4.3.6 -  Apollo 11: Day 6, Footfall

At around the same time as the last Earth image on day 5 was being taken, the decision was made to start the EVA procedure, and a few hours later at 02:56 on the 21st of July, 109 hours and 24 minutes after launch, Neil Armstrong sets foot on the Moon. 

While Aldrin & Armstrong worked on the lunar surface, Collins continued his orbits around the Moon and captured another Earthrise image on magazine 44 in AS11-44-6604 (figure This picture occurs immediately after photos of the LM after separation, and later on in the magazine there are images of the LM ascent stage returning, so this image must have been taken before 17:54 on the 21st. The photograph is compared with ESSA & NIMBUS satellite images in figure

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Figure AS11-44-6604. Source

Figure ESSA-9 (top left) images compared with AS11-44-6604. Below this are NIMBUS-3 IDCS (left) and HRIR (right) image. Below this again are 3D reconstructions using digitally restored data from ESSA (left) and NIMBUS (right) satellite data, and SkySafari estimate of time at terminator.

 A small subsection of the above is examined in

Figure Section of NIMBUS-3 HRIR orbit 1310 compared with the same area on AS11-44-6604

According to the mission transcript, at 4 days 14 hours and 7 minutes (or 110 hours 7 minutes or 03:39 GMT) & 20 minutes after the start of orbit 18 Capcom contacts the CSM to confirm AOS, which Collins acknowledges some 30 seconds later (it maybe that his message to Houston is not a confirmation of AOS, but querying Houston as to whether he had it).

SkySafri has been set at 03:45 on the 21st, and there is a clear match with the photograph in terms of Australia's position and the position of Columbia. As with previous photographs where Australasia is featured, the ESSA image featured is not from the 21st but from the 20th, and the NIMBUS image is a composite of strips from the 20th and 21st, The timings will be examined shortly. As far as the weather patterns that are visible are concerned, the system picked out by the green arrow in figure 4.3.49 has moved from a position south of Victoria state to one covering New South Wales coastline. The detail in figure of the cloud circulation around North Island New Zealand is superb. The clouds over Japan and off the coast of east & south east Asia have persisted, but have changed configuration from figure 4.3.49.

For the satellite timings, ESSA 9's track 8 is the nearest one to pass the east coast of Australia. The ESSA composite dated July 20th shows this track (orbit 1809) as commencing at 04:03 on the 21st. As mentioned previously, the two passes available from NIMBUS covering the area shown in the Apollo image are picked from orbits 1309 and 1310. The former is shown on the composite image dated the 20th, the latter on the composite dated the 21st, these were commenced at 22:02 on the 20th and at 23:50 on the 20th respectively, several hours before the start of the EVA and the Apollo image.

Meanwhile on the surface, Armstrong and Aldrin are collecting samples and installing a variety of scientific equipment. They take many photographs, three of which show the Earth (two of these are the same scene taken twice).  The first of these images to be analysed here is AS11-40-5924 (figure, which is done in figure This is the other photo examined by Aulis that we mentioned earlier in day 5’s analysis.

Figure AS11-40-5924. Source   50Mb TIFF version here

Figure ESSA-9 compared with AS11-40-5924, 3D reconstructions  and SkySafri estimate of time at terminator.  

The weather patterns in shown in the image taken from the surface are a clear match with the ones taken from the orbiting CSM, although there is more detail observable in the clouds, particularly over Australia, and satellite timings will be the same. To save cluttering up the page, I’ve only added the ESSA image with arrows, but feel free to scroll up and check.

The first check to make now to justify that choice is to see whether it is the same view of Earth or not, and figure compares Australia's position in AS11-44-6604 and AS11-40-5924.

Figure Comparison of Australia's position in AS11-44-6604 and AS11-40-5924

Australia has evidently moved between the two images (the white arrows are the same length), and this movement is consistent with the suggested half an hour time gap between the time of AOS in Collins' orbital image and the Stellarium estimate of time in the ground based picture. It’s also worth noting the position of Columbia in the SkySafari depcition, showing it to be well past Tranquility Base. At this pointin the mission he is relaying his attempts to see the site back to Houston. While he’s doing that, the timeline and mission transcript shows Aldrin engaged in photographing the LM landing gear, and  AS11-40-5924 occurs between a series of images of the LM structure. It seems entirely reasonable that while moving around the base of the LM to capture the effects of the landing on the structure Buzz should look up and see the perfect photographic opportunity. Everything ties together perfectly.

