Juno perijoves 2 and 3, October 19 and December 11, 2016 |
Juno perijoves 2 and 3, October 19 and December 11, 2016 |
Oct 26 2016, 04:44 PM
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#1
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Junior Member Group: Members Posts: 22 Joined: 13-October 13 Member No.: 7013 |
A lot has happened and it seemed like a good time to start a new post. We will be staying in 53 day orbits until the project has a full understanding of the risks that may or may not be associated with reducing the orbit period to 14 days per our previous plan.
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Feb 3 2020, 11:48 PM
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#2
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IMG to PNG GOD Group: Moderator Posts: 2250 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
There is also clearly some misalignment far from the limb that can be seen by 'blinking' the red/green/blue channels rapidly in high contrast areas. The misalignment should be smaller. One important issue is that the x (sample) of the optical axis is *not* at the center (i.e. x=824) in the framelets. Depending on how you are creating these images this may be of importance but I'm not sure it's enough to cause all of the misalignment (in particular not the misalignment near the center of your images).
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Feb 4 2020, 10:58 PM
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#3
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Member Group: Members Posts: 406 Joined: 18-September 17 Member No.: 8250 |
... 'blinking' the red/green/blue channels rapidly in high contrast areas. Doh. I should have already been doing this. I've just been looking at bue/red fringing in high contrast areas. Björn, are you using the standard camera model, or have you developed your own? |
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Feb 7 2020, 01:01 AM
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#4
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IMG to PNG GOD Group: Moderator Posts: 2250 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
Björn, are you using the standard camera model, or have you developed your own? This depends on how you define "...using the standard camera model" . I'm using software written by myself for the geometric processing (reprojecting the framelets to a simple cylindrical and/or polar map etc.). However, some of the code is directly based on information/code from the IK kernel, in particular the distort/undistort code, the location of R/G/B on the CCD, the FOV etc.. I'm also using the SPICE toolkit. Works wonderfully now, especially after lots of improvements I did in November and December 2019 (what was supposed to be a minor improvement in early November triggered a flood of new ideas for improving the software, resulting in faster processing, improved/proper flatfielding, a new (?) function for removing limb darkening, better photometric parameters, an empirical model of the skylight illumination near the terminator, easier limb fits etc.). The only issue I'm working on now is the value I need to add to START_TIME. Using a fairly large sample of images it has become absolutely clear that in my case the average value I need to use is lower than the correct value (0.068). The average value I use is close to 0.040 but it varies and is sometimes close to 0.068. This means that something is wrong. This has no visual effect though and is in that sense not a serious problem (in particular there is negligible misalignment between the R/G/B channels or adjacent framelets from the same color channel). I can think of at least three plausible reasons for this (in fact all of them might contribute to the error) and now that I'm almost finished with the PJ24 images (at least for the time being) I plan on taking a detailed look at this issue. |
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Feb 7 2020, 06:55 AM
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#5
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Member Group: Members Posts: 406 Joined: 18-September 17 Member No.: 8250 |
... some of the code is directly based on information/code from the IK kernel, in particular the distort/undistort code, That is what I was I was referring to. I and (I believe) Gerrald have our own distort/undistort code, Kevin (I believe) is using the standard code via ISIS, but I didn't know if you had your own or used the standard code. QUOTE ... in faster processing, improved/proper flatfielding, a new (?) function for removing limb darkening, better photometric parameters, an empirical model of the skylight illumination near the terminator, easier limb fits etc.). Awesome. Wish I had time to do a proper illumination removal model. When you combine multiple images, is there residual brightness variation that needs to be adjusted to eliminate boundaries between images? QUOTE The only issue I'm working on now is the value I need to add to START_TIME. Using a fairly large sample of images it has become absolutely clear that in my case the average value I need to use is lower than the correct value (0.068). The average value I use is close to 0.040 but it varies and is sometimes close to 0.068. Note, the START_TIME_BIAS in juno_junocam_v03.ti is 0.06188 not .0688. My start times (based on limb fit) range from .03 to .08 |
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