4.3.9 -  Apollo 11: Day 9, Splashdown

The start of the final day of the mission sees a return to colour images, and the first one is from just a short while after the TV broadcast. Figure and 2 have the photo and analysis respectively.

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Figure AS11-44-6674. Source

Figure ESSA-9 (left) and NIMBUS-3 (right) images compared with AS11-44-6674. Below Left is a NIMBUS-3 MRIR HRIR hybrid image. Centre and left are 3D reconstructions of digitally restored ESSA and NIMBUS satellite data respectively. SkySafari estimate of time at terminator is to the right

This photograph is clearly taken not much later than the preceding one from the TV broadcast. Now all of south America has gone, but much of north America is still visible, and the persistent fog banks off California (blue arrow) dominate the view of the northern hemisphere. The large system in the south identified by the red arrow is also visible in figure 4.3.79, but in a slightly different formation, and slightly further east.

SkySafari puts the terminator, just off the east coast of the USA, at around 00:45 on the 24th, some 16 hours before re-entry. ESSA's terminator orbit is track number 3, or orbit 1841, which commenced at 18:02 on the 23rd. Much of the NIMBUS data is either poor or missing for this image, and few features are easily made out. However, the orbital pass over the terminator is still best represented by orbit number 1346, which commenced at 14:28 on the 23rd.

As with the Apollo 8 mission, July 24th is a day that sees the use of a Corona satellite, and three sections of that day’s orbits cover the USA seen in this Apollo image (figure

Figure AS11-44-2674 with Corona pass area highlighted (top left), Corona segments (bottom left), close up of the Corona pass (centre) and Corona images on Google Earth (above)

It’s worth pointing out here that the Apollo image (as well as having brightness and contrast adjusted) has ben rotated to match the Google Earth orientation.

What the corona images show is an area of cloud south of Baja California, broken cloud over the Sonoran desert, and thicker cloud over Utah. While it would be unwise in this case to state definitively that this is exactly what we can see in the Apollo image, there are certainly areas of agreement - particularly the area over Utah. Judging by the cloud shadows the images appear to have been taken around noon, compared with the Apollo image’s late afternoon local time.

The next image of Earth on magazine 38 shows a very similar scene, and was taken only an hour later (if my SkySafari settings are correct) than AS11-44-6674. AS11-38-5712 shown below in figure, and serves merely as a bridge to the next image to be analysed fully, AS11-38-5719 is also shown below in figure, and analysed in figure

Figure AS11-38-5712 (left, Source) and zoomed & cropped (centre) with SkySafari time estimate

Figure AS11-38-5719.  Source

Figure ESSA-9 image (left) and NIMBUS-3 HRIR orbit 1351 (right) compared with AS11-38-5719. Below this are 3D reconstructions of ESSA (left) and NIMBUS IR (centre) satellite data and SkySafari estimate of time at terminator (right).

It should be evident that there are still features visible on this photograph that are also visible on the previous two pictures used from this magazine. The red, yellow and cyan arrows all point to the same cloud features shown in those colours in figure 4.3.99 while the magenta arrow in that figure picks out the eastern end of the band of cloud marked by the green arrow in figure 4.3.102. The banks of fog off the US coast are still visible at the northern end of the terminator line.

ESSA's nearest orbit to the terminator is number 1843 (track 5), which commenced at 21:03 on the 23rd. SkySafari's estimate is that the photograph was taken at 03:30 on the 24th, 13 hours before re-entry. We only have one NIMBUS-3 pass of any use, orbit 1351, which commenced at 01:13 on the 24th. At first glance it does not look too similar to the Apollo image, but it needs to be remembered that it is infra-red, not visible spectrum. If we look more closely (figure, the similarities become much clearer.

Figure Section of NIMBUS-3 HRIR orbit 1351 and the same area of AS11-38-5719

The closer examination makes it much clearer - the time gap between the two images is negligible (remember that the start of the orbit is timed from the poles) and as a result the two images are almost identical.

The last images on magazine 38 are all repeat exposures of the image just examined, and we now return to magazine 44 for our final two images of a full Earth. The penultimate image examined is AS11-44-6676, which is shown below in figure, and analysed  in figure

Figure AS11-44-6676.Source

Figure Main image - ESSA-9 dated the 24th ( far left) and the 23rd (left), and NIMBUS-3 (above) images compared with AS11-44-6676 and SkySafari estimate of time at terminator. Below is the newly restored NIMBUS-3 mosaic ,  orbit 1355 of the HRIR, and 3D reconstruction of ESSA digitally restored data.

