4.4.3 -  Apollo 12 Day 3, Trans-Lunar Coast continued.

There’s a long break now until the next photograph of Earth, and the first one we get to look at is shown in figure, with an analysis in figure They occur in the magazine before photographs of a fouled window in the CSM.

Figure AS12-50-7367. Source

The photographs of the fouled hatch were taken sometime after 02:15 GMT, as this is the time that (according to the mission transcript) instructions on how best to photograph the windows were supplied by Capcom. They were first described to Capcom on the previous day, but are gone over in more detail half an hour prior to the photography instructions, so we have a latest time for the photographs of around 01:45.

We also have descriptions from the crew of the terminator crossing Florida (although they do describe difficulties in determining land features) at around midnight GMT on the 16th:

031:43:04 Conrad: Looking at the Earth down there, Houston, it looks like you are littler than a golf ball at arm's length now. Sure looks pretty though. The terminator looks like it's - it's kind of hard to tell from this distance - looks like it's passing somewhere just west of Tallahassee.

It is difficult to tell for them, as obviously the termiantor has moved well beyond Florida at this point. We also have these comments:

032:05:31 Gordon: We've been trying to look at the United States through the monocular, and it just looks like most of the States is covered with clouds. Are you having bad weather generally over the country?

032:05:47 Carr: We'll have to take a look at an overall map, but here in Houston, it's been CAVU all day and beautiful, a wonderful, clear fall day.


032:07:03 Carr: 12, Houston. I've got a weather map here for the United States. All up through the northeast part of the country it looks like it's either overcast or broken. And then in the Southeast and in the South and up through about the panhandle of Texas down into Florida it's all clear. And then, moving on further west, you get into New Mexico, Arizona, California, and you begin to pick up overcast skies again, all the way from Montana all the way down to Arizona. Montana has got a few broken and scattered clouds in the eastern side and then it's pretty bad over on the western side.

032:07:49 Gordon: Yes, we - we could - We were having a hard time picking out exactly where we were looking at. Even with the monocular everything is now - tends to be brown - and having a hard time picking out the land from the water, but it seems like that part of the country that we can see is pretty well covered with clouds.

With this in mind we have a time for the photograph already of somewhere between those two, putting SkySafari at 01:00 on the basis that no land masses are easily visible in the Apollo image, and using the position of the weather systems on the 3D maps.

Assuming a terminator line just off the west coast of north America, this would mean that the best ESSA orbit corresponding to that would be orbit 3280 (track 5), which commenced at 22:00 on the 15th. The equivalent NIMBUS pass is number 2889, which commenced at 18:18 on the 15th. The magenta arrow points to a cloud system imaged at 20:22 on the 15th, which is also shown in the image and matches exactly the NIMBUS tile.

The next image to be examined is AS12-50-7377 and is shown in figure It appears after the photographs of a fouled hatch window, which again gives us the starting point for working out when it was taken, and Earth appears much smaller in the viewfinder now. The satellite comparison is shown in figure

Figure AS12-50-7377. High quality source: AIA.

Figure Main image - AS12-50-7377 compared with ESSA (left top & bottom). Below this is a 3D reconstruction of digitally restored ESSA data (right) and NIMBUS HRIR (centre). Left are NIMBUS daytime IR strips (left) and SkySafari time estimate (left).

The NIMBUS data in the preceding image is night time infra-red, which has the only complete coverage of that part of the globe on that date. The orbit that best represents the terminator here is number 2897, which commenced at 10:28 GMT on the 16th. Shown above for comparison are the two passes of daylight HRIR available, and the pass that ends at north Australia started at 01:56.

As for ESSA, the Apollo image terminator is mostly covered by track 6, or orbit number 3281. This pass was commenced on the 16th at 00:05 and appears on the image dated the 15th. 

The date of the 16th can be confirmed convincingly by the weather pattern over south-eastern Australia, which does not appear in that configuration on any other date, and is a clear development of the system identified by the purple and magenta arrows in figure The next set of Earth photographs is a series of 4 showing the same view, and the first of these, AS12-50-7381, has been selected from this batch for comparison with the satellite images.

It is shown below in figure, and analysed in figure

Figure AS12-50-7381.  Source

Figure Main image - ESSA-9 (left) images compared with AS12-50-5381. Below this are NIMBUS-3 HRIR (left) and 3D reconstructions using digitally restored ESSA (top right) and NIMBUS 3 (top right lower) satellite data. Bottom are day time HRIR images (right), with SkySafari estimate of time at terminator (above).

The distinctive plume of cloud below Australia (marked by the yellow and magenta arrows) has moved much closer to the terminator than in the previous analysis, which allows a more precise estimate of the time of the image. Stellarium puts this photograph as being taken at around 07:00 GMT.As with the previous image, the night time infra-red image has been used for NIMBUS coverage, as this has the best data for the region on that date.. It does mean that, as before, the cloud patterns visible on the NIMBUS mosaic are a reflection of the thermal conditions of the atmosphere, rather than what can actually be seen.

The NIMBUS orbit nearest the terminator is number 2897, which was started at 09:50 on the 16th. ESSA's terminator orbit is number 3283 (track 8), which commenced at 04:06 on the 16th.

We have another conversation with the crew to support the timings:

040:02:56 Gibson: How's that cloud cover over the Pacific at this time?

040:03:02 Conrad: Well, Australia is real clear again, and it doesn't look quite as cloudy north of Australia. It's sort of a - It's got a rectangular shape to it, whatever the system is north of Australia there. It's kind of funny looking.

040:03:23 Gibson: Roger. What's the smallest piece of land you can pick out? Can you see any of the Pacific islands?

040:03:34 Conrad: [Laughter] No, we haven't - We can't see any of them. One of - Dick just says he can see Borneo right now. He's looking through the monocular.

040:03:46 Gordon: You can't see it with your naked eye, though.

040:03:51 Conrad: I think one of the problems is that - The only thing that we could see would be close to the curve. All the - the terminator - We're not looking at that much of an Earth and all the water in the Pacific that's close to the terminator has a very shallow Sun angle on it, and it's fairly washed out.

040:04:19 Gibson: Roger. You still getting a pretty good glint off the surface then?

040:04:25 Conrad: Yes. Dick says the subsolar point is just west of Australia. By the way, how far out are we now?

Borneo is certainly visible, and the subsolar point. Just on the Timor Sea here would indeed by west of Austalia by the time of this conversation (around 08:30 GMT).

A few images later in magazine 50 there is a short sequence of images that can be identified by the cloud patterns as somewhere east of Australia. This automatically puts it almost a day after the previous image, so we move on to day 4.

Figure ESSA-9 (top left) and NIMBUS-3 (centre left) images in comparison with AS12-50-7367. In the centre middle are NIMBUS HRIR passes. 3D reconstructions using digitally restored ESSA ( bottom centre) and NIMBUS (bottom left) satellite data. Centre right are an individual NIMBUS 3 tile and a close up of the same area on the Apollo image, identified by the magenta arrow. Bottom right is a SkySafari estimate of time at terminator. Left is the satellite photograph published on November 16th by the Sarasota Herald Trbiune

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