4.1 Apollo 8
Apollo 8 is of significance because the astronauts on board became the first people to see the far side of the moon, and the first to witness an Earthrise: the apparent rising of the Earth from below the Moon's horizon as the orbiting spacecraft reached Mare Smythii in its passage around the Moon. This phenomenon had, of course, already been witnessed by Soviet and US unmanned probes, but to be captured by human eyes added more significance to the event.
The mission was launched on 21/12/68, reached lunar orbit on 24/12/68, and re-
ESSA 7 images are available in this document: ESSA 7 data catalogue. I actually own a hard copy of this and confirm that the online scan is absolutely accurate. ATS-
4.1.1a Apollo 8 Still images – on the way to the Moon
The first magazine containing images of Earth is number 16. This magazine is notable because it contains images from all stages of the mission from initial low earth orbit, separation of the Saturn IV-
Figure 4.1.1: AS08-
Figure 4.1.2: ESSA-
It is also taken very soon after separation from the Saturn IV-
It is also worth noting the shadow under the linear cloud mass near the terminator over north Africa (picked out by the green arrow). The direction of that shadow under the clouds is consistent with the sun's direction at sunset.
Stellarium (an astronomical software package used to identify the location of celestial bodies: http://stellarium.org) can be programmed with times and locations. In this case, using the lunar surface as a view and changing the date to the 21st gives a time for the Apollo image of around 17:15, shortly after the initial separation from the SIV-
"..it's a beautiful view with numerous cloud vortex..I can still see the Cape and isthmus of central America"
ESSA 7 data suggest that South America would have been photographed by the satellite at about 19:09, as this was when track 3 (pass number 1594) of the satellite's daily orbit over it was commenced. The time over the terminator area would be more covered by track number 1, orbit 1592, which commenced at 15:05. At the time of the Apollo image, then, it would be another 2 hours before the satellite would image the area photographed, and there would be a further few hours on top of that before all the visible Earth was covered.
The next in the series of images taken showing any significant change in the scene below them is AS08-
Figure 4.1.3: AS08-
Figure 4.1.4: ESSA-
In this image, the long shadows are cast by the clouds over the Amazon, and the yellow & purple arrows point to the same weather systems as they do in the previous figure, although only the thin tail curling away from the yellow arrow system is still visible.
Much more prominent now are a large spiral system off the north American coast and below Alaska (green arrow), and the scattered clouds over the south Pacific. There is also a prominent plume of cloud heading northwards from Antarctica (magenta arrow), and a small whirl of cloud off south America (red arrow) that are all easily found on the satellite image, along with all the other weather patterns.
The Earth has rotated by a consistent amount between the first two photographs analysed, the shadows lengthen at the terminator, and the weather systems are still visible from the previous image. The bright spot showing the sun's reflection can be seen in this image, and the perspective of the photographer has changed noticeably, with much more of the Antarctic region in view.
Stellarium suggests a terminator time of around 20:45 on the 21st. The ESSA track over the terminator region was commenced at 17:00, as this was when track 2 (pass number 1593) began, as discussed for AS08-
Figure 4.1.5: AS08-
Figure 4.1.6: ESSA 7 (left) and ATS-
Although there is no land visible in the image, it is possible to mark the position of the terminator with Stellarium by using the previous image analysis as a reference. The weather system highlighted by the green arrow is the same in figure 1.1.6 as in figure 4.1.4, which means that the terminator is just about on the west coast of the USA, which puts the time at around midnight on the 22nd. This corresponds well with the ATS-
Stellarium also indicates that Australia should be visible on the western limb. This part of the Apollo image is a little washed out, but the magenta arrow points to a band of cloud that should lie off Australia's east coast and that is visible in all 3 images presented here.
The presence of that green-
No specific mention of the actual time of the photograph, but the transcript does have the crew querying what settings they should be using on the camera, and stating at around 01:00 that:
“This PTC attitude isn't the greatest for taking pictures of the Earth”
PTC stands for 'Passive Thermal Control', or the 'barbecue roll' slow rotation that allowed the CSM to balance its temperature in direct sunlight.
A few hours later, we have the next image of Earth showing movement, AS08-
Figure 4.1.7: AS08-
Figure 4.1.8: ESSA-
The rotation of the Earth in this photograph compared with the previous one is such that the ATS image no longer has any features that are visible in it, and the only weather system identified in the previous image that is also identifiable in this one is the one picked out by the magenta arrow.
The system picked out by the blue arrow in figure 4.1.6 can still be seen on the satellite image, just as the green arrow here identifies a weather pattern that was visible on the ESSA part of figure 4.1.6, so it is obviously a continuation of the weather observations on the day. The plume of cloud extending up from Antarctica (yellow) is very easy to pick out in the Apollo image, as are the streams of west trending clouds to the west of it (purple and cyan arrows), the 'Y' shaped pattern near the equator (red arrow), and the Himalayan clouds (blue arrow).
