who was using photogrammetric software ImageModeler
to identify and locate several boulders visible in the direction
of West Crater in the Apollo 11 surface photography. Although, ImageModeler is
intended for architectural purposes, but it is useful for photogrammetry
of the Apollo images. It has a few drawbacks. For example, it sometimes has
trouble with photos containing only benchmark points distributed
on a relatively planar surface - such as parts of the lunar
surface - a problem that can be remedied by the introduction of
virtual benchmarks a few meters above the surface. ImageModeler also can become stubborn or even
unstable when the number of features in the scene under
construction gets large. Nonetheless, ImageModeler
is excellent software for obtaining good quantitative results in a
simple way.
While taking a panorama, the astronaut took one frame and then
turned about 30 degrees before taking the next frame. Except
for the special case of Pan 5, all the pans were taken in
clockwise order, with the astronaut turning to his right between
frames.
On a relatively level surface, the astronaut is able to turn
without moving much off one spot on the ground. If we could see
the pattern of footprints made while the pan was taken, it would
be a tight pattern. However, because both Neil and Buzz took
their pans with the Hasselblad out in front of the RCU - Neil with
the camera on the RCU bracket and Buzz holding his camera out in
front - camera stations (identical to the center of the film
plane) will be on a circle 0.5 to 1.0 meters in diameter around
the footprint pattern. Among other things, the outward
displacement of the film plane from the turn axis will generally
produce some stereo separation between sequential frames.
Remapped images generated with panorama-stitching software Hugin
give an impression of the direction and amount of the stereo
separation and, as well, can indicate cases in which the astronaut
moved forward or back between frames.
Pan 5 was taken in a very different manner. Neil wanted to
get a portrait of Little West Crater and was in a hurry. He
took one photo, moved about a meter east and took three more,
turning to his left between them, and then moved another meter
east and took two more, turning to his left between them. He
then moved west and took two final frames toward the west, turning
left between them. Two pairs of images give excellent
stereo.
2.1.1 Pan 1
Pan 1 camera-station map,
with the location of the
MESA-mounted TV camera marked (x). Times when
Neil turned to his right between frames are discussed in the
text.
(Click on the image for a
larger version.)
Neil took this pan just west of the ladder. Pan 1 is the
only one of the five pans for which we have a TV record.
The
Apollo 11 EVA video was digitally restored in
2009, which gives us good detail of Neil's
movements. Colin Mackellar has produced a 2 min 31 second
video clip (
14 Mb ) which starts at about
109:30:49, four seconds before Neil tells
Houston, "I'll step out and take some of my first pictures
here." Neil begins by adjusting the f-stop and/or focus on
the Hasselblad, then takes up-Sun photo AS11-40-
5850. He makes the first turn to his
right 49 seconds after the start of the video clip and then,
five seconds later, sidesteps a little farther from the
MESA-mounted TV camera. This sidestep may explain the
relatively large WSW displacement between the 5850 and 5851
stations. In a
table of camera station locations, the 5850
station is the outlier, with a distance from the central point
(0.91 m) being close to two standard deviations ( 2 x 0.18 m)
greater than the average distance (0.57 m). Neil's
subsequent turns are at 1:08, 1:22, 1:32, 1:36, 1:50, 1:55,
1:59. Because this was Neil's first lunar panorama, he may
have taken his time while he was taking the first few
frames. The interval between the first turn/step and the
next turn is 14 seconds. The next two intervals are 14 and
10 seconds. With one exception, subsequent intervals
between turns are 4-5 seconds, perhaps indicating that Neil had
gained confidence that he could turn between frames without
trouble. The exception is the 14-second interval during
which Neil took 5855. As indicated on a
decal on the top of flown Magazine S,
photographed at the National Air and Space Museum in 2006 by
Ulrich Lotzmann, Neil planned to change the f-stop setting from
5.6 to 8 or 11 when taking down-Sun photos. In the video, it
appears that, in preparation for taking 5855, he increases
the setting at about 1:39, takes 5855 at about 1:44, and
goes back to 5.6 after 5855 at 1:45. The unprocessed scans
are available on the
LPI website.
On the first lunar pan, Neil got significant overlap only
in the sequence 5885-88. These four images have been
combined as a
mini-pan.
A side-by-side comparison of the remapped images generated by
panorama-stitching program Hugin has been made by horizontally
aligning a horizon feature near the center of the overlap region
for each pair of images. In each pair, a vertical white line is
drawn downward near the center of the overlap region in the
lefthand image. A horizontal white line is then drawn low
in the left hand image. In the righthand image, yellow
traces of the white lines are drawn from rock-to-rock,
shadow-to-shadow. An analgyph made from a pair is
displayed between the two images. For these three pairs of
images, the yellow traces of the vertical lines slope down to
the left, indicating that, as expected, the camera station for
the righthand image is to the right of the camera station
corresponding to the lefthand image. Terrain, particuarly
relatively large craters, can produce local distortions of the
yellow trace of the vertical white line. In lower part of
each righthand image, upward displacment of the yellow traces of
the horizontal white line in the lefthand image would indicate
that Neil moved back between a pair of frames. Downward
displacement would indicate that he moved forward.
Side-by-side comparisons of images 5855-58,
indicating that,
as Neil turned to his right between frames, the center of
the film plane
also moved to the right. In these three pairs, Neil
got enough overlap to
provided unintended stereo. An anaglyph is displayed between
each pair.
Note the effect on the vertical yellow line of the crater on
the left in 5858.
Comparison of the horizontal white and yellow lines indicate
that
Neil did not moved noticeably forward or back during this
sequence.
(Click on the image for a
larger version.)
2.1.2 Pan 2
Pan 2 camera station
map. The distribution of stations is elongated
roughly along the trend of the raised crater rim, indicating
that Buzz
was careful where he stood. The rim of the western component
of Double Crater is drawn at the outer edge of the
relatively
steep inner wall. (Click on the image for a larger
version.)
Buzz took this pan near the
southern edge of the LM shadow about 10 meters from the
pluz-Z footpad. During the post-flight
Technical Crew Debriefing, he said that
he took the pan with the camera handheld. In the next
figure, the camera stations are plotted on a detail from the
22 December 2009 LROC image. This part of Double
Crater has a raised rim, as can be seen in a
mini-pan
assembled from three frames from Neil's ladder pan, AS11-40-
5852-54. The footprints he made
while taking the pan can be seen in oblique views provided
by various frames he took out his window after the
EVA. An example is a
detail from
A11-37-5488, which is shown along with the camera
station map with scaled bootprints added. The sole of
the boot is 33 cm long by 15 cm at its widest, so a 3 x 3
array of bootprints would cover a rectancular area about 1.0
by 0.5 meters on a side. Other than the elongation of
the overall pattern, there are no outliers in the
distribution of stations. Details are listed in
the
table of camera station locations.
Superposition of the Pan 2
map on a deconvolved detail of LROC image M116161085R
provided by GoneToPlaid. The
LROC image was taken on 22 December 2009 with the
Sun low in the east.
This image emphasizes the break in slope at the top of the
inner,
eastern wall of the
crater. The elongation of the pattern of camera
stations along
the crater rim suggests that
Buzz was careful about where he stood.
(Click on the image for a
larger version.)
