4.5.6 - Day 6: Homeward Bound

While there are no more images to be used from magazine 60, there were still other magazines being used. Magazine 62 features image AS13-62-8977, which can be seen in figure 4.5.6.1 (Source: AIA ).

Figure 4.5.6.1: AS13-62-8977. (Source given in text)

It is always a source of amazement that a figure such as the photograph presented above can contain all the information needed to repel a conspiracist's argument. Ostensibly containing nothing, this photograph, and countless like it, contain sufficient detail of the Earth's weather systems to prove that they were photographed at the same time, or at least within a few hours of, a satellite in orbit much much closer to the subject. Figure 4.5.6.2shows the ESSA satellite in comparison with this Apollo photograph.

Figure 4.5.6.2: AS13-62-8977 in comparison with ESSA satellite image and 3D reconstructions of ESSA and NIMBUS IR data, and SkySafariestimate of time at terminator.

The terminator is falling across the west coast if the USA, and this allows the time of the photograph to be estimated at 02:00, which must therefore be on the 16th.

The main feature on this photograph is obviously the large sweep of cloud that has been a persistent feature over the entire mission, and this has extended from the relatively tight curl centred over Alaska to a much broader sweep. Despite the blurred image, the large swathe of wispy cirrus clouds off Baja California are still very much evident. What is also apparent is that the weather patterns identified by the blue and cyan arrows are noticeably further apart in the ESSA image. Although this may be a product of the angle at which the Earth is being viewed and the distorted perspective of the satellite composite's projection, but it could also be that the weather has moved on between the satellite image's exposure and that of the Apollo photograph.

ESSA's most representative terminator orbit is track 4, which runs along the west coast. This would be pass number 5165, which commenced at 20:07. Examination of the records show pass 5166 is not listed in the data catalogue, and this is either because of some technical problem and data from the surrounding orbits has been used to fill in the gaps (there is a degree of overlap), or it has been missed when generating the list. If the latter is the case, it should have commenced at around 22:00, over 4 hours before the Apollo image was taken. Pass 5167 started just after midnight on the 16th.

The final image that attributable to the ESSA composite from the 15th and its attendant satellite analysis are shown in figures 4.5.6.3 & 4 respectively, and involves AS13-62-8993.

Figure 4.5.6.3: AS13-62-8993 (Source)

Figure 4.5.6.4: AS13-62-8993 compared with ESSA and NIMBUS satellite images. 3D reconstruction of digitally restored ESSA data and SkySafari estimate of time at terminator

The land in the centre of the image is the Indian sub-continent, with Arabia on the western Horizon. The bulk of the visible cloud mass is sweeps over the Himalayas before meeting with another weather system crossing northern India from the Indian Ocean. The terminator line falls roughly across Bangladesh on the coast, and this gives an estimated time for the image of 11:30 on the 16th.

ESSA's pass over this part of the world is best represented by orbit 5171 (track 10, which intersects the Bangladesh coastline), commencing at 08:09 on the 16th. At this point in the journey, the crew were busy dealing with repeated problems with one of their batteries, and preparing for the final course correction that would put them in the correct alignment for re-entry.

It’s often documented that Apollo 13 witnessed a tropical storm on re-entry, and that this was Tropical Cyclone Helen - a storm that they were already aware of before the incident as it was in a potential landing site in an unexpected early abort. These things were always planned for! Despite these claims there is no actual mention of it by the crew other than in passing when discussing their landing zone, not re-entry. Here’s the exchange between Jack Lousma as Capcom and LMP Haise:

112:38:39 CC: The weather prediction for your landing area is still good; 2000 scattered, high scattered; 4-foot seas, 15-knots wind. There's a hurricane 500 miles to the west, which doesn't pose a problem.

112:39:02 LMP: A hurricane or a typhoon?

112:41:24 CC: Belay my last. It's degraded to a tropical storm.

The time for that comment is about 11:45 on the 16th. The storm threat is discussed in this Universe today article, complete with photograph of Mission Control staff poring over a weather map, and one member of that team discusses it in the article. It’s possible that the discussion is buried somewhere in the tape loops here, but it’s very likely that reports of the crew seeing Cyclone Helen are based on remembering scenes in the Apollo 13 film.

