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: 2254 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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Sep 1 2010, 10:21 PM
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IMG to PNG GOD Group: Moderator Posts: 2254 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
A new, big mosaic of Voyager 1 images, this time showing the Great Red Spot at high resolution. The first version has normal brightness and contrast and its overall color should be fairly accurate. Small scale features have been sharpened a bit. In the second one the contrast and sharpness have been greatly exaggerated:
This is a 4x3 mosaic of images. The processing is almost identical to the processing described in the first message of this thread so I'm not decribing it further here. One caveat though: There is probably some slight geometric distortion but it shouldn't be a problem in this case. The images I used were obtained on March 4,1979 at a distance of about 1.85 million km. The first image (C1635314.IMQ) was obtained at 07:08:36 and the last one (C1635400.IMQ) at 07:45:24. The resolution is roughly 18 km/pixel. Mosaics of some of these images have appeared before as 'official' image releases but interestingly, only 3x2 images were used in all cases. The offical mosaic can be seen at http://photojournal.jpl.nasa.gov/catalog/PIA00022 . There is a false color version (lots of blue color) that is better known: http://photography.nationalgeographic.com/...t-103317-sw.jpg My new mosaic reveals an enormous amount of details, especially in the sharpened version. Some of these details I didn't know were visible in any images of Jupiter until relatively recently. The sunlight is coming form the east (right) and because the GRS is in the southern hemisphere it's really coming roughly from the ENE over the GRS and the regions south of it. With this in mind, vertical relief and cloud shadows are clearly visible at many locations around the GRS' periphery. A particularly good example can be seen near (2350,1600) and to the northeast of this location. There is another example near (2480,1080). The wind speeds are especially high there as the elongated appearance of these clouds may suggest. More examples can be seen near (600,980) and (370,920) and (540,1600) and possibly (925,550). These clouds have changed the appearance I imagine Jupiter would have from low altitude (1000 km or something like that). There are also some interesting clouds at (2270,605) and further east. This is the highest resolution color mosaic completely covering the GRS that I have ever seen. Galileo didn't obtain GRS mosaics at this resolution and Cassini passed too far away from Jupiter. This image looks sufficiently different (and better!) from the old, official versions that in a way I feel like I'm processing stuff from a new planetary encounter when I see this. We will probably not be seeing anything comparable to this until EJSM (or some future spacecraft) starts orbiting Jupiter. Hopefully it will be carrying a camera capable of obtaining even higher resolution images than this from the distances it typically images Jupiter at high resolution. Interestingly, the orange and violet images I used here were followed by a green filtered GRS mosaic ~40 minutes later. However, I couldn't used these instead of synthetic green because some of the clouds (especially in the GRS' northeast periphery) move so fast that the three color channels couldn't be properly aligned if I used the green images. |
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