The 22 December 2009 LROC image
was taken with the Sun 8.2 degrees above the eastern horizon and
shows the eastern half of the crater filled with shadow.
Pre-EVA
(AS11-39-5756) and post-EVA (AS11-37-5501) photos taken
out Neil's window show the crater with the Sun 10.9 and 15.1
degrees above the horizon, respectively. In the pre-EVA
photo, some of the inner, eastern wall of the crater in in the
shadow whereas, in the post-EVA photos taken 8 hours later show
very little shadowing, These images suggest that the inner
slope at the eastern end of the crater is 10 to 15 degrees.
There are two sequence of frames showing adequate stereo
separation: 5882a-5884 (
mini-pan including 5885) and 5888-90 (
mini pan).
Side-by-side comparison of
frames 5882a to 5884, showing the view from northwest to
north.
Although the camera staion
map suggests that Buzz took 5883 forward of both
the 5882a and 5884 locations,
comparison of the horizontal white and yellow lines within
each pair do not support that
conclusion. The indicated relative error of the
photogrammetrically-determined
5883 location is about 1 meter. As expected, both
vertical yellow lines slope
downward to the left. (Click on the image for a larger
version.)
The 5883 station position may contain error of ~0.5 m due to a
slightly-wrong focusing distance set at the time of its addition
to the IM scene model. IM refuses to accept a correction.
Side-by-side comparison of
5888-90 showing the eastern component of Double Crater
and part of the western
component. The yellow horizontal line in 5889 is lower
than its
white counterpart in 5888,
indicating that Buzz moved a bit forward between the two
frames.
Note the signficant effect of
the craters on the shapes of the vertical yellow lines.
(Click on the image for a
larger version.)
2.1.3 Pan 3
Pan 3 Camera Station
Map. Buzz took this pan about 8 meters north of
the plus-Y footpad, on the rim of an 8-m crater. A labeled detail
from the
22 December 2009 LROC image shows the camera station
location relative
to the crater.
(Click on the image for a larger version.)
As can be seen
in a
detail from
Neil's Pan 4 photo
AS11-40-5932, the Pan 3 crater does not have
a raised rim, so Buzz did not have to be quite as careful with
his footing as he was when taking Pan 2. As was the case
with Pan 1, the stations well ordered around the mean-distance
circle, The exceptions are AS11-40-5915 and 5916.
Both show parts of the LM, so the station locations are well
determined. In 5916 we see the back of Neil's PLSS. Neil
is just to Buzz's left a a bit closer to the LM and is using the
Apollo Close-up Stereo Camera. What may have happened is that,
after Buzz took 5915, he realized he would have to go around
Neil on the north side and get far enough west to finish the
pan. Neil may have backed in the field-of-view just as
Buzz was taking 5916. Another factor may have been a
fist-sized rock on the south edge of the mean-distance
circle. Details from the best photos we have of this rock
-
AS11-40-5858,
taken as part of Pan 1; and
5929 and
5932, taken as part of Pan 4 - suggest that
it sits on the southwestern rim of a small, fresh crater.
The rock and fresh crater may have contributed to Buzz's
decision to move around them on the north side. In 5932,
note the patch of undisturbed soil east of the rock, which is
another indication that Buzz moved from the 5915 station to the
5916 station on the north side of the rock.
Side-by-side comparions for 5907-11 (mini pan),
covering the Pan 3 crater, labeled "α"
in the camera station
map. The crater isn't very deep, so it doesn't have as
large an
effect on the vertical yellow traces as Double Crater did in
the Pan 2 comparisons.
The photogrammetric map
indicates that Buzz moved back between 5908 and 5809, and
then forward again before
taking 5910. The side-by-side comparisons do not
support that
result. The implied position error is about 0.5 m.
(Click on the image for a larger version.)
2.1.4 Pan 4
Pan 4 Camera Station
Map. Neil took this pan about 17 meters
from the SEQ Bay on an
azimuth about 30 degrees south of east.
(Click on the image for a
larger version.)
Neil took this pan after taking
a few photos of Buzz offloading the EASEP packages. As
can be seen in a
comparison,
the five camera stations (5930, 31, 32, 40, and 41) for
photos showing parts of the LM or boulders which would have
been visible in photos taken from near the LM are well
ordered along the circumference of the mean-distance
circle. The other 7 camera stations in the pan are not
well ordered. As detailed in the
table of
camera station locations, the mean distance of the 12
stations from the central point is 0.428 meters, with a
standard deviation of 0.272 meters. The five stations
on the west side of the pan have a mean distance of 0.310
meters and a standard deviation of 0.054 meters. The
remaining seven stations have a mean distance of 0.461
meters and a standard deviation of 0.305 meters. Neil
demonstrated while taking Pan 1 that he was able to turn in
a systematic way without trouble, suggesting that the
distribution differences between the two groups of Pan 4
camera stations is due unavoidable photogrammetric
uncertainties when only boulders well away from the LM are
available for use as benchmarks.
Note that the largest displacement of a camera station from
its expected position on the violet circle is about 1.0 m,
in the case of 5934.
With the exception of the up-Sun images, 5936 and 37, Neil
got enough overlap between adjacent frames for assembly of a
nearly complete panorama (
5.7 Mb). Side-by-side comparisons
of the remaining frames demonstrate that Neil took the pan
much as he did Pan 1, turning on about the same spot with
little motion forward or back between frames.
Side-by-side comparisons of frames 5930 to
34. In the photogrammetric analysis,
the 5933 and 5934 camera
stations are not part of a well-ordered sequence
comparable
to those of Pan 1 and Pan
3. The side-by-side comparisons demonstrate that
Pan 4 was,
indeed, taken in a very
orderly fashion and, that, as expected, the scatter in
the
photogrammetrically-determined
loctions
is due to the availability of only distant
boulders for doing
triangulation. (Click on the image for a larger
version.)
Side-by-side comparisons for
frames 5937 to 41, plus 5930. This sequence
tells the same story: Neil
took a well ordered pan. Note that Neil actually took
5941 from a spot to the right
of 5930. To make a comparison with 5930 attached
to the end of the
sequence, the white lines were drawn in 5930 and the
yellow
traces on 5941. Because
of Neil's shadow, two vertical lines were used. Note
that the vertical displacements of the horizontal lines in
5930 and 5941 indicate
that Neil ended the pan a very short distance back from where he started.
(Click on the image for a larger version.)
2.1.5
Pan 5
The Pan 5 station locations calculated in the full, 116-station
photogrammetric analysis had some obvious discrepancies,
particularly with regard to their locations relative to the
prominent 4.5-meter crater just a few meters north of the spot
where Neil took the pan. These discrepancies were due to
(1) technical issues in using IM when the number of benchmarks
is large; and (2) the fact that the only benchmarks visible in
photos 5954-59 were distant boulders.
To remove these discrepancies, we performed a three-step process
to determine the correction ocations of the stations:
(1) We did a dedicated
photogrammetric analysis for 5954-5959 using about fifty local
rocks as benchmarks. A
labeled detail from the
assembled pan
and a
plan view
show a set of fifteen of these rocks. The analysis
demonstrated that the relative positions and azimuths of
frames 5954 and 5956-59 differed only slightly from those
found in the full, 116-station photogrammetric analysis.
