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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#201
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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 12 2016, 08:12 PM
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#202
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IMG to PNG GOD Group: Moderator Posts: 2254 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Here is one final Voyager mosaic of Jupiter that (probably) finishes the sequence of seven mosaics I posted 4 weeks ago (the last mosaic back then is mosaic 7). It is composed from narrow angle and wide angle Voyager 1 images.
Mosaic 8: Highest resolution pre-Juno Jupiter color data. The full size version is too big too post here, this is an enhanced image at 40% the original size: And here are links to the full size versions (7400 x 5550 pixels): Click here for enhanced full size version Click here for approximately true color/contrast full size version Range: ~650,000 km from Jupiter's center. Resolution of original data: ~6 km/pixel. Juno, corresponding height above Jupiter's cloudtops: ~10,500 km (applies to the Voyager narrow angle data) Less than 8 hours before closest approach Voyager 1 obtained a green and violet filter mosaic with its narrow angle camera (NAC) covering most of the Great Red Spot (GRS) - a total of 28 images. Here the effects of the varying illumination across the mosaic have been removed. At ~6 km/pixel this is the highest resolution pre-Juno color data for Jupiter (all of the higher resolution Voyager images are clear filter images). Lower resolution orange, green and violet images from Voyager 1's wide angle camera (WAC) are also used to show the GRS periphery and surrounding areas. The color in this mosaic was rather difficult to process. The WAC filters are significantly different from the corresponding NAC filters and the left/right edges are not covered by all three WAC filters. There are also some areas in the NAC mosaic where only green or violet was available (especially near the corners of the NAC area). The color is somewhat less accurate there. The white box in the image below shows the area covered by the NAC images. The NAC data has two times higher resolution than the GRS cross mosaic I posted earlier. Interestingly, large parts of this higher resolution mosaic do not show significantly more details than the GRS cross mosaic. It's rather as if that mosaic has simply been enlarged by a factor of two. Many of the cloud features become more fuzzy and the boundaries between dark and bright features do not appear as sharp as they appear at lower resolution. There are some exceptions from this, for example in the GRS's northeast periphery where relatively bright, elongated clouds are visible. These clouds change very rapidly and cast noticeable shadows when the illumination geometry is favorable and the resolution high enough. It would be interesting to see Juno images of the GRS northeast periphery and also of the bright convective feature that frequently appears northwest of the GRS. Two other versions of the NAC data and some of the WAC data have been seen earlier (here and here). Despite this I decided to make my own version of this mosaic because this is the highest resolution pre-Juno Jupiter color data. |
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Sep 12 2016, 09:07 PM
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#203
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Junior Member Group: Members Posts: 54 Joined: 7-July 16 From: Austin, Texas Member No.: 7991 |
here are links to the full size versions (7400 x 5550 pixels) The color in this mosaic was rather difficult to process. The WAC filters are significantly different from the corresponding NAC filters Wow, 41MP! I wish I had a bigger monitor - my laptop is just 1MP or so. I'm constantly amazed at the images Voyager was able to get with its one-shot flybys, and look forward to seeing what Juno is able to get when it comes across the great red spot. I've also come to appreciate how difficult putting together mosaics like this can be, and I didn't even realize the WAC and NAC filters were different. Do you use ISIS to help align and process these, or is it something you've developed? Or are these images flat enough that you can work on them in 2D? If it's a trade secret that's alright, just curious what your process is like. |
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