Stellarium shows that the terminator is showing a time of approximately 07:00, and this can be compared with an ESSA time for the orbit nearest the terminator of 02:05 (orbit 1598, track 7).A couple of images later in the magazine we have another new image of Earth, this time showing Africa as the dominant land mass in view. AS08-
Figure 4.1.11: AS08-
Figure 4.1.12: ESSA-
The green and purple arrows in figure 4.1.12 point to the same systems shown in figure 4.1.10, and the thin swirls of cloud discussed previously are now clearly in view (red arrow). Similar thin wispy bands of cloud can be seen off the coast of south America (south of the cyan arrow).
For the first time in this section, an ATS-
ESSA's orbit best matching the terminator is number 1606 (track 2) which commenced at 18:05, just 55 minutes before the Apollo photograph, which Stellarium puts at 19:00.
Ostensibly, the ATS & Apollo images seem (terminator line apart) identical, but there are subtle differences. The clouds over the always dynamic Amazon climate system, for example, are in a different formation to Apollo's, where they are much more similar to the ESSA image taken nearer the time. There are also differences in the way the twin streams of cloud picked out in red are shaped. In ATS-
A short while after AS08-
Figure 4.1.13: AS08-
Figure 4.1.14: ESSA-
As suggested previously, little has changed in the weather systems already shown, but it does serve to show (again) that the Earth is rotating as the CSM gets further away, and that that rotation brings into view weather systems that were previously hidden. There is no change in the ATS-
Stellarium suggests a time for the image of 21:30, just 90 minutes after the previous one, and all of the colours for arrows to identify weather systems in figure 4.1.12 apart from the green and red ones are used again. The reader is also referred back to figure 4.1.4, which showed the same view roughly 24 hours earlier, and where magenta is used to identify the same weather pattern. Those two day's weather patterns are compared below in figure 4.1.15.
Figure 4.1.15: AS08-
The two days’ images show what is obviously the same weather system, but that has developed over 24 hours to extend further northwards, while a frontal band to the west moves further eastwards towards Chile.
Next up in the sequence of images is AS08-
Figure 4.1.18: AS08-
Figure 4.1.19: ESSA-
The Earth has rotated sufficiently to lose the ATS-
The ATS image was actually taken at 22:43 on the 23rd, over 20 hours after the Stellarium estimate of the image time, and understandably there is a much bigger difference between the Apollo image and ATS-
Of those systems, the most striking ones are at the northern and southern ends of the planet. In the north there are the two frontal bands (green and red arrows) marking the boundaries of lighter swirls of cloud between them. To the south there are the storms heading north from the Antarctic, including the striking tight curl of cloud marked by the yellow arrow, and the long band of cloud making its way to Australia's east coast.
ESSA is a much better match for the Apollo image, and this is explained by the images being taken much closer in time to it. Orbit number 1609 (track 5) is the closest to the terminator, and commenced at 23:00 on the 22nd.
The next image in the magazine (AS08-
Figure 4.1.20: AS08-
Figure 4.1.21: ESSA-
While the Christmas day 1968 is the very latest that the picture could have been taken, the satellite record places the photo graph very definitely on the 23rd, with Stellarium placing the time at 21:00 on that date. ATS-
At 55 hours of mission elapsed time (MET), or about 19:55 on the 23rd, the crew gives confirmation of what is in the photograph by describing the view as seen through the TV cameras in their second transmission to Earth:
"..what you are seeing is the western hemisphere...I can see Baja California and the south-
Looking at the Apollo photograph, they are describing accurately what they can see, and have not (as in all cases when discussing the view of Earth on any mission) been prompted in any way. The long cloud heading north-
The next images from Apollo 8 are from lunar orbit. Click the buttons below to navigate there or elsewhere.
Figure 4.1.9: AS08-
Figure 4.1.10: ESSA-
As usual, the weather patterns on the satellite images correspond exactly with those on the Apollo image, and several of the cloud systems visible in this image will be seen in later ones, not least the spectacular 'dog-
Although the Apollo image is slightly out of focus, it is still possible to pick out the thin clouds over north Africa (eg the cyan arrow), the coastal cloud banks around southern Africa, the typical frontal system off South Africa itself (yellow arrow).
The astronauts themselves describe the view to the ground at exactly the same time as this image was taken:
"This is a mighty nice view we have down there today, A little bit more than a half Earth. Looks like Africa and the Red Sea is visible we're not quite sure as there is quite a bit of cloud cover."
Stellarium suggests a time of around 14:00 on the 22nd for this image. ESSA's nearest track to the terminator is track 11. This is orbit number 1602, which is labelled as the first orbital pass on the image dated the 22nd, and was commenced at 10:05 on the 22nd. The ESSA satellite would barely cover the area around the terminator before the Apollo image was taken, never mind the rest of the photograph.
The next image in the magazine, AS08-
Figure 4.1.16: AS08-
Figure 4.1.17: AS08-
We’ve now moved on a couple of hours, and the Rocky mountains are beginning to disappear into night. There is no direct reference to the photograph being taken, but roughly an hour later communications issues led to Hawaii being asked to send messages, suggesting that the Pacific view in the photograph is consistent (as we would expect) with the mission narrative.
The area shown is an intermediate one between the those covered by ATS-
As the time suggested by Stellarium is 23:30. The ATS-
ESSA’s image is a much better match than either of the ATS satellites, as its orbital pass is much closer in time. The closest pass to the terminator is number 4, or pass 1608, which started at 21:05.
The next image of Earth is AS08-