30th Anniversary of the Voyager 1 Flyby of Jupiter |
30th Anniversary of the Voyager 1 Flyby of Jupiter |
Mar 5 2009, 08:20 PM
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#1
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Today marks the 30th anniversary of Voyager 1's flyby of Jupiter. On March 5, 1979, Voyager 1 flew through the Jupiter system providing a wealth of information of Jupiter, its magnetic field, and moons. Thanks to Voyager 1, the Galilean satellites became worlds with real geology and amazing vistas. Voyager 1 also revealed Jupiter's ring system and Io's volcanism for the first time.
I've written up a longer post about the encounter with Io on my blog, which also has an animation of the flyby: http://gishbar.blogspot.com/2009/03/30th-a...1-flyby-of.html -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Mar 21 2010, 04:08 PM
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#61
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
Thanks!
What a pity, that most images from Voyager 1 are badly smeared. It's interesting how good work engineers made in other flybys (especially Uranus and Neptune flybys). -------------------- |
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Mar 21 2010, 05:40 PM
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#62
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
I am thinking the color Voyager pictures must have an additional complication over those shot on subsequent missions with solid state imaging devices.
With the vidicon technology they had in the seventies, the actual size of the pixels across the image varies slightly with brightness (due to complex technical reasons in how the electron beam pics off the accumulated charges) and for an object that was noticeably colorful, each filtered picture in the mosaic would have, in addition to varying pixel size from the images being taken at slightly different distances, and pixels slightly askew due to object rotation and motion and the spacecraft flight path diverging from a straight line during imaging, pixels of different size across each image itself. That this can all be allowed for in the processing is amazing, especially in regards to maintaining the very fine detail in each image as we so often see here at UMSF. It would seem that each pixel in the final product might have had some influence from up to 9 pixels in the raw data. If there is a quick and digestible short version of how the image processing can do this (that Callisto pic is truly amazing!!) I think it would be interesting to know. Have any cameras been flown that do some/all of this processing as the images are taken, or is this something the compression software sometimes used does in the course of doing what it does ? |
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Mar 21 2010, 06:08 PM
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#63
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Lord Of The Uranian Rings Group: Members Posts: 798 Joined: 18-July 05 From: Plymouth, UK Member No.: 437 |
That is just a beautiful example of image processing you've achieved there Machi. Nice one!
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Mar 22 2010, 10:13 AM
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#64
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
Thanks!
Tasp: If my memory is right, so different pixels size because of brightness isn't such problem. But vidicon cameras have always bigger geometrical distorsion than CCD cameras. Especially in corners. But CCD cameras also have faults, for example bleeding. And yes, what you said about difficulties with color processing, all is true. Same problem is with Cassini or Galileo images, but in this case, images are taken more quickly and in lower flyby velocities, so changes aren't so prominent. I overcome these problems in different ways. Actually most easy way (and case of this Callisto image) is using wide angle images. Then color information has much lower resolution (in this case 8×). It's no problem with detail preservation. In some graphics programs you can combine two images in such way, that you have full details from BW image and color information from color image (ImageJ, PaintShop Pro). Or you can use narrow angle images taken with different filters, but these were taken only at beginning of flybys. Color information in these images has higher resolution, but it's difficult to remove differences between them. Then you can remapping all images on sphere or apply warping techniques. Another way is using color maps from another missions or different part of the same mission (for example Jupiter's combined LORRI + HST images). Last resort is color from photometry. This is badly usefull in some cases (Io, Jupiter, Earth), but usable in others (Uranus moons, asteroids etc.). Last question: Actually I don't know about scientific framing cameras with this processing. But monitoring camera on Mars Express is actually color camera with multicolor CCD (with Bayer pattern). And we have multicolor push-broom imagers with linear CCD's like HRSC, HiRISE or MVIC (functioning in same way as PC scanner). -------------------- |
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Jul 24 2010, 06:48 PM
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#65
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
I've been experimenting with CIE XYZ colorspace calculations recently with various spacecraft data. This is the same approach I use with Cassini VIMS to generate color, except with camera filters you get many fewer wavelength datapoints so the end result is less accurate. I currently just linearly interpolate the spectral curve between missing points, but it still works pretty well.
As official Voyager images of Jupiter are known to be all kinds of funky colors ranging from greenish, to deeply red I decided to give it a whack. Unfortunately, I don't know how to properly calibrate Voyager images (if anyone has any pointers I'd be glad to hear) so I used raw images off the shelf. The images are c1524909.imq, c1524907.imq and c1524905.imq, OGB frames. Here's a crop of what the straight-up substitution for RGB image channels looks like: Notice the uncalibrated dark current/bias in the upper left corner, also some color shifting near Europa. The colors are similar to some Photojournal images (albeit they are at a higher contrast stretch) suggesting I at least got the relative channel brightnesses right. Here's the image passed through the code that compensates for the differing wavelengths, and cleaned up in Photoshop: Compare to a Cassini image processed the same way: -------------------- |
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Jul 24 2010, 08:37 PM
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#66
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
The cleaned up/color compensated version looks great. The color in many of the ancient, 'official' color images is really bad and they really need to be reprocessed.
I've been experimenting with CIE XYZ colorspace calculations recently with various spacecraft data. This is the same approach I use with Cassini VIMS to generate color, except with camera filters you get many fewer wavelength datapoints so the end result is less accurate. I currently just linearly interpolate the spectral curve between missing points, but it still works pretty well. As official Voyager images of Jupiter are known to be all kinds of funky colors ranging from greenish, to deeply red I decided to give it a whack. Unfortunately, I don't know how to properly calibrate Voyager images (if anyone has any pointers I'd be glad to hear) I really found out 'by accident' how to calibrate Voyager images several years ago: I installed ISIS and following that I suddenly had the Voyager calibration files. I then used information from these files (and possibly some of ISIS' source code - I don't remember) to incorparate Voayger calibration into my software. To simplify things I converted most of the calibration files (flatfields etc.) to 800x800 'raw files' containing 4 byte floating point numbers. By the way - wasn't there a thread somewhere describing in detail the approach you used for generating Cassini (VIMS) color images? I'm just starting a major Voyager image processing project of mine and I'm currently deciding exactly how to process the color images. I might use a similar approach for the first time. |
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Jul 24 2010, 08:57 PM
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#67
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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 are two files containing some information (in particular, voylin.sav contains the equation for the non-linearity correction):
voycal.zip ( 3.87K ) Number of downloads: 391 voylin.zip ( 1.84K ) Number of downloads: 374 As can be seen from voycal.sav there lots of files are needed for calibrating the Voyager images. And a link just to be on the safe side: http://isis.astrogeology.usgs.gov/document...UserRights.html |
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Jul 24 2010, 09:09 PM
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#68
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Thanks for those files, Bjorn. I'll have to give calibration a shot one of these days. The VIMS thread you're probably thinking of is this old one.
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Jul 25 2010, 08:12 PM
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#69
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
This is certainly extremely interesting. I tried recomputing the color balance of a Voyager 2 GRS mosaic I did back in 2001 ago but I now used calculations similar to those used above by Gordan and described in more detail in the VIMS thread. I think the color is significantly more realistic in the new version but beware that there might still be some bugs in my code so this might change slightly. Anyway, this is what it now looks like:
A smaller image showing the color in the old version of the mosaic: The new version definitely looks more realistic in my opinion. It should be noted that I haven't done any gamma corrections. By the way these are images of the Great Red Spot obtained by Voyager 2 on 6 July 1979 at a range of 3.8 million km. We are viewing the GRS from directly above in this mosaic so it shows the GRS' true shape better than the original images which were obtained with the spacecraft about 5 degrees north of the equatorial plane. |
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Jul 26 2010, 08:35 AM
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Lord Of The Uranian Rings Group: Members Posts: 798 Joined: 18-July 05 From: Plymouth, UK Member No.: 437 |
As so often happens, Bjorn and Gordan, your work has yet again inspired me to crack out Paint Shop Pro and have a fiddle with some of the raw data.
Here's a relatively un-scientifically adjusted view of the GRS, taken by Voyager 2 (30th June 1979): -------------------- |
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Jul 26 2010, 11:52 AM
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#71
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Lord Of The Uranian Rings Group: Members Posts: 798 Joined: 18-July 05 From: Plymouth, UK Member No.: 437 |
Here's another view from Voyager 2, taken on May 28th, 1979:
I've used a rudimentary 'recipe' to reach this result, using the three filtered images: Orange, Green and Violet: CODE ORANGE == Add Violet, Dodge 4% GREEN == Add Violet, 48% VIOLET == Add Orange, Negative, Burn 14% Grey World Color Balance Curves adjustment -------------------- |
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Jul 26 2010, 12:03 PM
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#72
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Lord Of The Uranian Rings Group: Members Posts: 798 Joined: 18-July 05 From: Plymouth, UK Member No.: 437 |
Now, this certainly would be a mammoth undertaking, but just imagine what a cleaned-up and properly processed version of this movie would look like:
http://www.youtube.com/watch?v=BosvP4CLz9o -------------------- |
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Jul 26 2010, 02:26 PM
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#73
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The Poet Dude Group: Moderator Posts: 5551 Joined: 15-March 04 From: Kendal, Cumbria, UK Member No.: 60 |
*****y hell...!!!
That's like having a whole new mission to Jupiter!!! -------------------- |
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Jul 26 2010, 04:09 PM
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#74
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
Ah nostalgia. as I watch this I can almost smell the smoldering celluloid fragments inside the whirring projector as someone in the corner mutters, "Hey, pull the curtains closed tighter!"
-------------------- If Occam had heard my theory, things would be very different now.
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Jul 26 2010, 06:48 PM
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#75
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
Ian, Bjorn, Ugordan: Very nice images! Very provocative
Jupiter movie: I was trying this, but it's work for weeks -------------------- |
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