The differences are well within the range of expected errors
and are not shown. The local analysis also showed that,
although the azimuth calculated for 5955 was virtually the
same as in the 166-station anaylsis, the station location was
virtually identical to that of 5957, instead of being about 2
meters NNE of 5957. As discussed below, detailed
intercomparisons of the 5955-5957 images confirm that the the
three were taken about the same spot.
(2) The local photogrammetric analysis is not directly tied
back to images of the LM and, therefore, only gives relative
locations of the six stations. However, Neil took Pan 5
near a sharp-rimmed, fresh crater just inside the southwest
rim of Little West Crater. Consequently, we included in
the local analysis ten small rocks on or near the rim of the
4.5-m crater. The photogrammetric locations of these ten
small rocks was then fit with a circle. The pattern -
circle and stations - was then scaled so the radius of the
circle matched the 4.5-m radius of the small crater and was
then shifted to place the circle over the crater rim.
(3) As a final step, stations 5960 and 61 were moved in tandem
along a line defined by the 5961 central azimuth until the
azimuth from 5960 to the true position of boulder j2 agreed
with the value of 15 degrees to the right of the 5960 central
azimuth derived from the 5960 image. The two stations
were moved 0.9 meters toward the other Pan 5 stations.
A graphic presentation of the three steps follows.
Animation showing the
three-steps process used to place the Pan 5 stations at
their
proper positions near the 4.5-m crater just inside the
southwest rim of Little
West Crater. Note that the red dot near the top left
in the figure indicates
the actual position of boulder j2, with the sunlit face on the
right (east)
and the shadow on the left. (Click on the image for a
larger version.
2.1.5.1 Camera Stations
5954-59
As indicated in the map above, Neil began Pan 5 with
5954, taken about 1.5 meters WSW of the ALSCC. He then
moved about a meter southeast and took a set of three frames,
starting with 5955 which shows a view aimed a bit more
easterly than 5954, and then turned to his left to take 5956,
and left again for 5957. Neil then moved about a meter
ENE and took 5958 and 59, turning left between frames.
He finished the sequence by moving to a spot beyond the
ALSCC to take 5960, which shows the TV and other benchmarks
north of the LM, and 5961, which is aimed at the LM.
In the following, a series of side-by-side comparisons confirm
the relative locations of frames 5954 to 5959. We begin
with two pairs - 5956-57 and 5958-59 - with excellent stereo
separation.
Side-by-side comparison of AS11-40-5957 (left) and 5956
(right).
As shown in the photogrammetric map, 5957 was taken
slightly to the left of 5956.
This is confirmed by the fact that the yellow trace in
5956 of the vertical white line
slopes down to the left. In addition, there are only
very small vertical differences in the
intersections of the horizontal yellow lines with the
vertical yellow line compared with
their white counterparts. This indicates that the
two camera stations have no
appreciable forward or backward position difference.
(Click on the image for
a larger version; and click here for a full version of the
anaglyph.)
While the side-by-side
comparison of 5957 and 56 confirms the relative locations of
the two camera stations, the anaglyph made from the two images
shows two major breaks in slope which conceal portions of the
crater floor beyond each of them. These breaks in slope
are on the right in 5957 and across most of the image in
5956.
Comparison of details showing
breaks in slope in 5957 (top)
and 5956 (bottom). The dashed red-lines approximate
breaks in slope. (Click on the image for a larger
version.)
The breaks
in slope can be located by three techniques. First, at
some places there is a discernable change in image clarity
across the breaks The images were taken at 74-foot
focus, so the surface on the near side of a break in slope
will be more out-of-focus than the surface beyond. Second,
patterns of rocks and shadow on one side or the other of a
break in one of the images can be identified at the same
relative location in the other image. However, a
pattern across a break in one frame will have a lateral
discontinuity in the other frame. For example, in 5956
a pattern beyond a break in slope will be displaced to the
the right compared to its location in 5957. And third, rocks
and shadows that are visible in one frame of a pair may not
be visible in the other if the latter was taken behind the
first.
One other pair of frames, 5958 and 5959, form an excellent
stereopair. A
side-by-side comparison confirms the
relative placement of the camera stations in the
photogrammetric map, with 5959 having been taken just to the
right of 5958 and with no signficant forward/backward
displacement.
Click here for a full resolution version of
the anaglyph.
The photogrammetric map indicates that 5958/59 were taken to
the right and forward of 5957/56. Image 5956 has no
overlap with either 5958 or 59, except right at Neil's
feet. Image 5957 has a useful amount of overlap with
both 5958 and 59.
Side-by-side comparisons of
5957 (center) with both 5958 (right) and 5959 (left).
The white vertical and
horizontal lines in 5957 are traced in yellow on each of the
other images. (Click on
the image for a larger version.)
The side-by-side comparisons
between 5957 and both 5958 and 5959 show, not surpisingly,
nearly identical yellow traces of the vertical line,
indicating nearly identical displacement of 5958/59 to the
right of 5957. The fact that the yellow traces of the
foreground horizontal line both slope down to the right is
another indication that the 5958/59 stations are to the right
of 5957. Both stations are also forward from 5957, as
can be seen by the fact that the intersections of the
foreground yellow traces with the vertical yellow traces are
lower (farther from the horizon) than the corresponding
intersection in 5957. The forward displacement is large
enough to preclude good stereo of the foreground.
Comparison of details of 5957
and 5958 showing the 4.5-m crater.
The dashed portions of the
yellow traces indicate parts of the surface
that are visible in 5958 but
are hidden in 5957 by the crater rim. This is
a clear indication that
5958/59 were taken forward of 5957. (Click on
the image for a larger
version.)
The special photogrammetric
analysis done for 5954-59 shows that the 5955-57 stations are
tightly bunched. We have seen that 5957 was taken a
short distance to the right of 5956, with enough separation to
give good stereo. A comparison between 5955 and 56 (next
below) shows that the intersections between the yellow traces
in 5955 are slightly above the corresponding intersections in
5956, indicating that 5955 was taken slightly behind 5956.
Side-by side comparison
between 5956 (left) and 5955 (right).
(Click on the image for a
larger version.)
In addition, portions of rocks
visible in 5956 are hidden in 5955. A
detail
showing the break in slope that hides part of the central
mound in both images clearly shows that more of the central
mound is visible above the break in slope in 5956 than in
5957. A second
detail, covering the break in slope nearest
Neil, shows similar differences. The fact that the
yellow trace in 5955 of the vertical white line is very close
to vertical indicates that the 5955 station is virtually on
the backward extension of the 5956 aiming azimuth.
The photogrammetric map shows
5954 and 5956 where aimed in the same direction, with 5956/7
having been taken about a meter to the right. It appears
that 5956 may have been taken a short distance farther into
the scene than 5954.
Side-by-side comparison of
5954 (left) and 5956 (right).
(Click on the image for a
larger version.)
The fact that the horizontal
yellow traces slope down to the right and the vertical yellow
traces slopes down to the left confirm that 5956 was taken to
the right. In addition, the yellow interestions are
below the white intersections, indicating that 5956 was taken
forward (in the northeast direction) of 5954.
2.1.5.2 Camera Stations
5960-61
Side-by-side comparison of
5961, 60, 59. Stereo information available from the
image pairs
is strongly influenced by
relative displacement of the camera stations along the
azimuths
defined by the centers of
the overlap regions.