The next photograph of Earth is AS11-37-5506, which is shown below in figure, and analysed in figure

Figure  AS11-37-5506.  Source

Figure AS11-37-5506 compared with ESSA (top & bottom left) and NIMBUS and NIMBUS HRIR-3 image (centre left) and 3D reconstructions using digitally restored ESSA (centre) and NIMBUS IR (right) satellite data. SkySafari time estimate is to the left

This photograph is the only successful attempt of several made to take a picture of the Earth from inside the LM. As the flag and astronaut footprints are visible in the images preceding and following this one, it is reasonable to assume that the crew are back inside the LM after their EVA, so this photograph must have been taken sometime after 05:11, when the LM hatch was closed but before returning to orbit.

Despite the lower quality, brought on both by Armstrong photographing the Earth through the LM window and mis-focussing the camera, it is still possible to identify features common to the ESSA image, and that were also visible in figure 4.3.58, and only the blue and cyan arrows differ.

The weather system that started off south over Victoria State before moving east of New South Wales appears to have progressed further eastwards, although it is difficult to tell how far. What is evident is that Australia has moved further eastwards with the Earth's rotation, consistent with being taken  90 minutes later than the previous image, and also fitting in with the timeline of the mission. By 05:45, the time suggested by SkySafari's terminator, the crew had been back inside the LM for around 30 minutes, but 90 minutes later the Hasselblads were jettisoned on the lunar surface to save weight. No more images could have been taken from the LM after that time.

The ESSA orbit at the terminator corresponds to track 8, or orbit 1809, and was commenced at 04:03, so the satellite's orbital progress is matching Earth's rotation as seen from the Moon. The clouds picked out by the red arrow were imaged at 00:18 by NIMBUS.

The next view of Earth requires a little speculation and interpretation. It comes in the form of an Earthrise sequence shown in magazine D of the 16mm footage - see figure

Figure Still from 16mm footage taken between lunar lift off and docking with the CSM

The magazine starts with lift off from the lunar surface and after the Earthrise shows the CSM approaching, so the Earthrise must be some time between launch and docking. As will be seen below there is footage already from the CSM, as well as clear still images, that even while the view in the figure above is blurry obviously shows very different scenes. The reunion of Eagle with Columbia didn’t occur until three and a half hours after lunar lift off, which gives time for at least one orbit before docking. Earthrise for that would have been at around 19:30, and as can be seen in figure this puts south America firmly in shot.

SkySafari shows us that the main landmass that ought to be present is South America, with the bulk of the top half of Earth being the north Atlantic. On the western limb is the eastern seaboard of the USA. Africa and western Europe would just be visible on the north-eastern limb. If we have it worked out correctly then we should have an area of cloud showing off Africa and in the south Atlantic off south America, with large amounts of cloud off the west coast of South America and the USA’s east coast. Figure 4.3.63 shows that this is not an unreasonable interpretation of what we have, although I am the first to admit it is less than conclusive.

The next usable image of Earth comes from a fantastic sequence of Earthrise images taken as the LM ascended towards the CSM. The Apollo Image Atlas only has poor quality images of most of this event, but the ALSJ has better ones. There is also a large TIFF image of AS11-44-6642, available from this site: archive.org. The ALSJ high quality version is shown in figure, with a close up of a similar view from the 16mm footage included, scanned from ‘Life’ magazine’s Apollo 11 special and my own copy. The still image is analysed in figure

Figure ESSA 9 images dated 21 July 1969 compared with still from Apollo 11 16mm footage and SkySafari suggestion of time at terminator. Below these are 3D reconstructions using digitally restored ESSA (left) and NIMBUS (right) satellite data.

