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4.4.4 -  Apollo 12 Day 4, lunar encounter

Heading towards their lunar encounter, we have almost an entire day without images of Earth. As we’ll demonstrate below the view is of weather systems East of the ones pictured on day 3, so they automatically have to be taken on day 4. Figure shows AS12-50-7385, and figure the satellite comparison.

Figure AS12-50-7381. Source

Around 24 hours since the last view of Australia and there is again a change in the configuration of the large frontal cloud mass south of Australia that extends up from the Antarctic (magenta arrow). The two distinct branches of the plume have gone, and smaller lobes extend off into the Australian interior than was the case the previous day. Australia is just visible on the western limb, and this puts the time of the image at around 04:30 on the 17th. The red and crimson arrows match figure

ESSA's orbit nearest the terminator is 3293 (track 6), which commenced at 23:09 on the 16th. Australia itself would not have been imaged completely until 05:05 on the 17th (track 9, orbit 3296). NIMBUS is even further behind, at least for the visible spectrum images, which covered the terminator at 19:25 (pass 2903) on the 16th, putting the NIMBUS satellite some 10 hours behind the Apollo one. This would help to explain the discrepancies in some areas between the cloud patterns that are easily identifiable on the Apollo and ESSA images, but not the NIMBUS ones (eg the blue and green arrows). Night time infra-red images did cover the area nearer the time (around 03:00 on the 17th), but the quality of the image is much poorer, so little would have been gained in exam

In the next photograph (AS12-50-7391) Australia is very obvious, which makes it an obvious candidate for comparison with satellite images. Figure shows the Apollo image, and shows the satellite comparison.

Figure ESSA-9 (left) compared with AS12-50-5788. Below that it is NIMBUS-3 IDCS (centre) and HRIR (right), and 3D reconstruction using digitally restored ESSA data (right). SkySafari estimate of time at terminator to left.

Figure AS12-50-7385. Source

Figure Main image shows AS12-50-7385 compared ESSA-9. Below are NIMBUS-3 IDCS (right) and HRIR (right) images. Bottom row are 3D reconstructions using digitally restored ESSA (left) and NIMBUS-3 (centre) satellite data and Stellarium estimate of time at terminator (right).

With no land masses present, the only time reference available to us is the terminator cutting across the large cloud bank in the southern Pacific that ends up around New Zealand, and the time works out at somewhere around 02:45 on the 17th. This estimate would put the mission time at around 58:22. A couple of hours earlier they were discussing weather conditions on the west coast of the USA:

055:40:01 Lind: Roger. What does the weather look like out there?

055:40:10 Bean: Looks beautiful. See it real well. It doesn't appear to be any clouds - any large cloud formations near it. There's a nice crescent-shaped large weather system that appears to be several hundred miles out to sea, but I don't know if that will affect it or not. But the whole area around that southern tip of California there is nice and clear.


056:04:53 Bean: Been looking at the Earth some more through the monocular, and I think maybe the part of the U.S. that I thought was the lower left-hand corner, the Los Angeles area, it was just about to have sunset, was really not. I don't think I could see that because of the - it's color-related to the blue of the rest of the Earth. I think maybe it was the desert area around Phoenix and around in there, just thinking about the time it is now. And I'm not able to discern at all the lower left-hand corner of the U.S., I think, because of the colors.

056:05:38 Lind: Roger. A little smog out there in L.A.? Can't see through it?

056:05:47 Bean: No. I don't think its smog. I can't see any of that area. I think it's probably just that the Earth out there has more trees, shrubs, and the like, and that makes it sort of a gray-green which is sort of like the ocean whenever you look at it from this view. And they just blend in together, and you're not able to tell exactly where one starts and one ends. We noticed that a little bit as we were closer to earth and then now as we get out this far, about all we can see is something contrasting very greatly with those blue-grays or blue-greens. In this case, it was sort of a reddish-brown [garbled]...

It’s difficult to tell which crescent system he;s referring to, but there is quite a large in the north Pacific, the tale end of which is picked up by the cyan arrow above.

The time stamp for that conversation makes it around midnight GMT, and the SkySafari time depiction in figure shows that they would indeed have been looking at LA.

