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Tsiolkovskiy crater, processed raw film scan from Apollo 13

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#1 Tom Glenn

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Posted 15 April 2020 - 05:53 PM

The Apollo 13 mission to the Moon occurred 50 years ago, and there have been a number of interesting websites to document this anniversary.  One such example is linked below, which allows you to follow along with the mission, as it occurred in real time, with communications audio, annotated transcripts, commentary, and photographs.  You can fast forward to any part of the mission you like.

 

https://apolloinrealtime.org/13/

 

As most of you know, the Apollo 13 mission experienced a severe incident en route to the Moon, which significantly crippled the spacecraft, and the crew had to abort the planned lunar landing and return to Earth under very challenging and dangerous conditions.  Instead of entering lunar orbit, the spacecraft passed once around the Moon to slingshot back to Earth.  A number of interesting photographs were taken during this mission, despite the challenging conditions.  In looking over the website linked above, one that caught my eye was a photograph of the crater Tsiolkovskiy, a very nice crater on the lunar far side, named after the scientist Konstantin Tsiolkovskiy, famous for developing the equation that bears his name (Tsiolkovskiy rocket equation) that relates propellant mass and exhaust velocity to the impulse delivered during a rocket burn.

 

I had long been aware that all of the Apollo mission photographs had been scanned, and were available on the web.  Most of the versions you will find are provided as processed images, and are only available as 8 bit files.  I discovered one excellent source, however, that provides the raw film scans, unprocessed, as 16 bit tiff files.  That source is below, and is a collaboration between NASA, the Johnson Space Center (JSC), and Arizona State University (ASU).  

 

http://apollo.sese.asu.edu/index.html

 

Particularly interesting is reading about the scanning process.  There are a variety of file formats that you can download, but only the raw film scans are unedited.  These images are all in the public domain, and you can process and use the images for non-commercial purposes, including personal use, education, or research.  I downloaded the raw film scan of the image I had been searching for of Tsiolkovskiy.  The raw film scans are very large files, about ~1.3 GB for a single file.  

 

http://tothemoon.ser...mm#AS13-60-8625

 

The image was taken with a Hasselblad medium format camera (70mm film), and a 250mm f/5.6 Zeiss lens.  The film used was Kodak Ektachrome SO-368, which was custom made for NASA.  No details are given about the exposure, but it's very noteworthy how dark the raw film scan appears (see below)!  I then did a series of adjustments to the image of the raw scan, and cropped and rotated the final version.  In the next post, I will give a brief outline of those procedures.  You can find numerous other processed versions of this image on the web, and there is nothing remarkable about mine.  This was simply done out of interest to look at the raw film scans, and the historical context given that the image was taken almost exactly 50 years ago.  Click for larger size of the second image.  

 

AS13-60-8625-film-small.jpg

 

AS13-60-8625-final-TG.jpg

 

 


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#2 Tom Glenn

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Posted 15 April 2020 - 05:58 PM

As I stated above, the raw film scan was very dark, shown again below.  The entire image is contained in the bottom 5% of the raw histogram for the tiff file.  

 

AS13-60-8625-raw-scan.jpg

 

I applied a gamma 2.2 curve to this raw image, which barely made a dent in the brightness, but did make it slightly visible.  

 

AS13-60-8625-gamma.jpg

 

This image was adjusted with 2.5 stops of exposure increase.  

 

AS13-60-8625-exposure.jpg

 

This was subsequently adjusted with an additional non-linear curve, approaching a standard "film" curve.

 

AS13-60-8625-curve.jpg

 

The next step was a crude white balance and black level adjustment.

 

AS13-60-8625-white-balance.jpg

 

The steps above were all performed in RawTherapee (which is free) and then the image was exported to Photoshop for final adjustments.  


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#3 SMigol

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Posted 15 April 2020 - 06:18 PM

Amazing how much information is hiding in that bottom part of the histogram.

 

Are all the exposures of this film so very dark?  I wonder if that was by design to eliminate reflections from halation.



