Service Module Damage: A Photographic AnalysisThis article considers the utilisation of modern image processing and enhancement to determine the impact of the catastrophic failure of Cryogenic Oxygen Tank 2, and it"s subsequent impact on Bay 4 and critical systems on Apollo 13. The analysis also aims to aid visualisation and identify key components of the damaged Service Module.
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Details of the original photographic analysis which formed a significant part of the 1970 investigation can be found in Apollo 13 document collection with particular reference to the following documents:
As in the original 1970 investigation report, there were key images taken by the crew through the window of Lunar Module "Aquarius", shortly after the Service Module separated from the Command Module. These include:
Figure 1. These three images of the jettisoned SM have been derived from the Apollo material above. Image reprocessing: Andy Saunders (Click for the full size version.)
Image A (from 8500) is the most commonly referenced image showing SM damage and is an enhanced crop of the full frame. Further minor enhancement has been made by Andy Saunders to improve clarity and localised contrast.
Image A yields a reasonable level of contrast and detail, particularly in the damaged Bay 4 area. A hint of a dark stain is also visible on the engine nozzle.
Image B (from 16mm film magazine 1151-FF) is, in fact, 8 separate 16mm video frames aligned, stacked, and processed by the author. This is a technique typically utilised in modern digital astrophotography and works on the principle that every image contains signal and noise, but the noise is truly random.
Noise may be caused by the grain structure of the 16mm film medium, in addition to digital noise introduced in the film transfers. By aligning and stacking multiple image samples of the same subject, individual values for each aligned feature in the stack can be averaged out, thus reducing noise whilst maintaining signal. The more sample images, the better the averaging, with the improvement in the signal/noise ratio equal to the square root of the number of stacked images. The stacked image has then undergone some wavelet and post-processing. Credit goes to Stephen Slater for providing high quality scans of the original film.
Image B is a very similar angle to Image A and the stacking process has revealed a surprising amount of detail for hand held 16mm camera footage. This image holds the best colour information of the three images (note the Kapton/Mylar blown loose from Bay 4). Of particular note in this new image however, is the apparent damage to the engine nozzle – more significant than has previously been indicated in the Hasselblad frames.
Image C (8464) is one of 26 similar frames taken in succession by the crew and reveals the most detail within Bay 4 due to optimum illumination/Sun angle. The original Hasselblad transparency has been removed from cold storage and rescanned by Johnson Space Center at 200 pixels/mm and extended bit depth (14-bit A/D). Arizona State University then made the original scan available by way of a 1.3GB TIFF file.
The resultant raw film scan has then been extensively remastered by the author to reveal an exceptional level of detail. The full image has been cropped and rotated to a more familiar orientation.
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Image C is at a more favourable angle to illuminate Bay 4 and highlight the damaged area. The new processed image yields an exceptional level of clarity and detail, with even individual mechanical fixings in the panelling visible and fuel cells prominent.
Figure 3. A cropped image of the Service Module from processed Image C. Image reprocessing: Andy Saunders. (Click for the full size version.)
What remains of Bay 4 is now more visible, the panel of which was blown off due to a pressure build-up caused by the catastrophic failure of cryogenic oxygen tank 2. Where exactly was the explosion that caused the failure of critical systems on Apollo 13? What is still visible in Bay 4 after the failure? Exactly what collateral damage was caused?:
In order to aid visualisation of the damage, two further photographs have been utilised. Pre-flight, close-out photographs of Bay 4 taken at North American Rockwell prior to shipping to KSC have been obtained via San Diego Air and Space Museum:
Figure 4. The upper part of Bay 4 of Apollo 13"s Service Module. This contained the spacecraft"s three fuel cells. (Click for the full size version.)
Figure 5. Bay 4 of Apollo 13"s Service Module. This contained the spacecraft"s oxygen and hydrogen tanks for power generation and breathing air. (Click for the full size version.)
The same images were used in the 1970 investigation, however with modern photo-processing technology the images can be combined and distorted to take account of perspective, overlayed and lined up with key geometric features on the SM body in Image C:
Figure 6. Preflight photos aligned with post-jettison SM picture 8464. Image processing: Andy Saunders. (Click for the full size version.)
Figure 7. Labelled version of above showing key components within Bay 4. (Click for the full size version.)
Gradually reducing the opacity of the pre-flight images now reveals the detail inherent in Image C and the changes caused by the failure of oxygen tank 2: