Juno PDS data |
Juno PDS data |
Jan 8 2016, 10:15 PM
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#1
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
There is now PDS-format JunoCam cruise and Earth flyby data available; it's been submitted to the PDS, but MSSS has gone ahead and posted it on their website. I've created an index page to it here. Unlike my usual index pages, there aren't any thumbnails because of the odd nature of JunoCam images, with their long skinny shapes and interleaved framelets. I haven't played much with these data because it's a bit beyond my skill -- I look forward to seeing what any of you can do with it.
-------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Sep 6 2017, 12:02 PM
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#2
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
x=814.21 for the optical axis is astonishingly similar to the values I got in subsubsection 4.1.3 of the article of my above post.
Unfortunately, I need to deviate from the best fits derived from star positions in order to obtain best-fits of local RGB alignment, the latter two orders of magnitude more accurate. There must still be some unconsidered effect, at least in my models. I hope, that I'll find more time for geometrical calibration near the end of this year. Possibly K3 plays some role near the margins. And I'm inclined to verify, whether there is some small chromatic aberration, and whether the pixels are perfectly square. |
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Sep 19 2017, 12:38 AM
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#3
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Unfortunately, I need to deviate from the best fits derived from star positions in order to obtain best-fits of local RGB alignment, the latter two orders of magnitude more accurate. There must still be some unconsidered effect, at least in my models. I hope, that I'll find more time for geometrical calibration near the end of this year. Possibly K3 plays some role near the margins. And I'm inclined to verify, whether there is some small chromatic aberration, and whether the pixels are perfectly square. k1 and k2 values that result in more accurate RGB alignment would be very useful. Using the updated radial distortion function parameters (k1 and k2) and focal length from the new JunoCam kernel file has reduced the RGB color alignment errors I'm getting (the updated frame kernel is probably also significant here). After reprojecting the framelets to simple cylindrical projection I usually warp the green and blue channels into the red channel because even an alignment error of just ~2 pixels is noticeable in enhanced/sharpened images - I want 'perfect' alignment. However, when I use the new kernels the alignment errors are smaller than before (I need to process more images to completely confirm this though). The area where I need to warp the GB channels is also smaller (it's near the image edges - close to center the alignment is/was perfect). Some of the alignment errors might be due to slight inaccuracies in the camera pointing parameters I'm using when reprojecting the images. Regarding a possible small chromatic aberration: Is it possible that the best way to get rid of RGB alignment errors might be to use slightly different k1 and k2 values for the different color channels? Has this been tried? |
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Sep 19 2017, 02:34 AM
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#4
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Senior Member Group: Members Posts: 2517 Joined: 13-September 05 Member No.: 497 |
Is it possible that the best way to get rid of RGB alignment errors might be to use slightly different k1 and k2 values for the different color channels? I'd have thought that the focal length would be a larger variable than k1/k2. Gerald has said that he is getting residuals much smaller than 0.1 pixels. I haven't been able to get anything close to that good, so it would be very useful for him to document his processing in a way that could be incorporated into the I kernel. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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Oct 28 2017, 11:42 PM
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#5
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
Gerald has said that he is getting residuals much smaller than 0.1 pixels. I haven't been able to get anything close to that good, so it would be very useful for him to document his processing in a way that could be incorporated into the I kernel. I'm aligning the RGB centroids of a marble movie image according to some convention by adjusting camera parameters. This problem can be statet as an underdetermined system. Therefore it isn't too difficult to find a solution with an error on the order of a few millipixels, much better than it's possible with star streaks. This doesn't mean, that such a local solution needs to apply globally. But it provides a means of obtaining rather accurate data points required for global calibration. Here an intermediate and very technical report, including some analysis of several scenarios: junocam10_geometry_by_single_mm_pj08.pdf ( 1.5MB ) Number of downloads: 984 It's about what I've been able to write up, before I needed to switch tasks. I hope, that I'll find time to continue with global calibration after a first run of PJ09 processing is completed, with an RMS minimization method I've hinted to in the above article. Accurate registering isn't limited to centroids, but determining centroids is rather straightforward to implement. |
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