#4 Lacaille

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Posted 15 April 2020 - 11:01 PM

Gosh that is interesting- thanks Tom!

#5 Foc

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Posted 15 April 2020 - 11:41 PM

Excellent exposure of historical moon detail



#6 Tom Glenn

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Posted 16 April 2020 - 03:34 AM

Thanks Stephen, Mark, and Ross.  There are certainly a lot of interesting things that one could discuss here.  Regarding exposure, I'm not a film expert, but it does seem to me that the raw scan is underexposed, especially considering the wide latitude that film has that protects against overexposure.  I'm not sure, however, to what degree the scanner itself affects the representation of the data.  I did look at other images in the archive however, from other missions with the same camera (only a few, because of the huge file sizes and download times) and they are definitely not all underexposed.  In fact, some look almost normal in raw form, with only a simple curves adjustment required.  But again, I'm no film expert.  The 70mm Hasselblad's were being operated in a semi-automatic mode, with manual selection of targets by the astronauts, but some of the exposure parameters were automated.  And obviously, with lots of other things going on at the time (certainly during Apollo 13), it could just be that many images are underexposed.  The info page describing the scans mentions how a custom made 14 bit scanner was used to transfer the data.  That certainly helps here. 

 

Also interesting is that the colors are way off in the original scan, as you can see above.  Furthermore, the colors were not even across the image, making it impossible to white balance, and therefore a complete artistic interpretation on my part, although that appears to be what everyone has done with these images (link here).  There are hot pixels distributed throughout the image, that were clearly introduced by the scanner.  Also present are blemishes, hairs, etc, which I did not remove.  

 

Many interesting things are noticeable to me in the image itself.  The first is that the amount of film grain is very high, even in the reduced size image.  In fact, the image posted here retains all of the original detail, despite being downsized to about 15% of the original scale.  Some of this is because of the low exposure, and some probably because of the film itself, and then also the scanning process oversampled the film grain.  Judging from this particular photo, the 70mm film had about a 57mmx57mm square that was exposed, and the scanner is reported as having 5um pixels, which puts the raw image at 11,300 pixels across in each dimension.  As I said, the 1600 pixel image posted here captures all the available data.  

 

Also interesting is to compare the image to amateur images taken from Earth.  I'm reminded of views of Pythagoras that we get near the limb, that present a similar profile to this image of Tsiolkovskiy.  The absolute resolution of the image here is actually somewhat lower than many images taken from Earth (at least of Tsiolkovskiy itself.....elements near the front of the frame are higher resolution because of perspective that we don't have from Earth.....everything on the Moon is essentially equally far from us, but not from the perspective of a spacecraft).  But there are certain features that I nevertheless like better about this image.  Absent is the forced look that many amateur images have.  The film grain is very pleasant (too much denoise makes images look plastic).  Also, the fact that the optics were not operating near their diffraction limits means that diffraction artifacts are not present (no ringing).  Certainly, however, a modern camera, even a consumer DSLR, could take a sharper image today from the same location above the Moon.  But most importantly, this photo represents a moment in time, captured by humans, on a dangerous and epic voyage beyond Earth, trying to get home safely.  


Edited by Tom Glenn, 16 April 2020 - 03:38 AM.

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#7 DMach

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Posted 17 April 2020 - 10:01 PM

But most importantly, this photo represents a moment in time, captured by humans, on a dangerous and epic voyage beyond Earth, trying to get home safely.  

Well said!

 

Thanks Tom for posting all of this, really interesting stuff and a fantastic result.

 

It also looks back to a time where everything was done using good old film ... those days where 1) changing things like ISO was not such a simple matter and 2) you didn't know for sure what the result would be until you developed the film lol. 

 

So much has changed ...



#8 sunnyday

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Posted 17 April 2020 - 10:08 PM

interesting and fascinating.thanks.



#9 Tom Glenn

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Posted 18 April 2020 - 01:57 AM

Thanks Darren and Sunnyday for the additional comments.  The Apollo images are interesting for a variety of reasons, many of which are the obvious historical interest in the missions and their place in human history.  Also, there is an additional interest from the standpoint of image processing, and comparison to todays methods.  The 50 year old film images hold up quite well over time, despite significant advances in technology.  Finally, one of the many advantages of the internet is that the general public now has easy access to data that would have been difficult, if not impossible, to acquire years ago.  And this last point is true not only for the Apollo missions, but also for more recent NASA missions.  You can access almost anything very easily these days.

 

According to the data available at the Apollo 13 site linked at the beginning of this post, the image of Tsiolkovskiy was taken at a distance of 690km from the Moon, with the spacecraft traveling at a speed of 8518 ft/s, or Mach 6.9, relative to the Moon.  The astronauts were traveling in the lunar module, using the LM as a life boat, because the service module was damaged, and the power in the command module had to be conserved for reentry.  If the accident with the oxygen canisters in the service module had occurred on the return trip after the LM had already been discarded, they would have died.  The descent propulsion system of the LM, which normally would have been used to slow the LM from lunar orbit into a decent trajectory for landing, was instead used for a series of unplanned rocket burns to alter the path of Apollo 13.  One of these burns was used to speed up the return trip by about 12 hours, which ensured the recovery zone was in the Pacific Ocean, where the U.S. military had its ships positioned (because that was the original plan before the accident).  

 

As an indicator of the speed at which the spacecraft was traveling, the photograph below was taken approximately 44 minutes after the first one I posted, with the same camera, 250mm lens, and film (although it was the next film magazine).  You can now see the entire Moon, with Tsiolkovskiy at the bottom of the image.  Most of the features visible on the top half of the lunar disk are visible from Earth, with the bottom half corresponding to the far side.  Also noteworthy, is that this image has the Reseau marks (cross marks for calibration) that are found on almost all Apollo images. The first image I posted did not (even on the raw scan), and none of the images from that film magazine had any.  I'm not sure why, but perhaps the Reseau plate wasn't properly put in place for that magazine, and then was corrected in the next one.  

 

AS13-61-8765.jpg



#10 Luc CATHALA

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Posted 18 April 2020 - 02:40 AM

Hello Tom

The problem came from the scanner because this image is perfect in the series of photos of Apollo 13 in any case thank you for all this informations and your work.

 

https://www.lpi.usra...e/?AS13-60-8625

 

Clear skies.

Luc



#11 Luc CATHALA

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Posted 18 April 2020 - 02:44 AM

Hello Tom

Wouldn't the problem come from the scanner because this image is perfect in the series of photos of Apollo 13 in any case thank you for all this informations and your work.

 

https://www.lpi.usra...e/?AS13-60-8625

 

Clear skies.

Luc



#12 Tom Glenn

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Posted 18 April 2020 - 02:51 AM

Hello Tom

Wouldn't the problem come from the scanner because this image is perfect in the series of photos of Apollo 13 in any case thank you for all this informations and your work.

 

https://www.lpi.usra...e/?AS13-60-8625

 

Clear skies.

Luc

Hi Luc, I guess I'm not sure which problem you are referring to.  The image you link is a processed version of the same film.  Most likely from the same scan, because I doubt they would take these out of the vault too many times.  I don't think you will find too many differences from the image you linked and the one I originally posted at the top, other than mine is cropped and rotated, and the color balance is a bit different.  Also, some of the central peak is clipped to white in your link.  The sky has also been reduced to nearly all black (both in mine and your link) although there is a non-uniform intensity level, increasing as you go to the left of the image, and with more blue.  If you look at the raw film scans you will see that the background is almost never black in any of these photographs, and is usually not uniform either.  Some of this is probably from the film, and some may be from the scanner.  My intention in showing the film scans above was not to correct any of the underlying defects in the raw scan, which is why all the artifacts are still present.  The versions of the images at the website you have linked to are almost certainly all from the same scans, but are processed into a more final version, cropped, and background subtracted.  In my first image posted at the top, however, I did reduce the background to nearly uniform black.  


Edited by Tom Glenn, 18 April 2020 - 03:08 AM.


#13 Tom Glenn

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Posted 18 April 2020 - 02:54 AM

And certainly the vertical line artifacts and patches are from the scanner.  Most of what you read about processing these photographs say that the background was subtracted, and indeed, most processed versions that are published show black backgrounds.  But the original scans aren't that clean.  This is also observed in the image above showing the entire Moon.  I wonder if light was leaking through on the left side of the scanner, and the left side always seems to have lighter regions.  


Edited by Tom Glenn, 18 April 2020 - 02:56 AM.


#14 Tom Glenn

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Posted 18 April 2020 - 02:59 AM

And that image can also be seen here:

 

https://www.lpi.usra...e/?AS13-61-8765

 

Notice that if you look at the higher resolution file, you can see that the background is green in that version.  It's very difficult to get a any type of color accuracy from these images, 



#15 Tom Glenn

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Posted 18 April 2020 - 03:13 AM

Also, I linked this above, but the section containing details on processing that was performed (not by me, but by others) is copied below.

 

http://apollo.sese.a...CANS/index.html

 

"The scans of the Apollo flight films are processed using a standard set of procedures. First, the unexposed portions of the film along the edges of a scanned frame are cropped, and the frame is straightened. Second, the background is removed from all of the scans, by assuming that the average DN values of the unexposed regions at the edge of each raw scanned image represent the background (i.e., film base and fog). Third, a flatfield correction (derived from the actual image data) removes vignetting to the first order. Fourth, the reseau patterns (the small crosses visible on Apollo images published elsewhere) are removed from the images. Fifth, a logarithmic histogram transformation is applied to the image. This is necessary because of the logarithmic response of film, which makes the raw scans appear very contrasty. Since photographic paper also has a logarithmic response and reverses the films response, conventional paper prints have a natural contrast range. The logarithmic histogram correction applied to the scanned images therefore produces a virtual print that simulates the natural contrast of a conventional paper print. Sixth, since the uncompressed images produced by the initial scanning process result in extremely large images, the scale is reduced by a factor corresponding to the square root of 2, which serves to reduce the image size by 50%, and the images are converted from 16-bit to 8-bit. The original, unprocessed raw scans are also provided on this website in full-resolution 16-bit TIFF format. More details about the file formats are provided in a following section."



#16 Tom Glenn

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Posted 19 April 2020 - 02:08 AM

And here are a couple of additional interesting views of Tsiolkovskiy, this time taken from Apollo 15.  This crater is unique among far side craters, because of the darker lava flooded floor.  The lava flows that created this effect were common on the near side, but not so much on the far side.  The central peak is very impressive, rising over 3200m from the crater floor.  One of the many interesting things that one finds when looking over the old Apollo transcripts, is that the astronauts were just as excited to see these craters as any of us might be.  In fact, it's very easy to imagine being onboard the mission, and glued to the windows taking photographs.  

 

The photographs below were taken in succession, on the same film magazine for the Hasselblad 70mm camera.  In looking over the images, I did a few simple trigonometric calculations to approximate the spacecraft location, and was concerned that my calculations were off, because I was obtaining an altitude well under 40km, which is below the average reported orbital altitude of Apollo 15.  Fortunately, I was able to locate some mission transcripts, and find that these images were taken after a "decent orbit insertion" burn, which reduced the spacecraft altitude in preparation for lunar landing.  So my estimations were not so far off.  Copied below, from the linked website, is the transcript corresponding to this time on the Apollo 15 mission, and the crew makes special mention of Tsiolkovskiy.  In the transcript below, "Scott" refers to David Scott, commander of Apollo 15, and "Henize" refers to Gordon Henize, an astronaut serving as mission control in Houston. 

 

https://history.nasa...unar_orbit.html

 

"083:15:53 Scott: Okay. Burn status report. Burn was on time. Burn time was about 24.0 - about half a second shorter than predicted. There was no trim; residuals were plus .6 [fps], plus .0, minus .1; Delta-Vc, minus 4.4, fuel 29 - 29.25 [percent of full]; and the oxidizer 29.55; unbalance, 100 increase.