An interesting diversion is provided by the image used in that Universe Today article, which is also available in slightly higher quality here. Figure 4.5.6.5 shows the image in question, which is captioned as showing the flight control team examining a weather map to when working out landing zones.

Figure 4.5.6.8: AS13-62-9012 (Source)

Figure 4.5.6.9: AS13-62-9012 compared with ESSA satellite images and SkySafari estimate of time at terminator.

The weather front identified by the green arrow is very obviously the same one picked out in numerous previous images, but is also obviously a development of that system and not a reproduction of it. There are, as is often the case, subtle differences between the satellite images and the Apollo photograph that are indicative of a time gap between them.  Several more images after this, up to AS13-62-9034 show a similar but slightly rotated view (see figure 4.5.6.10).

The position of the weather front off the north African coast allows us to put a time of around 19:15 for this second image.

ESSA's best path covering these photographs is track 13. In this case this would be orbit 5174, commenced at 14:05 on the 16th.  The crew are now 24 hours away from a safe landing and are going through the housekeeping and entry procedures that will see them through those final hours.

The final image of Earth in magazine 62 is AS13-62-9038 (Source). On the next page, figure 4.5.6.11 shows this image as shown in the Apollo Image Atlas, and 4.5.612 and b shows the analysis of the weather patterns in it. The terminator line is now runs down through the centre of the north Atlantic, clipping the eastern coast of Brazil. This places the time of the photograph at roughly 20:45, and as the cyan, green and blue arrows point to the same weather systems shown in the previous image, the Apollo image must, therefore, be from the 16th of April.

Figure 4.5.6.10: AS13-62-9034 compared with SkySafari time estimate

Figure 4.5.6.12: AS13-62-9038 compared with ESSA satellite images and SkySafari estimate of time at terminator. Blue, green and cyan arrows as in figure 4.5.6.6. Left is the ESSA photograph as published in the Sarasota Herald Tribune published on the 17th.

Figure 4.5.6.11: AS13-62-9038. Source given in text

Back to the matter in hand.

Once ESSA's satellite passes over eastern Africa, it starts a new page, and any images taken by Apollo will therefore be referenced by an ESSA composite labelled the 16th.The first in the final day's images is AS13-62-9012, (figure 4.5.6.8). The image shows another development in the life of the weather system that has lain off the Europe and north Africa over the course of the mission, and the position of the terminator gives an estimated time of the Apollo photograph of around 18:00. The satellite image used is dated the 16th, and the analysis in figure 4.5.6.9 demonstrates that this is the appropriate date for it. Sadly, no reconstructed data are available for the date in question, so no 3D image is possible.

Figure 4.5.6.5: Flight control staff examining a satellite image. Source.

Figure 4.5.6.6: Comparison of ESSA image taken on April 15th with the one in figure 4.5.6.5.

Is it possible to work out which satellite image is being used? Well, if we rotate the image and stretch it so that it’s more like the view they have of it it, it looks like the view presented in figure 4.5.6.6, which is shown with the actual satellite image that was commenced on April 14th, but completed on April 15th.

The small bright spot of cloud is Tropical Cyclone Helen, as pictured sometime around 04:00 on the 15th. The main concern for the forecasters was that changing the location of the landing had implications for when a course correction burn could be carried out, and this was not a mission where resources were limitless. By the time that satellite image had been taken they were confident that the chosen spot would be OK and that they could use re-entry procedures to help avoid the area. As Helen’s track still wasn’t absolutely certain and they organised lots of reconnaissance flights to make sure - as detailed in this report. Indeed the New York Times was already reporting on the 15th (and therefore knew about it on the 14th) that:

“A tropical storm named Helen near the New Hebrides about 1,700 miles away was being watched closely by Navy weather experts. It was not expected to interfere with the planned recovery.”

As for the Apollo 13 the movie, as tension builds before re-entry RETRO (the flight control member responsible for all matters re-entry) alerts Kranz to the storm in the landing area (which we now know to be a hefty bit of dramatic licence). The camera pans down to what is supposed to be a satellite image on his desk. Apart from the fact that the image is colour (no colour satellites existed at that time), the photographed used is actually form Gemini V in 1965 (see figure 4.5.6.7). Rather than showing the south Pacific, its actually the Hawaiian islands.

Figure 4.5.6.7: Still from ‘Apollo 13’ and Gemini V image S65-45616_G05-H.