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4.2.4 Apollo 10 Images – Day 4: May 21st

The first image from the 21st is AS10-34-5070, and is shown below in figure The comparative analysis with the satellite images is shown in figure

Figure AS10-34-5070. Source

Figure ESSA 9 (top left) and NIMBUS 3 (centre left) images compared with AS10-34-5070. Below these are ESSA (left) and NIMBUS (centre 3D models built using digitally restored data and SkySafari time estimate.

The quality of the image is such even without zooming in it is possible to see that the system identified by the blue and green arrows in the previous analysis are still visible in this one, but  the systems shown by the purple and magenta arrows have moved beyond the terminator, and are no longer visible. There is no need to use the ATS image in the analysis, as in there is only the fog banks off the west coast of northern America that is still visible on it.

In terms of when the image was taken, SkySafari suggests a time of around 02:30 on the 21st, at which point the crew were roughly at the point where the Moon & Earth appeared the same size to them, and not far off the point where they passed from the Earth's gravitational sphere of influence and into that of the Moon's.

ESSA's most representative orbit for the terminator is track 5, or pass number 1011, which commenced at 22:00 on the 20th. NIMBUS' pass for the same area is number 490, commenced at 20:17 on the 20th.

Now that the Earth has rotated a little more it’s worth looking at the higher resolution infra-red images from NIMBUS. For this image there have been issues with the NIMBUS data, and there are sections missing, but it is still possible to focus in on the western limb and the weather systems surrounding Japan (see figure

Figure Section of NIMBUS-3 infra-red orbit 493 compared with section of AS10-34-5070

As usual with these things the Apollo record and that of NIMBUS are an excellent match. Particularly worthy of note is the circular depression in the top right of both images. While no name storm is given in this area for these dates, it is certainly very obvious. This particular pass was started at 01:20, almost exactly matching the estimate for the Apollo photograph.

Not long after AS10-34-5070 was taken, the crew entered a rest period, and it is some time before any new photographs are taken. The next image of Earth in magazine 34 shows a view of Africa, which obviously means some time has elapsed on the ground. This image is AS10-34-5071, and is almost identical to image AS10-35-5190. For the sake of continuity, 5071 will be used and is shown in figure AS10-35-5190 can be seen here. AS10-35-5190 is the last image in that magazine before the lunar surface in close-up begins to appear, which helps narrow down the timeline somewhat.

Figure  AS10-34-5071. AFJ Source

Figure shows the analysis, and the most obvious weather systems visible are those in the northern hemisphere, particularly the striking spiral off the coast of Africa (red arrow), and the complex frontal system indicated by the blue and green arrows. Neither of these features were evident on the previous day's satellite images, although they are obviously a development of the systems visible in figure from the previous day.

Figure ESSA 9 (top left upper and lower), ATS-3 (bottom left) and NIMBUS 3 (bottom right) images compared with AS10-34-5042. Below are 3D reconstructions using digitally recovered ESSA (left) and NIMBUS (centre) data and SkySafari time estimate.


SkySafari suggests a time at terminator of around 16:15 on the 21st. South America is visible in the Stellarium image, but it is difficult to spot in the Apollo image until it is spied under a thin layer of cloud. The yellow arrow points to a triangle of cloud that will be more visible in later images.

ESSA would have imaged the terminator area in track 12 of its orbit. As the image dated the 21st starts with the area covered by track 11 onwards, this means that orbit 1051 is relevant pass, commencing at 12:07 on the 21st. NIMBUS' equivalent is orbit 497, commenced at 08:49 on the 21st.

We have good coverage of this image from the higher resolution NIMBUS-3 infra-red imagery, as seen in figure

Figure NIMBUS-3 infra-red orbits 497-500. Colours used match figure Above is the MRIR version of orbit 500, showing the missing portion from the HRIR image.

As usual the infra-red imagery is an excellent match for that of Apollo. Particularly noticeable is the swirl of cloud off the Iberian peninsula. The missing portion in the final pass is covered well by the MRIR instrument. And the large band of cloud off the northern US is easy to make out. As we have northern Europe back in the frame, we can also look again at the area around the UK, as shown in figure

Figure Section of NIMBUS-3 orbit 498 compared with AS10-34-5071.

Once again, even when zooming into the smallest details the match is exact. The UK can me made out in the centre of the Apollo image, and the Atlantic fronts marching in are easy to make out. The distinctive swirl off Spain is very obvious.

Before the final Hasselblad is examined, we have one more TV sequence to look at. This sequence was broadcast between 17:26 and 17:43 on the 21st. A still from a CBS news broadcast is included in the analysis below (figure It isn’t all that clear, so a still from this source is also included.