 

083:16:34 Henize: Thank you, Dave. We copy all that.

 

083:16:41 Scott: And I'll tell you, it's really spectacular, when you can see the central peak of Tsiolkovsky coming up over the horizon before you see the rim.

 

083:16:51 Henize: Hey, that's an interesting astrophysical observation.

 

083:17:59 Scott: And, Houston, 15. The G&N [Guidance and Navigation computer] had us in a 58.4 by 10.0 [nautical mile, 108.2 by 18.5 km orbit].

 

083:18:08 Henize: We copy, 15."

 

Raw Film

 

AS15-91-12382-raw-film.jpg

 

My edits

 

AS15-91-12382.jpg



#17 Tom Glenn

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Posted 19 April 2020 - 02:09 AM

Raw film

 

AS15-91-12383-raw-film.jpg

 

My edits

 

AS15-91-12383.jpg


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#18 Tom Glenn

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Posted 21 April 2020 - 03:31 AM

This started as simply an Apollo 13 specific thread, but it's turning into more of a general Apollo/Tsiolkovskiy photography thread.  I've taken a look at a few mapping shots of Tsiolkovskiy from Apollo 17, and the difference between the monochrome film, and the color film, is fairly astounding.  Apparently, NASA wasn't initially considering taking any color film to the Moon, but decided to for public relations, which was probably a good move.  But the film grain of the monochrome film is much smaller, and the results are fairly amazing when you look at the full sized images.  This image is from the link below.

 

http://wms.lroc.asu....ame=AS17-M-2798

 

The focal length of the mapping camera was only 76mm and f/4.5.  The camera used 5 inch film (127mm, large format, similar to what Ansel Adams used).  This makes the raw scan 25,000 pixels across.  Interestingly, if you download the raw file (1.2GB), and open with image with a linear color profile, it looks extremely overexposed.  In fact, on a digital camera this exposure would no doubt have been, but the film has wide latitude to protect against overexposure (film is very resistant to full saturation--nonlinear response), and most details can be recovered.  The other available sizes of the image other than raw are already preprocessed, so you don't see this effect.  In the next post is a cropped region, better showing the resolution.  

 

Raw film

 

AS17-M-2798-raw.jpg

 

 

AS17-M-2798.jpg


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#19 Tom Glenn

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Posted 21 April 2020 - 03:32 AM

Note the scale bar in the corner.  This image is still downsized to 25% of the original scan size.  

 

AS17-M-2798-crop.jpg


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#20 DMach

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Posted 21 April 2020 - 10:05 AM

Aside from the resolution, that scale bar also serves to illustrate how big that central peak is!

#21 TOMDEY

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Posted 21 April 2020 - 01:06 PM

Nice information content! I was with B&L and then Kodak at that time. We provided some optics and the custom films in 70mm, 5-inch and 9-inch widths, for Government Programs.  Yes, indeed --- the nonlinearity and tremendous latitude is magnificent, even including "extended latitude" films. They must have put a lot of effort into anticipating best exposure parameters, so the astronauts could just let the cameras run with a minimum of finessing. I would expect (hope?) that Kodak was in on the scanning. Guessing that sensible would be a quick initial scan, followed by meticulous later scans, for the archives --- but now seems that a heck of a lot of ~old~ space-programs data is either lost or so deeply buried in archives that no one seems able to locate it. Things happened very quickly back then. Focus was always on the next mission(s), with little bandwidth reserved for debriefing and archiving.

 

Hard to imagine swinging around Luna's Backside, Radio Silence... hoping for acceptable trans-earth trajectory, enough air, safe landing --- and still grab some good images of the single-pass far side of the moon!     Tom



#22 Tom Glenn

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Posted 21 April 2020 - 08:41 PM

Thanks for the comments Darren and Tom.  Yes, lots of interesting things to discuss.  I'll keep adding more later as I think of things.  I've been enjoying digging into the archives.  I'm not sure how many times the films were scanned, but most of the high resolution scans were make around 2005 it looks like, and were intended to replace some earlier, poorer quality scans.  Whether they are the best possible scans, or if things could be improved now, I have no idea.  