As the Earth becomes increasingly crescented, identifying cloud masses becomes a little trickier. The first task here is to identify the landmasses visible on the western limb, and close inspection reveals that we are looking at the east coast of Africa. The blue and green arrows point to clouds over Somalia and Arabia respectively.

Life is complicated even further by the fact that as the image features Africa, the area visible on the western limb features weather patterns shown on the ESSA image dated the 24th, while those over the Indian ocean are the last featured on the image dated the 23rd.  For this reason, sections of both ESSA mosaics are included. The NIMBUS data are poor quality and much of the area visible is either not available or difficult to make out, and for this reason only the blue and purple arrows are used with any confidence, and only ESSA has a 3D reconstruction.

The cloud masses identified by the blue and green arrows are not visible on the image dated the 23rd, but are shown on the one dated the 24th, which helps date things more precisely. SkySafari estimates that the Apollo image was taken at around 12:30 on the 24th. ESSA's nearest orbit to the terminator is number 1848 (track 10), which commenced at 07:00 on the 24th. NIMBUS' nearest pass is number 1353, which commenced at 04:15.

The final image examined, and the final full disc image of Earth taken, is AS11-44-6689, but before we get there we can look at the appearance of Africa in a couple of other photographs taken before it (figure

Figure AS11-44-6678, AS11-44-3.9.11: AS11-44-6685, AS11-44-6687 with SkySafari time estimates

The movement is subtle, but nonetheless there, particularly when you examine the areas around the equator, and Africa’s inexorable march towards the terminator.

The final image examined, and the final full disc image of Earth taken, is AS11-44-6689, shown below in figure and analysed in figure Alongside the still image is a still from magazine M of the 16mm footage.

Figure Main image - ESSA-9 (right) compared with AS11-44-6689 (centre) with SkySafari estimate of time at terminator inset, and NIMBUS-3 IDCS (right). Left - NIMBUS-3 HRIR orbits and 3D reconstruction of ESSA satellite data.

It should be evident to even the least observant that the preceding figure used only one 3D satellite photograph. We do have the restored image from NIMBUS, but the path that is available covering Africa shows very little useful information relevant to the visible part of Africa on the Apollo image. No useful part of ATS-3's view is available. Even with only relatively little satellite data, it is still relatively easy to pick out weather patterns on the image that are different to the ones visible on the 23rd's satellite image.

As for dating the image, the most representative track relating to the Apollo image terminator is number 11, which is 1849, and commenced at 09:05, which compares well with the 14:30 time suggested by Stellarium.

We get few clues from the transcript, but at 193:03 (14:35) we have this from Collins:

193:03:03 Collins: The Earth is really getting bigger up here and, of course, we see a crescent.

193:03:12 Collins: We've been taking pictures and we've still got four exposures to go, and we'll take those and then pack the camera.

As it turns out there were much more than 4, and the remaining images in the magazine are zoomed in much more closely on Earth. The terminator line on these is closer to the African coast, indicating that they were taken after this statement was made. (Figure The terminator line on the 16mm still in figure suggests that it was filmed about 30 minutes prior to the still image, so probably matches AS11-44-6687.

Figure AS11-44-6692. Source

SkySafari suggests this was taken around 30 minutes later than the one examined above.

One thing that is worth examining relates to data supplied by NOAA from their work rescanning and processing ESSA imagery mentioned in the introduction. They supplied an image not in the usual polar projection, but one where all the individual tiles have been overlaid as a flat image - see figure

Figure ESSA 9 image compilation supplied by NOAA (left) AS11-44-6692 Compared with ESSA-9 image flat projection (right)

The backing paper has seen better days, but you can easily identify the landmasses on show. As only Africa is visible in these last Apollo images, it’s worth zooming in on a the African part of this image to see how it compared with the most zoomed in image taken. As you can see there is an excellent match with the clouds in both images, particularly the arc identified by the blue arrow.

Roughly two hours after the Apollo image was taken the CM separated from the SM and the crew began the re-entry procedure. 140 minutes after the image was taken they were in the Pacific, safely away from stormy weather thanks to the satellite images used in this analysis to help prove that they went to the Moon.

So there we have it, the first lunar landing covered from start to finish, with every series of photographs of Earth analysed and compared with satellite photographs to demonstrate that the pictures taken by Apollo 11's cameras could only have been taken where they were claimed to have been taken, including, for the first time, the surface of the Moon.

Having compared a variety of satellite images with photographs covering all parts of the Earth's surface during all parts of the mission, there really should be no more need for any meteorological analysis, but there is always a need for thoroughness.

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