Question regarding Huygens surface video |
Question regarding Huygens surface video |
Dec 9 2016, 08:29 AM
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#1
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Junior Member Group: Members Posts: 43 Joined: 14-December 12 Member No.: 6784 |
Recently I found a short animation of several of the images taken of the Titan surface by Huygens after it landed:
Link to animation. I see that several objects appear to move in and out of frame, which I have read is attributed to fluffy aerosols kicked up from the surface settling down again. My question is, what is the explanation for the object which appears to move horizontally from left to right? If it is in fact the same object in all 3 frames from frame 11-13, it appears at (x,y) pixel coordinates (74,290), (119,291), and (212,297). Is it something on the lens, drifting to the side perhaps? Because I do not know how this sequence of images has been combined, and whether or not they are chronological or in reverse order, or whether there are missing intermediate frames, I cannot estimate the time that passes during the movement of this small blob. Finally, is there a table somewhere with timestamps of all the Huygens triplets? Regards, Nick |
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Dec 16 2016, 04:36 PM
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#2
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Member Group: Members Posts: 656 Joined: 20-April 05 From: League City, Texas Member No.: 285 |
The Huygens descent imager (DISR) utilized a custom hardware solution to implement jpeg-like compression of the images. Is anyone aware of a software emulator of this compression tool? Or even an equivalent and clearly defined algorithm? I've sketched-out a statistical and simulation approach to attempt to extract additional information about the uncompressed images, but I really need some means of taking a simulated uncompressed image and then compressing it as the Huygens system did. My goal is, following compression, to be able to exactly reproduce the compression artifacts from the side-looking imager produced by DISR.
The closest I've come to an answer is the papers: THE DESCENT IMAGER/SPECTRAL RADIOMETER (DISR) EXPERIMENT ON THE HUYGENS ENTRY PROBE OF TITAN, by Tomasko et al, Space Science Reviews 104:469-551, 2002. https://www.researchgate.net/publication/22..._Probe_of_Titan Comparison of the Lossy Image Data Compressions for the MESU Pathfinder and for the Huygens Titan Probe, by Ruffer et al, NASA, 1994. https://ntrs.nasa.gov/archive/nasa/casi.ntr...19940023751.pdf So far as archived imagery, this resource seems helpful: CASSINI PROJECT, IMAGING SCIENCE SUBSYSTEM (ISS), ARCHIVE VOLUME SOFTWARE INTERFACE SPECIFICATION (SIS) http://pds-imaging.jpl.nasa.gov/documentat...ini_archsis.pdf A concern I have with simply implementing an algorithm is that it likely would not completely account for the hardware limitations of the solution used on Huygens, such as floating point arithmetic with hardware-specific byte limitations. Plus, if I did implement an algorithm I would still want to be able to validate it on a known pair of uncompressed and Huygens-compressed images. |
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Dec 16 2016, 05:02 PM
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#3
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
Comparison of the Lossy Image Data Compressions for the MESU Pathfinder and for the Huygens Titan Probe, by Ruffer et al, NASA, 1994. https://ntrs.nasa.gov/archive/nasa/casi.ntr...19940023751.pdf Based on this reference DSIR used 16x16 DCT blocks and a single quantization value for all coefficients except the DC coefficient, unlike standard JPEG which uses 8x8 blocks and a different Q for each coefficient. The hardware DCT chip datasheet is http://www.littlediode.com/datasheets/pdf/...STV/STV3200.PDF and that describes the bit widths of the internal computation. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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