The center-line azimuth of the 5961/60 overlap
is roughly 15 degree north
of west; and the center-line azimuth of the 5960 overlap
is roughly
40 degrees north of
west. The anaglyphs have been rotated left so that the red
and blue images
of prominent features line up
horizontally. In each case, a rotation of 45 degrees
gives
reasonable stereo. (Click on the image for
a larger version.)
Of the final two images,
5961 shows the LM and various benchmarks near it,
while 5960 shows the TV camera near the left edge.
As indicated by the
slight leftward slope of the vertical yellow trace in 5960
(above), 5961 was taken slightly to the left of 5960.
The upward displacement of the horizontal yellow traces in
5960 indicate that 5961 was taken a short distance farther
into the scene than 5960. The leftward slope of the vertical yellow
trace in 5959 indicates that 5960 was taken to the left of
5959. The leftward displacement of 5960 from 5959 is
significantly great than the leftward displacement of 5961
from 5960. Similarly, the upward displacements of the
horizontal yellow traces in 5959 indicates that both 5960
and 5961 were taken much farther into the scene than 5959.
2.1.5.3
Location of Pan 5
As mentioned previously, the small-scale photogrammetric
analysis focused on Pan 5 included a number of small rocks on
the rim and inside the 4.5-m crater. These have been
used to properly place Pan 5
relative to the 114-image photogrammetric map.
Locations were determined for ten small rocks on the rim
of the 4.5-m crater. A mean radius was calculated to serve as
a length scale for appropriately sizing the small-scale
photogrammetric map. Then, using locations of rocks on
the rim and inside the crater, a best overlay on the 22
December 2009 LROC image was determined.
New Pan 5 camera stations
superimposed on the 22 December 2009 LROC image,
using a mean circle derived
from ten points on the crater rim to get proper scaling
and location.
An
animation
compares the old locations of the Pan 5 stations with the
new locations under high-Sun conditions. With the Sun nearly
overhead, Neil's path out from the EASEP site shows up very
well. It is pleasing that the new analysis puts Pan 5
at the end of the Neil's track.
To summarize, comparisons between pairs of Pan 5 images that
have some overlap demonstrate that the apparently
haphazardous distribution of camera stations is actually a
reasonable representation of how Neil took this set of
photographs. Specifically, Neil took 5954 near the
ALSCC, then moved a meter east, perhaps to get farther away
from the ALSCC. He took 5955, turned slightly to his
left - moving forward a bit in the process, took 5956, and
then turned left again to take 5957. Next, he moved
about a meter farther east and took 5958 and 5959, turning
slightly to his left between the frames. Finally, he
moved toward the ALSCC, took 5960, aiming a bit north
of the LM, and finished off with a shot of the LM, 5961.
2.2 Comments
on images and camera stations
General comments: Figure
3-15 in the
Apollo
11
Preliminary Science Report (hereafter, the Preliminary map)
is in good general agreement with the new photogrammetric results.
Most differences between the two maps are within the ranges of
uncertainty estimated by Batson and Larson Notable
exceptions include (1) tilt angles of many stations shown in
the Preliminary map are estimated erroneously; (2) some camera
stations are misplaced, such as 5892, 5921, and 5967-70; (3)
azimuths are sometimes wrong, as with 5942-44; (4) distances from
LM to the PSEP and associated camera stations are underestimated;
and (5) individual stations within each panoramas were not
determined by Batson and Larson.
5851: This is one of a few photos in Pan 1 and
Pan 2 that include in the field-of-view a very old, eroded
~22-meter crater just next to the Double Crater on the southeast.
This crater is visible in LROC images - such as a
labeled
detail from 22 December 2009 - but its presence is difficult
to pick out in EVA photos. This crater is between the foreground
and the ~6-m
ι crater (seen just in front). Boulders
l1
and
l2,
which are identifiable on LROC images, are near the horizon to the
left from the center, boulder
a is to the right from the
center, the top of boulder
s seen just below
a to
its left.
5855-56: A sharp, fresh crater is seen on the righthand edge of
5855 and at the center of
5856. Photogrammetric analysis confirms
that this is the crater identified in a
detail from the 22
December 2009 LROC image. The crater is about 70 meters from
the LM. See, also, a
labeled version of a pan Buzz took out his
window after the EVA and a similarly-labeled
animation made from
nine LROC images of the site.
5858-59: The new locations show that Neil
moved about 3.8 meters north from the Pan 1 location before he
took 5859.
5859-61:
In
a map detail, the three camera stations
marked with red dots. These indicate that Neil
moved slightly to his left after taking the first of the three
frames, then farther left and forward after the second. A
side-by-side comparison of 5860 and 61 shows that there is no
significant forward or backward separation between the two.
5859 has significant motion blurring; 5860 is better; but 5861 is
the only one of the three what is reasonably sharp.
5862-63: These two images of Buzz
crawling out of the camera were not shown in the Preliminary map.
5863-65: A tight cluster of
stations, less than 0.5 m from each other.
5866: The bright boulder visible above
the MESA and beyond the inside edge of the north strut can also be
seen in
5903, the well-known, full-length portrait of
Buzz.
5867-69: All three photos made from
nearly the same place, with only slight azimuth and tilt changes.
Made from the rim of the older, eastern component of Double
Crater.
5871: During early stages of the
photogrammetric analysis, the 5871 station location depended
primarily on distant boulders. During September 2010, a
number of very small pieces of rock were added to the benchmark
pool so that station locations could be determined for 5865 and
other close-up photos. One of us (VP) realized that some of
these small rocks were in the 5871 field-of-view. Forcing IM
to accept these new benchmarks in re-positioning 5871 required
painstaking work and about 40 recalibrations. The net result
is that the 5871 camera station shifted about 0.5 meters to its
present location. This exercise provides an
order-of-magnitude estimate of the uncertainties in station
location dependent solely on distant boulders.
5872-73: The azimuthal difference between these
two photos is less than 2 degrees, with Neil moving forward along
that line between the frames. West Crater is near the
horizon on the lefthand side of 5872 (
detail) and can
also be seen in 5873. The landscape is so flat that it is
difficult to estimate distances. As can be seen in a
labeled detail from
the 22 July LROC image, the southern portion of Little West Crater
lies in the same direction as the portion of West Crater visible
in these two images. A
detail from 5872 may show Little West, as
labeled. The southern portion of Little West is hiding the
lower parts of various boulders located between the two
crater. See, also, a discussion in section 3.4 of a shadowed
wall inside the east rim of an old, heavily-eroded crater
immediately southwest of West Crater.
5874-75: Several boulders identifiable on LROC
images are present. The largest is boulder
a.
5876-80: These Boot Penetration Soil
Experiment photos are not included individually in the camera
station map because determining the locations would be a very
tricky photogrammetric task. However, their positions
and azimuths are found approximately from photos where BPSE area
is clearly visible:
5884/85,
5905, various post-EVA window photos, and the
16-mm film shot out Buzz's window.
5881-91: Panorama 2 made from the rim of the
younger and sharper, western component of Double Crater.
5883: The station position may contain an error
of ~0.5 m due to a slightly-wrong focusing distance set during
modeling. Correction of this error would be tricky. Actual
location is to the south of the location on the map, so the actual
location is closer to the panorama central point.