Figure Cropped screenshot of Apollo 10 live CBS TV broadcast with ESSA & NIMBUS images from 21/05/69, and SkySafari insert showing terminator position at time of broadcast. Below these are ESSA (left) and NIMBUS (right) 3D models built using digitally restored data. Below these are ESSA (left) and NIMBUS (right) 3D models built using digitally restored data. Right is a clearer version of the same scene.

As usual with the TV broadcasts there is a detailed description of the scene:

072:38:15 Stafford: Right. You can see the South Atlantic Ocean there and the orange spot to the right is the North African continent. You can see basically the Sahara Desert and, above that, the Mediterranean Sea. The rest of the world is pretty much encased in clouds. The solid cloud cover that's covered the North Pole, and most of Europe, is still with us today. At this time, as we look at the Earth, we are 210,000 miles [389,000 km] away. We've only got about 9,000 miles [16,700 km] to go to the Moon and we're traveling approximately 2,500 miles an hour [4,600 kph] relative to the Earth. Also, in about 15 minutes we will enter the shadow of the Moon and make our major burn to enter lunar orbit in approximately 3 hours. Now, at this distance, the Earth looks slightly smaller than a tennis ball to us and a little bit larger than a golf ball. And I hope it shows up the same way on your screen.

072:39:19 Stafford: ...And again, South Africa - Go ahead, Charlie.

072:39:27 Duke: Roger. I was just going to add that we can see the northern part of Africa. We had a bluish tint to it at first but now it's coming in to a sort of orangish brown and we can see the South Atlantic and the cloud covers very well. The colors are very good. Over.

072:39:47 Stafford: Roger. Again, the Sahara Desert, the Atlas Mountains, Morocco, Libya we can see from here. It is an orange brownish orange. The night time - the terminator has cut across the Suez Canal and most of Egypt and is now covering most of South Africa. I can see Spain. It is a greenish brown and is completely contrasted with respect to North Africa. However, you may have difficulty seeing it on your set due to resolution at this distance. Again, you can see Brazil, but it is covered mostly with clouds at this time... At this time Apollo 10 is going through the preparation for the Lunar Orbit Insertion burn, and the next - After we lose contact with the Earth, the next time that we come around, we will – To have contact with the Earth, we'll be at approximately a 60- by 170-mile [111- by 315-km] orbit around the Moon. Right now, we cannot see the Moon, even though it is rapidly accelerating us towards itself by its mass. Over.

072:53:32 Stafford: Looks like we're right on trajectory, then. Okay. Here's another look at the Earth through the 210-foot dish at Goldstone, and I hope the colors are coming through a little better. Again, the west coast of North Africa is still a bright orange, and the central part of North Africa is starting to turn purple as night-time approaches over the western part of Libya and the eastern part of Tunisia. Again, it's awful hard to see Spain because Spain is a greenish brown this morning. You have the Mediterranean and the Atlantic covered with some clouds, so it's awful hard to see any part of Spain. But again, the Earth to us this morning looks a little bit smaller than a tennis ball as we're 210,000 miles [389,000 km] from the Earth and now less than 9,000 miles [16,700 km] to go to the Moon.

We also have available another 16mm view of Earth, very obviously taken at the same time (figure

Figure 16mm Apollo 10 still.

One final photograph can be examined before coming to those featuring the Earth with the lunar surface, and this is AS10-34-5072, the last in this magazine before pictures of the lunar surface are featured.  This photograph is shown below in figure, and analysed in figure

Figure AS10-34-5072. AFJ Source

Figure ESSA 9 (top left upper & lower), ATS-3 (bottom left) and NIMBUS-3 IDCS (bottom right) images compared with AS10-34-5072. Below are 3D reconstructions using digitally recovered ESSA (left) and NIMBUS (centre) data and SkySafari time estimate.

SkySafari suggests an image time for Apollo of around 18:15. The ESSA orbit for the mid-Atlantic region is number 1053 (track number 1), which was at 15:08. The NIMBUS 3 track for the same area is orbit 500, which was started at 14:11. Again the NIMBUS orbit precedes the other two images. Conversely, the weather systems identified by the blue and green arrows were taken at the roughly same time as the Apollo image. Orbits 501 & 502 by NIMBUS occurred at 15:59 and 17:46, while orbits 1055 & 1056 (tracks 3 & 4) were at 19:08 and 21:03.  ATS-3 images were taken at 17:17.

It should be clear from the Hasselblad still that it is showing the same weather details that can be seen in the TV and 16mm footage.

We have a gap now of almost 24 hours while the crew enter lunar orbit and prepare for the big rehearsal, so click the link below to go to day 5.