Voyager mosaics and images of Jupiter, A fresh look at some ancient stuff |
Voyager mosaics and images of Jupiter, A fresh look at some ancient stuff |
Aug 20 2010, 05:47 PM
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Thanks to modern computers and software the old, 'official' Voyager Jupiter images can be reprocessed into something much better. There is also a lot of Voyager data there that was never processed into color composites and/or mosaics (or at least it has not appeared on the WWW). With proper processing the apparent image quality approaches the quality of the Cassini images but needless to say the wavelength coverage is (vastly) inferior.
I have recently been taking a close look at the high resolution Voyager 1 images, i.e. the images obtained in early March 1979. This is going to result in some new and/or reprocessed mosaics. The first one is now complete and I'm working on another one. The image below is a 12 image mosaic (12 orange + 12 violet + 12 synthetic green images). The images were obtained on March 2, 1979 at a range of 4.3 million km. The first image (C1629045.IMQ) was obtained at 05:09:23 and the last one (C1629131.IMQ) at 05:46:11. The resolution is roughly 43 km/pixel. The raw images were calibrated, reprojected to simple cylindrical projection, mosaicked and then rendered using a typical viewing geometry (there is no such thing as a "correct viewing geometry" because the images were obtained over a 37 minute period with Jupiter rotating). I then fixed the color balance. I still haven't 'standardized' how I process the Voyager color. I wasn't completely satisfied with the color I got using an approach similar to what's described in another thread but I think the color could be improved a bit. The final step was to sharpen the resulting image a bit, mainly to compensate for all of the resampling that the previous processing steps required. This image shows lots of features: The Great Red Spot and one of the three white ovals present during the Voyager flybys, smaller spots, scallopped belt/zone boundaries, gravity waves, a bright equatorial plume and the dusky south polar region. I don't think I'm bragging by saying that this is probably the best Voyager 1 Jupiter mosaic that I know of, mainly because of its size (12 images). I will be posting more Jupiter stuff in this thread in the coming days/weeks, both mosaics and interesting images (and needless to say, others are welcome to post images and mosaics as well). |
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May 15 2011, 09:19 PM
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Here is what's probably the final version of the Voyager 1 approach movie that has the GRS at the center of the disk:
jup_8x_30fps.avi ( 1.4MB ) Number of downloads: 987 I posted a very early 16 frame version of this several months a ago but now I'm posting the entire approach movie. The movie is based on 58 orange-green-blue color composites obtained on every Jovian rotation from January 6 to January 29, 1979. Over this period Voyager 1's distance from Jupiter dropped from 58 to 36 million km so the resolution and sharpness of the frames increases from start to finish. This version has been 'tweened' as described by Ian R earlier in the thread. The parameters are slightly different though; I increased the number of frames by a factor of 8 and then changed the frame rate to 30 fps. As described earlier when I posted a very early 16 frame version of this movie, the frames are processed to keep Jupiter's size constant. This is accomplished by reprojecting the source images to simple cylindrical projection and then rendering everything using the same viewing geometry. I also sharpened the images a bit to better reveal various details. Because I didn't have any information on the viewing geometry and camera pointing I had to 'reverse engineer' all of that information. I was unable to do it to perfect accuracy but I still think the resulting geometric parameters are fairly accuarate. Another source of errors is that the images had to be corrected for geometric distortion and that correction probably isn't perfect, especially where Jupiter is close to the edge of a frame (or even partially outside the frame due to bad pointing). These errors manifest themselves as lots of features that appear to 'wobble' a bit and I'm pretty sure that motion is not a real feature. In fact this looks a bit like an earthbased telescopic video of Jupiter except that Jupiter appears very sharp. Some minor but spurious color variations from frame to frame may be apparent. This is because in many cases the source frames had data dropouts and I had to use partially synthetic color. In some cases Jupiter was partially outside the frame due to pointing errors and in one case the pointing was so bad that none of the three images (OGB) could be used. To keep the apparent frame rate constant everywhere I used Sqirlz Morph to generate a totally synthetic frame from the two adjacent frames where this happened. This worked remarkably well and I think it may be almost impossible to spot where I did this. An interesting fact I recently realized is that I have been using a large number of programs/software packages when doing this. I don't know if that's unique to my image processing. In addition to at least six programs and command line utilities written by myself I used these and maybe more (list in no particular order): Photoshop Paintshop VideoMach VirtualDub AviSynth Sqirlz Morph MSU Frame Rate Conversion Filter Excel And also some simple programs that come with Windows, e.g. Calculator and Notepad . Counting everything that's at least 16 programs and command line utilities. |
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