Figure AS11-44-6642 (top  left). Source b) 16mm video still as shown in Life Magazine (far left), and my personal copy of a NASA original (top right) and a zoom of the Earth from that original (above)

Figure Row 1 - AS11-44-6642 and ESSA-9. Row 3 - ATS-3 (left) & zoomed crop of a 16mm still from this video. Row 2 - NIMBUS-3 (left) images NIMBUS-3 HRIR (right). Row 4 - 3D satellite reconstructions and SkySafari time depiction.

We also have some close up views from satellite images contained in reports - see figure

Figure Section of AS11-44-6642 compared with close up of ATS-3 image over the Caribbean area from the BOMEX study, a section of orbit 1318 from NIMBUS-3 and an ESSA 9 image .

Dating this photograph within the official chronology is pretty straightforward. The transcript at the ALSJ has this:

127:51:36 Collins (onboard): [Garble] I got the Earth coming up already. It's fantastic!

and records the photograph as taken immediately afterwards.  LM AOS is reported shortly afterwards. The MET equates to 21:24, and this is the time set on the SkySafari view.

As far as satellite timings are concerned, the ATS-3 image is unambiguous, stating clearly that it was taken at 14:11, some 5 hours before the Apollo image. The closest ESSA orbit to the terminator in south America is track 3, orbit 1816, commencing at 18:00 on the image dated the 21st. The NIMBUS orbit for the same area is orbit 1319, which commenced at 15:54.

It is, as usual, obvious that the Apollo image matches the satellite images for the date in question, displaying distinct features not visible in the same configuration on preceding or subsequent days. Particularly obvious are the large 'X' shaped formation over the north Atlantic (marked by the blue arrow in the preceding figure), and the elongated 'C' shape to the south-west of Chile marked by the magenta and purple arrows. Even in the relatively poor quality scan of Life magazine’s video still, the curl off Chile, the ITCZ clouds, and the ‘X’ of cloud across north America are still easy to make out.

Fog banks are also visible off the coast of California and Chile that differ in shape and extent from other days in the mission. Figure shows that the formations in the Caribbean off the northern coast of south America are also identifiable.

On the subject of Chile, another satellite image is available covering that area for the 21st, as mentioned in the introduction to this section (shown in figure, along with part of AS11-44-6642. The image in question is from a summary report of the 5 years of uninterrupted meteorological observation by satellite. It is unclear which satellite is the source of the image (it could be one of several), but it is certainly much clearer than the ESSA or NIMBUS views used so far. The high degree of correspondence between the lines of latitude, longitude and various points of the storm system on this image and the ESSA image used in the previous analysis suggests this is a higher quality version of the ESSA 9 data. The image is clearly labelled the 21st, and is evidently a photograph of print-outs, as the cut allowing two piece of paper to be overlapped is obvious cutting across the storm and individual lines from the printer ribbon can also be made out.

Figure Unnamed satellite image of Chile and part of AS11-44-6642. Newly restored NIMBUS-3 ISDC (left) and HRIR negative (below right) added for comparison

Although this adds little to the overall analysis, it is again an illustration that very fine detail can be picked out on the Apollo images with an educated eye, and also that the sources of satellite information were never a secret.  This particular image was used to pass on information about a storm in an area that was poorly covered by conventional forecasting, and part of the reason for the report in which the image was printed was to point out the usefulness of satellite data in meteorology, something that was still being evaluated.

While storms were gathering off Chile, the LM ascent module was heading towards the CSM to re-unite the three crew. After that re-union, we head for day 7 and the start of the journey home.

Intro Day 1 - 16/07/69 Day 2 - 17//07/69 Day 3 - 18/07/69 Day 4 - 19/07/69 Day 5 - 20/07/69 Day 6 - 21/07/69 Day 7 - 22/07/69 Day 8 - 23/07/69 Day 9 - 24/07/69 Synoptic
Intro Day 1 - 16/07/69 Day 2 - 17//07/69 Day 3 - 18/07/69 Day 4 - 19/07/69 Day 5 - 20/07/69 Day 6 - 21/07/69 Day 7 - 22/07/69 Day 8 - 23/07/69 Day 9 - 24/07/69 Synoptic