NIMBUS' daylight visible spectrum view over the east coast of south America would be from orbit 2916, which commenced at 20:06 on the 17th. Depending on how accurate our estimate of the time is the NIMBUS coverage on the 16th could be closer to it time by a couple of hours, but the coverage provided by that day’s picture is not as good.

ESSA's best fit pass for the same area is orbit 3289 (track 6) 23:09 on the 16th. Once again, an Apollo image shows weather patterns that are only visible at a specific time on a specific day.

The next series of Earth photographs occur immediately before two images of a distant lunar far side of the moon as Apollo 12 approaches LOI. That photograph is shown in figure, and analysed in figure

Figure SkySafari depiction of Earth at the time of the above conversation.

Figure AS12-50-7391. Source

Figure Main image shows AS12-50-7391 compared with ESSA-9 (top & bottom left). Below this is NIMBUS-3 IDCS (left) and HRIR (right). Left are 3D reconstructions of digitally restored ESSA (lfar left) and NIMBUS (left) satellite data. Stellarium estimate of time at terminator is above.

The position of the terminator on the very edge of eastern Australia puts the time of the Apollo image at around 08:15.

What decides the date of this image is the large pointed weather system off western Australia (picked out by magenta and yellow arrows on the satellite images. ATS-3 does not cover this part of the globe, so we are restricted to NIMBUS & ESSA for our image supply. The system off western Australia does appear on the visible spectrum NIMBUS image, but this does not show the areas north of Australia, and for this reason the daylight infra-red image has been used, which does show it. The NIMBUS pass over Australia is 2907, which commenced at 03:24 on the 17th, giving it a few hours head start on the Apollo image. The system in question was imaged by NIMBUS at around 04:43.ESSA's best fit orbit is number 3296 (track 9), which is found on the image dated the 16th, but was actually started on November 17th at 05:05.

We get additional confirmation of the time from a TV broadcast made on the 17th between 07:14 and 08:10. While the broadcast was being sent through Goldstone in California, Australia got the show live through their own receiving stations, and the crew confirm that Australia is centre stage:

063:34:11 Gordon: Hey, Jerry, I have the Earth again. Is that a better picture?

063:34:15 Carr: That's a much better picture. [Pause.]

063:34:29 Conrad: That landmass you're looking at there is Australia.

063:34:32 Carr: Roger. We can't..determine anything on the Earth there, but it looked quite a bit more like the Earth now than it did before. It looks like you got it stopped down considerably more.

063:34:51 Carr: 12, Houston. The word is Australia is getting your TV show live.

063:34:59 Conrad: Roger. They're getting it live, and I wish they could see their landmass. It's almost right in the middle of the Earth. And they ought to recognize the snow cap of South Amer - of the South Pole just below them.

064:07:54 Conrad: It's amazing how well you can see when you're looking at something you recognize. I got the monocular here, and I'm looking at Australia, and I can see 80-Mile Beach and the area that that's in - and, the area that Shark's Mouth Bay just south of Carnarvon's in. It's very clear over in that part of Australia right now.

We can have a quick look at a still from that TV broadcast in figure (derived from a better quality source), with some of the same features from identified:

Figure Still from youtube video of newscast featuring Earth, and cropped and enhanced version of Earth with features identified as in figure

While the quality is obviously not as clear as the still image, there is sufficient resolution to allow for identification of some the same features.

It is also worth noting that between this and the next sequence of Earth images there are two photographs of the Moon. They are noteworthy because they show the Moon in a completely different phase to that visible from Earth. Figure shows the Moon from AS12-50-7389 (Source). The CSM is approaching the Moon on an intercept course that will place it in an east-west orbit (as viewed from Earth), and hence is looking towards the moon from the west, not face on as in the Stellarium view. It’s further evidence that the Apollo craft was not looking at the Moon from a terrestrial perspective.

Figure The Moon as seen from Apollo 12 shown in AS12-50-7389 compared with Stellarium's view from Earth at approximately the same time. The red arrow identifies the same crater, and the Moon has been rotated to the correct position.

The Apollo Image Atlas identifies this image (and the one following it) as showing the 'far side' and before the CSM's first lunar orbit ('Pre-REV 1').  The latter is definitely true, but at least half of the lunar disk would be visible from Earth. The fact that the other half could not is still significant.