5888: In a
labeled detail, the old eroded crater mentioned
in the comment for 5851 (above) is in the center just next
to the eastern rim of Double Crater. Left portion of
t-group
of LROC boulders are to the left near the horizon (where the
southern portion of the rim of West crater is seen),
l1 and
l2
are near the horizon to the right.
5892/93: 5892 was wrongly placed in the
Preliminary map. It was shot in front of Quad I, not Quad II. In
fact, 5892 and 5893 were shot from essentially the same location
(calculated horizontal separation ~16 cm) and at similar azimuths
(difference ~13.6 deg). It appears that, having positioned the
camera to shoot under the LM in 5892, Buzz immediately
repositioned himself slightly, tilted his camera up by ~45 deg and
took 5893, showing the Ascent Stage. It's interesting that there
are no common details in 5892 and 93, so the camera locations were
calculated photogrammetrically completely different sets of
benchmarks. However, photogrammetry reveals that the locations are
nearly coincident. This pair may serve as an indirect
demonstration of the accuracy of the model: such close coincidence
of two consecutive camera locations cannot be accidental.
5894: Photogrammetric position less than 0.5 m
from 5892/93.
5897/98/99: Not present in the Preliminary
map. These three photos of the plaque have nearly identical
station locations, virtually over the center of the plus-Z
footpad. 5897 and 98 are separated by about 2 cm, while 5899
is about 8 cm from both. Inclination, azimuthal, and
rotational differences are small. The three inclinations are
30.3, 30.1, and 28.7 degrees
below horizontal, respectively. Neil can be seen
taking these photos in clip from the 2009 restoration of the video
linked at
110:41:07. Neil took them with the camera
handheld far enough forward that it was over the center of the
footpad
.
5900: Not present in the Preliminary map.
This final plaque photo was taken from a location about 0.8 m
northwest of the center of the plus-Z footpad. The camera
inclination is only 13 degrees below horizontal.
5901/02: These two photo were taken from
virtually the same spot. Between the frames, Neil turned to
his left, not to his right as the Preliminary map shows.
Boulders
b and
c are the largest LROC boulders visible
in these to images.
5903: Shows both
b and
c.
5904: This is the only one of the 123 EVA
photos for which a location can't be assigned. No
recognizeable features except the suit are visible.
5905/16: Panorama 3, taken from the rim of the
~8-meter crater
ι to the north of the LM.
5905: The Preliminary map shows the flag well
to the right of center and indicates that the SWC should be in the
frame. The new map and actual photo show the flag centered
and the SWC out of the frame.
5907/08: Show the "fresh" crater and boulders
in
e-group.
5909/10/11: Show LROC boulders to the
north and northeast of the LM.
5910: In the Preliminary map, the estimated
azimuth points too far left. Perhaps the authors of the
Preliminary map did not recognize the relative brightness of the
Sun-facing inner wall of the
α crater.
5912: Camera tilt ~14 below the horizon.
5915/16: Buzz moved more than 1.6 m to
his right between the frames, probably trying to avoid Neil, who
was moving toward him from the right, carry the ALSCC.
Despite Buzz's efforts, Neil's back appears in 5916.
5917/18/19: The tilts of 5917 and 5919
were overestimate in the Preliminary map. Buzz appears to
have taken these three along a line, stepping to his left about 1
meter between the frames.
5920/21: The Preliminary map shows 5921, which
is view under the LM of the descent engine bell, as having been
taken out in front of Quad IV and aimed toward the southeast. The
shadows show that it was taken out in front of Quad III, aimed
toward the southwest. It was taken only ~0.3 m north of
5920. Buzz turned to his left by ~100 deg between the shots.
5922: Not shown in the Preliminary
map. Azimuth very close to that of 5921.
5923/24: Not shown in the Preliminary
map.
5925/26: The new locations differ from those in
the Preliminary map only by centimeters. The tilt of 5926
was underestimated in the Preliminary map.
5927/28/29: Contrary to what is shown in
the Preliminary map, these three images were shot from the same
location, all within ~10 cm of each other.
5930-41: Panorama 4 was made near the
northern rim of the old, eroded crater mentioned in the comments
for 5851 and 5888. This old crater is only evident in the
LROC images taken with the Sun at low elevation. Note that
the azimuths of the first (5930) and last (5941) frames differ by
only about 6 deg.
5938: The azimuth crosses the very old,
eroded crater mentioned in the comments to
5851 and
5888. Although the crater interior is in the
foreground, only the far (southern) rim can be picked out as a
slight rise that is brighter than the more distant surface and
obscures part of it. As indicated by a line of small, yellow dots
in a
detail,
the rim line passes through the row of reaseau crosses just below
the horizon. The rim line hides the lower part of the boulder
a.
5942/43/44: In the old map, these camera
locations are closer to the LM and direction arrows point more
toward the east than in the new map. The new positions and
orientations are much more consistent to the location of the
crater Buzz is passing and the locations of the stones beyond
it. The Preliminary map indicates that Neil turned to his
right between frames. He actually turned left.
5945: Azimuth very close to that of 5942.
5946/47: Taking from the same location
with the same azimuth. Camera tilted up for the second
image.
5948: The PSEP is actually to the left of
center on 5948, not to the right as on the old map. Also, the
small stones shown around the PSEP and LRRR on the Preliminary map
are difficult to identify in the photos.
5949/50: Taken at the same location but with
different azimuths and tilt.
5951: Not surprisingly, the location on
the Preliminary map relative to the PSEP is very accurate.
The tilt is overestimated.
5952: Taken ~3.2 m from the LRRR.
5953: Taken ~1.3 m from the center of
PSEP; ~0.4 m from the western solar panel; camera tilt ~30 degrees
below the horizon.
5954-61: Pan 5 images taken at the end of
the track Neil made running out to the southeast rim of Little
West Crater. Extensive discussion in
Section
2.1.5.
5954/55: The largest boulder in these
photos is
c,
a ~2-meter-tall boulder ~140 meters from the Pan 5 location.
Boulder c is ~315 m from the rim of West Crater, from
which is was probably ejected.
5958/59: Boulder
b, a 2.5-m, elongated rock
is near the center of these images.
5965/66: Not shown in the Preliminary
map. While standing at the MESA, Neil advanced the film by
seven frames before removing the magazine from the camera an
stowing it in the ETB. These two images show a small
vertical slice of the surface in the southeast direction,
including
ι
crater. The station locations were determined using a
selection of small rocks as benchmarks. Although the
locations could be expected to be more uncertain than 5967-70,
which show nearly full-frame views in the direction of the SWC
shaft, the positions of the two groups of camera stations are
separated by only about a meter.
5966A: This is a view into the MESA shadow and
is so underexposed that only faint details can be seen.
However, similar details can be seen in the dark areas of 5965 and
5966. We assume that 5966A was taken at virtually the same
location as 5966.
5967/70: The locations of these last four
EVA images differ significantly from the locations indicated in
the Preliminary map. Their actual locations are within 0.8 m
of 5965-66A.
Perhaps the most striking feature of the 1978 map compared with
the 1969 map is the very different distribution of craters.
The craters sketched in the 1969 map were probably derived from
the
best Lunar Orbiter image, supplemented by
photographs taken out the LM windows and on the surface.