 

More information on the mapping camera is below.  It's impressive to think of the optics required to cover a 5 inch film.  Interestingly, the mapping camera was combined with a laser altimeter, and a stellar camera, all in the same unit.  The stellar camera was used to calibrate the spacecraft location and orientation at the time of each image, and the altimeter determined the distance to the sub-satellite point.  So the field coordinates provided are actually highly accurate, despite the use of old technology, and allowed good maps to be made. 

 

https://history.nasa...ing-camera.html

 

I also noticed something interesting in the raw scan, because it is exposed so highly.  What initially looked like a non-uniformity in the shadows, perhaps from the scan or other issues, is actually showing some detail in the shadows of the mountains.  You can easily see this below, on the shadowed eastern slopes of the mountains.  The only significant source of illumination in these regions would be reflected sunlight from the adjacent terrain (no Earthshine, because this is the far side).  Some of the terrain seems to glow in the dark.  

 

AS17-M-2798-shadows.jpg



#23 Lacaille

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Posted 21 April 2020 - 08:53 PM

Tom this has been fascinating and it is a treat to see your meticulous work, a true homage to those brave men. Do you think this is the first time this has been done with these films?

Mark

#24 wargrafix

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Posted 21 April 2020 - 10:23 PM

Mind is blown.
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#25 Tom Glenn

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Posted 22 April 2020 - 02:29 AM

Thanks for the additional comments, Mark and Wargrafix.  I've had fun with this thread, and I hope that others are also finding some entertainment here.  I particularly enjoy topics that span multiple areas of interest.  In this case, there is much to discuss with regards to history, technology, and data processing, with similarities and differences spanning a period of 50 years. 

 

 

Tom this has been fascinating and it is a treat to see your meticulous work, a true homage to those brave men. Do you think this is the first time this has been done with these films?

Mark

Mark, thanks for the kind words.  Yes, these data have been analyzed at length in the past, although as Tom Dey mentioned, much of the work has become buried in the avalanche of data that has followed in the years since.  Anytime someone revisits an original scan, they bring a potential new interpretation to the old data.  So, while I don't know the extent to which each frame has been analyzed, I do know that these images formed parts of lunar maps, that were the best available in the 1970s.  These maps were then superseded by subsequent mapping missions of the Moon, and the current best maps are from the Lunar Reconnaissance Orbiter (LRO), which is still in a polar orbit around the Moon.  However, there is much interest, at least for me, in looking back at what was done during the Apollo missions.  Also, in some abstract sense, the fact that these missions were manned missions adds an element of intrigue to the data.  

 

For reference, here are some additional links that may be of interest with regards to the mapping camera data.  There is an almost overwhelming array of databases, some of which provide the same data.  Here are some links to maps produced from the Apollo missions.

 

https://www.lpi.usra...og/apolloindex/

 

And in particular, the image of Tsiolkovskiy from Apollo 17 that I posted above formed a part of "Sheet 3" of this map series.

 

https://www.lpi.usra...index/apollo17/

 

Shown below is a low resolution copy of the entire map, and the map legend.  Following in the next post is a crop of the original map, showing the area around Tsiolkovskiy.  The map is an artistic rendering of the photographs, and is only low resolution, but its value is that it provides the locations for individual photographic frames, which can then be analyzed in greater detail.  Some individual frames are marked specifically, and then intervening frames are annotated with a "+" mark on the map, in succession.  For example, you can see that image #2798, which I referenced in the previous post above from Apollo 17, was taken during orbit #74, with the sub-satellite position of the spacecraft nearly overhead the central peak of Tsiolkovskiy, and moving in the northwesterly direction.  The inclination of the Apollo 17 orbit was about 28 degrees, according to the NASA mission report, and in a Mercator projection, the ground path of the satellite follows a gradual sinusoidal curve, which you can appreciate from the full sized maps.  

 

Apollo17-map.jpg

 

Apollo17-map-legend.jpg




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