We next have an isolated view of Earth taken on a new magazine to discuss. Magazine 51 starts with a large number of images of the lunar surface looking straight down, placing it firmly in lunar orbit. AS12-51-7489 features a very distant shot of Earth, immediately after which comes a sequence of images showing the LM after separation, which means it has to be before 04:16 on the 19th.

Image 7489 must therefore have been taken before separation at 04:16 on the 19th, and after LOI at 03:47 on the 18th. As with the previous image, the image is out of focus and blurred, with only large scale systems can be identifiable, but there should be sufficient detail to demonstrate the point. Figure shows the original image and figure the satellite comparison.

Figure AS12-50-7394 (Source)

Figure AS12-50-7394 compared with ATS-3 (centre right), ESSA-9 (top left) and NIMBUS-3 IDCS (centre left, NIMBUS HRIR strips (centre middle) and 3D reconstructions using digitally restored ESSA (far left) and NIMBUS (left satellite data. Above is Skysafari time estimate. Right is the satellite photograph published in the Sarasota Herald Tribune on the 18th, but taken on the 17th

Timing the image is relatively easy thanks to the west coast of South America being just visible, and most of north America, which allows SkySafari to put the time at around 23:00.

The most obvious features are the large circular cloud off Chile picked out by the cyan arrow (and the attendant flecks of cirrus clouds west of that that are visible once the circular feature disappears in to the night portion of the globe), the long finger of cloud stretching from the Antarctic north-westwards towards the equator (blue arrow), and the bifurcated equatorial cloud mass in the northern hemisphere picked out by yellow & magenta arrows.

The ATS-3 image is timed at 14:43 on the 17th, and as a result only those weather systems off the west coast of South America can be identified with any degree of confidence, but they are nonetheless identifiable. Both the NIMBUS and ESSA images are dated the 17th. The most representative daylight IR passes for NIMBUS is2915 for figure 4.4.14, which were commenced at 16:54. NIMBUS imaged the clouds identified by the blue arrow at 19:02. ESSA's most representative passes are tracks 4, pass 3304, commenced at 20:07. Once again the suggested timings for the Apollo images are completely vindicated by the timings of the satellite photographs.

The next photograph in the magazine is also of Earth, but it was taken after midnight so click the link for day 5 to see it.

The key weather systems here are the two identified by the green and cyan arrows off the western coast of Australia. The system picked out in blue is just off the Sumatran coast, which also helps to narrow down the location of the terminator, as does the weather system over Arabia (yellow) on the edge of the disc, and the one over Sri Lanka (red arrow). It is unfortunate that this weather system crosses the boundary between two day's ESSA data, and more unfortunate still that there is not as much overlap between the two day's data shifts in terms of longitude (so that we can't use the data from the next day to corroborate), but you can't have everything. The NIMBUS view does show that we have the correct weather system in our sights. The best estimate for the terminator position here gives a time of approximately 11:00 on the 18th. ESSA's best orbit from this image is orbit 3310 (track 10) which was actually commenced at 08:09 on the 18th, while NIMBUS' best available orbit is 2922 which commenced at 05:25 on the 18th. The orbits covering Australia exactly do not feature clear images, or are absent.

A time of 11:30 would put the still joined spacecraft in lunar orbit after the second circularisation burn. This is supported by the first few images in the magazine, which shows an initially lit lunar surface over Mare Nectaris (on the eastern near side), followed by darker frames, then a brightly lit one of Mare Nubium in the south-east before the darker frames and then the photograph of Earth. The position of the lunar terminator (as documented here) supports a time of around 11:30. In fact the terminator position caused a re-assessment of the time of this photograph, as it was initially thought to feature Australia more prominently, putting it far too early in the process. Were this the case, areas shown to be just lit on the lunar surface would have been in complete darkness. 11:00 would equate to 90:00 MET, so we would be on the near side and not long before LOS - pretty much in the right place for the post terminator photography.

One final images will be examined from magazine 50 today, the penultimate one taken before LOI. Figures and have the photograph and analysis respectively.

Figure AS12-51-7489 (Source)

Figure AS12-51-7489 compared with ESSA (top left) & NIMBUS-3 HRIR images (far left). Centre left is a 3D reconstruction of digitally restored ESSA data.  Stellarium estimate of time at terminator above.

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