Photogrammetric methods are not well suited to mapping crater
rims. Only small, fresh craters with raised, circular rims
can be located accurately with trigonometry provided that camera
stations are well defined. Further discussion of craters can
be found in
Section 4.
Left: The 1978
map includes the locations of the TV, U.S. flag, LRRR, and
PSEP along with trails made by the astronauts.
"ALSCC" denotes locations where the Apollo Lunar Surface
Close-up Camera can be seen in various Hasselblad
images. Right: An overlay of the 1969 and 1978 maps
indicates that, in the 1978 map, the TV and US flag are
about 2.5 and 1.3 meters, respectively, farther west
and somewhat north of the 1969 mapped locations. The
SWC at the same location in both maps; and the LRRR and
PSEP are 3.8 and 5.9 meters, respectively, farther south
in the 1978 map. (Click on the image for a larger
version.)
3.1.1 Group e boulders
During a
post-flight press conference, Neil said,
"(There were) rocks in a boulder field (that we photographed)
out Buzz's window that were 3 and 4 feet in size.
Very likely pieces of lunar bedrock. And it would
have been very interesting to go over and get some samples
of those. We have the problem of a 5-year-old boy in
a candy store. There are just too many interesting things
to do." This boulder field can be seen in 5516, below,
with labels applied to ten rocks that have been located
photogrametrically.
Frame AS11-37-5516, taken out
Buzz's window after the EVA, shows a boulder field
northwest of the LM. Note the small, fresh crater along
the line-of-sight to e9.
(Click on the image for a
larger version.)
The boulders in this group can be identified in the LROC
image taken on 22 December 2009, when the Sun was only 8.2
degrees above the eastern horizon. The boulder field
visible out Buzz's window contains far more than ten rocks. In
the window photos, many smaller pieces of stones are visible all
around; and , in the LROC image, a couple of larger stones with
distinct shadows are seen to the north and to the west of the
ten labeled boulders. However, I’m not able to recognize these
stones in any photos taken during the EVA. Window photos, by
themselves, do not give useful photogrammetric results because
of very small parallaxes provided by any pair of window photos.
Some of the larger stones visible in the LROC images but not in
the EVA photos may be hidden behind the local terrain. One
example is a rock west of boulder e2. Because small rocks
are much more numerous than large ones, few can be identified
with confidence and, consequently, are not labelled.
This portion of the 22 December
2009 LROC image contains the boulders in Group e.
In the top and bottom panels,
actual locations of the boulders are marked with green dots (●)
and, in the bottom panel, the
photogrametrially-determined locations are marked with red
dots (●).
(Click on the image for a
larger version.)
we
should check the Pan 5 location.
Although some of the Group
e boulders, such as
e1,
are visible from a variety of directions, others are only
visible in photos taken out Buzz's window and in frames
5960-61 from
pan Neil took on the rim of Little West Crater. From other
locations, they are hidden by a rise to slightly higher ground
west of the LM. Evidence of this rise can be seen in an
animation made from
two LROC images: one taken with the Sun low in the west; and the
other with the Sun low in the east. In the July 2009
image, the sloping ground west of the LM is facing away from the
Sun and is darker than other parts of the image because it is
being illuminated at a shallower angle. In the December
2009 image, the sloping ground is facing the Sun, so it's
relatively bright.
This slope to slightly higher ground west of the LM blocks the
view to many boulders which are otherwise visible only in photos
made from the window (with the camera altitude of ~5.3 m above
the LM footpads) and in Pan 5 photos taken from the rim of
Little West Crater, which has an altitude about the same as the
LM windows. Unfortunately, in Pan 5 photos
5960-61 the
group
e
boulders are seen from a far distance, and are near the
horizon. In addition, 5960 is badly blurred. These factors
make identifications difficult. In addition, the combination of
the two positions - Pan 5 and the Buzz's LM window - provide
only a small parallax. Fortunately, from the Pan 2 location on a
crater rim just south of the tip of the LM shadow, six members
of group
e are
visible
in frames 5883-84. This gives larger parallaxes.
e1:
distance ~ 92 m from the center of LM; length/height 1.5/1.5
m. This boulder is the largest in the group; its shadow is
very prominent even in the lower-resolution,
July LROC image.
e2:
distance ~ 92 m from the center of LM; length/height 1.5/1 m.
This boulder is not seen on majority of photos, except for
window shots and Pan 5. Fortunately its top is also seen from
the high point of Pan 2 (
5883/5884), this helps to improve parallax
and accuracy. This boulder is particuarly prominent in the
29 October LROC
image, taken when the Sun was east of the zenith at an
elevation of 64 degrees.
e3:
distance ~ 80 m from the center of LM; length/height 1.5/1 m.
In the Hasselblad images, this boulder is seen only in the
window shots and in Pan 5.
e4:
the eastern-most boulder in the group, sits on the rim of a
crater. As can be seen in a
detail from 5515, this is actually a group
of at least 3 boulders, one large boulder, with two smaller
ones in the foreground. Distance ~56 m from the center of LM;
length/height of the main boulder 1/0.5 m; the lesser boulders
are two times smaller. This very prominent group is seen on
many shots in the northern direction due to its high position
on the rim of the small crater. Despite its prominence, it is
barely distinguishable even on high-resolution LROC photos,
obviously due to its short shadow cast onto the nearby rim
portions.
e5:
a group of at least 2 boulders side-by-side (
see a detail from
5883) on the
rim
of a depression behind the "fresh" crater. Distance ~64
m from the center of LM; length/height of the each boulder
0.5/0.5 m. The upper portions of
e5 can be seen in many
shots in the northern direction due to their position on the
rim of the
depression. In LM window shots,
e5
is directly projected onto boulders
e6 and
e7.
This gives the impression that
e6 and
e7
are assciated with e5, but they are not.
e6 and
e7: only about 3 - 4
meters apart, at virtually the same distance from the LM, and
close to the lines-of-sight from the LM to
e3
and
e5.
Distance ~71 - 72 m from the center of LM; length/height
cannot be accurately estimated since only upper portions are
seen from the window and because of the large distance from
Pan 5 location. The very top of
e6 is seen from the high
point of Pan 2 (
detail
from 5883). Not seen on other shots being obliterated by
the rim of the depression and the rim of the fresh crater.
e7
is barely seen on some of high-resolution LROC photos. In the
LM window shots, as seen in a
detail from 5516,
e6 and
e7
are partially hidden by
e5 and seem to be a part of the
same grouping. (Actually, before I got low-sun,
high-resolution LROC images, these boulders were enigmas for
me. I could not identify two boulders on 5960/61 since nothing
seemed to correspond to them on other photos. At the same time
I saw two unexplained boulders that appeared to be clustered
with the two
e5 boulders in window photos, one to the left
and one to the right of the central group. Before I had
the LROC images, I could not understand
e6 and
e7
because the two e5 boulders, being very prominent, do not have
any nearby boulders in any of the EVA photos that would
correspond to
e6 and
e7.)
e8, distance ~ 93 m from the
center of LM; length/height 1/0.5 m. Screened by the rim of
the depression and by the rim of the fresh crater, so is seen
only in window shots and on Pan 5.
e9,
the most distant in the group. Distance ~ 103 m from the
center of LM; length/height 1/0.5 m. Screened by the rim of
the depression and by the rim of the fresh crater, so is seen
only on window shots and on Pan 5.
e10,
distance ~ 93 m from the center of LM; length/height 1/0.5 m.
