Juno perijove 5, March 27, 2017 |
Juno perijove 5, March 27, 2017 |
Mar 16 2017, 10:24 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 |
Juno's perijove 5 is coming up less than two weeks from now - it's on March 27, 2017.
The target selection voting has started and is open until almost four days from now: https://www.missionjuno.swri.edu/junocam/voting?current A large part of the data volume will be reserved for polar time lapse sequences though. John Rogers has written a helpful summary of the upcoming perijove 5: https://www.britastro.org/node/9377 |
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Apr 2 2017, 08:51 AM
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
For completeness, here the statistics resulting from the calibration run:
There are peaks and discontinuities near the change of the s/c spin axis. But at least the camera's optical axis shouldn't change during these maneuvers, with the x-position near 812. The inconsistencies indicate residual flaws in the model, and help to uncover them. |
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Apr 3 2017, 12:10 AM
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IMG to PNG GOD Group: Moderator Posts: 2254 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
For completeness, here the statistics resulting from the calibration run: Have you checked how accurate the interframe delay in the metadata is? For the PJ5 images it is 0.371 but I'm starting to suspect that I might get slightly better results by adjusting it slightly. I haven't tried it yet though but I'm pretty sure any adjustment (if needed) is less than 0.001. Is it possible to discern any rotation in these large storms within the five and a half minutes between images #109 and #110? My best candidate is the large white (anticyclonic) oval A6: Quick back of the envelope calculations seem to suggest this *might* be possible. The elapsed time between the images is ~330 seconds. Assuming a wind speed of ~60 m/s near the A6 spot's periphery (a very crude but probably not bad assumption made by scaling down the speed in the bigger white oval BC in the Voyager era by a factor of ~2 since A6 is smaller) results in a ~20 km movement. This corresponds to roughly 2-3 pixels in the higher-res image which is noticeable if the images are well aligned. That has some super detail in it, including what look like convective cloud elements. Do we know what the pixel resolution is? Considering the context, these convective clouds on the right are in a zone, with overall low altitude clouds, so that we see more into a water rich level. The redder clouds on the left are in a higher belt. It seems the bluer nature of the zone would be consistent with looking through some overlying clear air with attendant Rayleigh scattering. Hmmm... but I have always been under the impression that the whitish zones are higher in the atmosphere than the darker and more reddish/brownish belts and that they are probably ammonia cirrus (the water clouds are much lower in the atmosphere and look darker and more fuzzy). But the possible convective clouds in Roman's image are very interesting. An interesting fact is that these small, whitish clouds are very common and not just in Roman's image. They occur both as isolated features, e.g. at ~(435,740) and in 'clusters', e.g. at ~(980,105) in Roman's image above. And there's a lot of them in the whitish zone. Some of them look like cumulus to me. These clouds seem to occur at various locations although some areas are more likely to have them than others. There are also small/narrow 'elongated', whitish clouds at various locations, typically above darker clouds. I suspect their altitude is similar to the convective/cumulus clouds. Here is an example, an enhanced crop from an image (PJ5 image 110) I'm working on: |
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Apr 3 2017, 03:55 AM
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Member Group: Members Posts: 306 Joined: 4-October 14 Member No.: 7273 |
Hmmm... but I have always been under the impression that the whitish zones are higher in the atmosphere than the darker and more reddish/brownish belts and that they are probably ammonia cirrus (the water clouds are much lower in the atmosphere and look darker and more fuzzy). But the possible convective clouds in Roman's image are very interesting. An interesting fact is that these small, whitish clouds are very common and not just in Roman's image. They occur both as isolated features, e.g. at ~(435,740) and in 'clusters', e.g. at ~(980,105) in Roman's image above. And there's a lot of them in the whitish zone. Some of them look like cumulus to me. These clouds seem to occur at various locations although some areas are more likely to have them than others. It's possible that the white spots are a form of pileus in the ammonia cirrus deck or perhaps even overshooting tops of water vapor cumulus. Given some of the Voyager images you found in a similar region last year, I'm inclined to say it's the latter, but I don't know enough about Jovian meteorology to say if a water vapor-driven updraft is capable of rising that high through the cloud deck without collapsing. This is a good learning experience for me. If we look at this hi-res IR/visible pair we can see most of the hot spots are in the brown belts as you suggest. However some bluish areas continue into the zones with "suppressed" IR warmings. This suggests to me the bluish areas in the zones are areas fairly cold in IR with thin high ammonia haze, while also allowing us a partially transparent view with visible light into much lower altitudes. The equatorward side of the equatorial belts is marked by a vertical jet stream oscillation. You get an IR hotspots where the jet stream is descending and warming the air through adiabatic heating. That clears out the upper cloud decks to give us an unobstructed view deep into Jupiter (probably down to the water cloud layer), which correspond with the dark blue areas in the VIS along the edge of the belt. The ascending portion oscillation generates a long-lived convective updraft that encourages the formation of ammonia cirrus muddied with some of the ammonium sulfate cloud layer that's been carried upwards. Most of that cirrus drifts equatorwards, but some of it gets entrained within the belt circulation patterns and is forming an IR-blocking layer that shows up against the bright IR radiation emitted from the belts. The belts are also a region of generally descending air, so you might also be getting variable IR bright spots where the ammonium sulfate clouds are being eroded more deeply by adiabatic heating. |
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