This relatively small boulder is situated farther east than
most members of group e,
so it is not hidden by the slope west of the LM and can be
seen in Pans 1, 2, 3, and 5 and from Buzz's window.
3.1.2 Boulder f
This boulder is 31 m from the center of the LM and only 10 m
west of the TV camera. Its size is about 0.5 m. Due to its
proximity to LM and its presence in many EVA photos (such as
5883) and from
Buzz's window photos (as in
5483), photogrammetry locates it very
accurately, with an error well less than its size. As can
be seen in an
animation, boulder
f is barely visible in
the Oct and Dec 2009 LROC images. However, it seems to be
the closest boulder to LM that may be distinguished on LROC
images, so I decided to include it in the photogrammetric
analysis. (It is interesting that several such boulders
are at the limits of visibility in the original LROC images; but
when the originals are resized with interpolation, some such
boulders become more visible. Nonetheless, if you do not
know a boulder is there, you're not able to say that it is
really a boulder and not a minor relief feature.)
3.2 Boulders Northeast of the LM
Boulders in this group primarily appear in Pan 2 and Pan 5, a
combination that gives good parallax. Of the eight boulders,
the three largest -
b,
c, and
d - are easily
visible in the lower resolution, July 2009 LROC image. Two others
of intermediate size -
j and
h - and three smaller ones
-
g,
i,
and
k
- can be picked out in LROC images taken after the spacecraft was
moved down to 50-km altitude. Some of these are seen only because
their shadows fall on ground that is sloping down, away from the
Sun. Boulders
i and
j sit on ground that slopes down
to the west; Pan 5 images, taken with the Sun low in the east,
illustrate the effect of a slope on shadow length. Visiblity of
some of the boulder, such as
k, may be enhanced in LROC images
because their top surfaces are relatively bright, particularly
when the Sun is high in the local sky. See, also, labeled
versions of
5886,
5903, and
5958.
Identified boulders northeast
of the LM as seen in Buzz's plus-Z pan (Pan 2).
The central part of the pan
assembly was made from frame 5885, in which boulder h
is hidden behind the US
flag. Frame 5886 was taken from a slightly different location
and shows boulder h. A small piece of 5886 has
been inserted in the figure at the proper location.
(Click on the image for a
larger version.)
Identified boulders northeast
of the LM as seen in Neil's Little West pan (Pan 5).
Note that the direction to
boulder e4 is indicated by a green dot (
●)
. The boulder, itself, is
hidden by the rising
ground west of the LM.
(Click on the image for a larger version.)
This portion of the 22 December
2009 LROC image contains
identified boulders northeast of the LM. In the bottom panel,
boulders visible in the raw LROC image are marked with red
dots (●) or yellow
dots (●). (Click on the
image for a larger version.)
Distances in the following descriptions were measured on
GoneToPlaid's deconvolved version of the 22 December 2009 LROC
image. Distances are given from the center of the LM and
from the point at which Pan 5 images 5960-61 were taken.
Check the latter when we have
the final 5960-61 location... or use the 5958-59 location, which
shows most of them.
Detail
from 5872 with labels applied to twelve boulders in the
general direction
of the south rim of West
Crater. Four prominent boulders assigned to the t group;
and five less-prominent
boulders assigned to the
v group. The heavily-shadowed rim of
West Crater
runs to the left from beyond
boulder t2.
Three boulders
associated with
a thin, dark line - the
inner, east wall of an old, eroded crater - are labeled "w"
and are discussed in section 3.4. (Click on the image for a larger
version.)
Up-Sun image 5887 from Pan 2,
with a small piece of 5888 added at the upper right,
showing boulders q1 - q4, t1 - t4, and v1-v5. Buzz aimed the camera low
to avoid
getting direct
sunlight in the lens. (Click on the image for a larger
version.)
All the
t-group
boulders are visible in all the Hasselblad images taken in their
direction. Because of intervening terrain, the lower parts
of some of these boulders are hidden. Regretably, none of
the Pan 5 images were aimed far enough to the southeast to include
them. They are also visible in the
first LROC image of
the site, despite the relatively low resolution of that 12
July 2009 image.
3.3.1 Boulder t1
This is the largest and most
distant of the
t-group boulders. Distance ~156 m from the
center of LM. Position estimation accuracy ~3%. Because
lines-of-sight from locations near the LM pass close to Little
West, the boulder's base is hidden by the outer parts of the
crater rim. Because Pan 2 was taken from a relative high
spot on the rim of Double Crater, more of the boulder is visible
in
5887 than in
any other Hasselblad image. From the Pan 1 location (
5850),
t1 is
completely hidden by the LM; from the Pan 3 site (
5913), only the
tip is visible; and, from the Pan 4 site (
5936) also only
the upper portion is visible in the glare of the Sun. The width
of the portion visible in
5887 is about 2 meters, with a measurement on
the Dec 2009 LROC image confirming this estimate. The portion
visible in
5887
is about 1 m. The height cannot be estimated from EVA
photos since the base of the boulder is hidden by the rim of
Little West. We see about 1 m of its upper portion on
5887. The
t1
shadow length in the
Dec 2009 LROC image is ~8 m. With the
Sun at an elevation of 8.2 degrees, the inferred height is 1.2
m.
3.3.2 Boulder t2
This is the smallest of the group and closest to the LM.
Distance ~ 108 m; accuracy ~4 %. Height/width ~1 m. In the
October 2009 LROC photo, with the Sun virtually overhead, there
is no sign of
t2 at its known location, which is at the
center of the box drawn on a
labeled detail.
3.3.3 Boulder t3
The
October
and
December
LROC images indicate that
t3 is only a bit smaller than
t1.
Distance ~124 m, accuracy ~3%. Height ~1.3 m, width ~2.3 m.
Distance from
t2 ~16 m; from
t1 ~34 m.
3.3.4 Boulder t4
t4 is about as tall as
t2,
but has enough width to be visible even in the October 2009 LROC
image. Distance ~120 m, accuracy better than 2 %. Height ~0.9 m,
width ~1.3 m. On Pan 1 (
5850) only the rightmost (south) side of the
boulder is seen, the rest being hidden by a landing gear strut.
Distance from
t3 ~8 m, from
t2 ~18 m, from
t1
~40 m.
The boulders in the
v group are less prominent in the
Hasselblad images than the
t-group boulders. Most are farther from
the LM, which means that, generally,
we are seeing only their
tips as faint, black, blurred spots sticking up over the rugae of
the terrain. On some photos they are present, on others some of
them are hidden entirely by the terrain or by the two largest
t-group
boulders:
t1
and
t3.
When combined with low parallaxes, these factors make them
difficult to distinguish in the photos. Without photogrammetry we
hardly would be able to identify most of them. Even with
photogrammetric data, I have some doubts about the identifications
and/or reality of a couple of these boulders.
Boulder groups t and v in AS11-40-5936, taken as part of Pan 4, which Neil
took while Buzz was
offloading the EASEP packages. Large parts of the t1 to t4 boulders and one of the w boulders
are visible; these are marked with red arrows. I
put red dots above the tops of boulders that are
mostly hidden, and blue dots at the
photogrammetrically-determined loactions where unseen boulders
would be if they were not screened by the terrain or
foreground boulders. I haven't included v3 in the
inset beacuse of it's separation from the others. v3 is marked with a blue dot in the
full image
because it is hidden by a group of bright, foreground
boulders; the blue arrow and dot indicates
the position of v3
behind this group, not the bright group.
(Click on the image for a
larger version.)
3.3.5 Boulder v1
Its upper portion is nicely seen
from the the rim of Double Crater rim (
5887); a smaller
portion is seen on
5872/73.
From the Pan 4 site (
5936),
I'm not sure it can be identified with confidence because of the
sun glare; on
5913
(Pan 3) it is hidden by the rim of Little West; from the Pan 1
site (
5850 )
it is hidden behind the LM. Distance ~184 m, accuracy ~3%
Distance from
t1 ~30 m.
Its size may be estimated roughly
only from the
December
2009 LROC photo. According to the size of its image and
the length of the shadow, v1 seems to be similar to
t4,
i.e. height/width is ~1 m/ 1.5 m. As seen from orbit, it is near
a small (~7 m) crater.
3.3.6 Boulder v2
v2
seems to be quite large on
December 2009 LROC images, it is also the
most distant in the group: ~400 m from the center of LM,
compared with 175m for boulder
c.
Accuracy ~5%, which seems more a matter of luck, given the small
parallaxes available.
v2 is entirely hidden by the rim of
Little West from Pan 3 site
(5913) while, from Pan 4 site (
5936), it is
hidden by
t2. The tip of
v2 is all that is visible
from near the US flag (
5872/73),
from the Pan 2 site on the rim of Double Crater (
5887), and from the
Pan 1 site (
5850).
The size may be roughly estimated from the
December 2009
LROC photo.
v2 actually seems to be a tight cluster of at
least two boulders, which may be parts of a single boulder that
broke apart when it landed. The southern component is the
largest; the length of its shadow suggests a height of 1.5 m or
more. The northern component is about half its height. The width
of each component is ~2 m or more. The group, as a whole,
spans ~4-5 m.
3.3.7 Boulder v3
Closest to the LM of the
v-group. Distance ~120 m, accuracy
better than 2%. In the
December 2009 LROC image, the boulder appears
to be smaller than
t4; so it may be about 0.5 m high
& ~1 m wide. From the LM, it is nearly completely hidden by
a terrain ruga. Only its very tip is discernible in
5872/73,
5850 (Pan 1) and
5887/8 (Pan 2).
3.3.8 Boulder v4
Distance ~140 m, positioning accuracy better than 2%.
v4 is
a small boulder on the rim of a tiny (3 m) crater. Became
discernible only in
LROC images taken from 50 km or lower. Only a
small part of
v4 is seen behind
t3 in
5872/73. In
5913 (Pan 3), it
is completely hidden by
t3 (distance to
t3 is
~18 m). Size of 1 m/1.5 m (height/width), comparable to
t4,
v1,
and
v3. Distance from
t1
~20 m, from
t3 ~18 m, from
t4 ~21 m.
3.3.9 Boulder v5
Distance ~195 m, positioning accuracy ~3%. Seen in
5872,
5887/88 (Pan 2) and
also, very vaguely, in
5913 (Pan 3). Size of 1 m/ 1.5 m
(height/width) comparable to
t4,
v1,
v3,
and
v4.
Distance from
v1 ~31 m, from
t1 ~45 m.
3.3.10 Boulder q1
Detail from AS11-40-5865
showing boulder q1
beyond the southern part of the Little West rim.
This is the only Hasselblad
image taken near the LM that shows all of Little West,
including some of the
interior. (Click on the image for a larger version.)
is a boulder for which a useful photogrammetric location cannot
be calculated from the Hasselblad images but an identification
in the
December
2009 LROC image is almost certain.
q1 is
visible only in
5887
(Pan 2 on the rim of Double Crater) and 5865 (above; taken left
of the ladder during Buzz's egress). These camera stations
are high enough for us to "look over" the rim of Little
West. In a
detail
from 5936 (Pan 4), a yellow dot shows where
q1
would be seen if our view wasn't blocked by Little West.
Unfortunately, perpendicular to the line-of-sight to
q1,
the 5865 and 5887 are only separated by about 2 meters, which is
no more than half the width of the boulder likely to be
q1.
Consequently, a photogrammetrically-determined distance will be
very uncertain. However, a line along the azimuth of
q1
passes
very close to the boulder labelled
q1 on a
detail from the
December 2009 LROC map. A pair of boulders ~40 m WNW from
this boulder are not likely candidates since they are very
probably hidden by Little West; additionally, if not blocked by
terrain, the pair of boulder would appear as a pair from the
direction of the LM. Although we can see numerous boulder closer
to the LM along the line-of-sight in the LROC image, they are
much smaller than my candidate for q1. So I think my
identification is likely to be correct. In this case, the
smaller boulders in front of it are hidden by the terrain.
If the identification is correct,
q1's
range derived from the LROC image is ~260 m. The triangular
shape of the shadow is consistent with the apparent conical
shape seen in 5865 and 5887. Assuming a distance of
260 meters, the portion of the boulder visible 5887 is ~3.6 m
wide and ~2.2 m high. Size estimation by the LROC image
gives width ~3.5m. The visible shadow length is ~14 m.
Assuming that the shadow is resolved and is falling on level
ground, its length corresponds to a boulder height of ~2 m.
3.3.11 Boulder q2
q2
is about 230 meters from the center of the LM and is seen only
in 5865 (above) and
5887.
In the LROC images, it is the only candidate at this azimuth. In
5887, it is adjacent to the bright lens flare; and, in 5865,
only the tip is visible above the rim of Little West. In the
LROC image, another, slightly smaller, boulder is seen only 4
meters north from q2, but it is probably invisible in 5887
behind the sun flare and in 5865 this smaller boulder is
obviously hidden behind the Little West rim. In the LROC image,
the width of
q2 is about 0.5 m while the shadow length
suggests a similar height.
3.3.12 Boulder q3
q3
is about 385 meters from the center of the LM and is seen
indistinctly in 5865 (above) and
5887. The size estimated from the
December 2009
LROC image is about 1 m. There is a second candidate on
the same azimuth, at about the same distance from the LM as
q1;
but this candidate appears is be in a low spot, with
light-colored ground immediately west and dark ground
immediately east. The second canidate also has a short
shadow, indicating that it is not very tall and/or that the
shadow is falling on ground rising to the west.
3.3.14 Boulder q4
q4 is about 410 meters from the center of the LM and,
therefore, is the farthest boulder identified in both EVA
and LROC
images. Being at such a distance, it lies near the
base of the outer slope of the West Crater rim, about 30 m
horizontally from the rim crest. q4 is distinct and well defined in 5865 (above) and 5887, although
we may not be seeing the top of the boulder against dark
outer slope of West Crater.. Both the Hasselblad and LROC
images show the boulder is about 4 meters wide. It is
difficult to estimate the height from the LROC images since
the shadow is cast down slope. In the Hasselblad
images, the visible part of the boulder is about 40 percent
of its width, indiating a height of at least 1.6 meters
