Juno perijove 8, September 1, 2017 |
Juno perijove 8, September 1, 2017 |
Aug 21 2017, 09:13 PM
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
It's time to open a Perijove-8 thread. Only a little more than two days are left for voting. For this perijove pass, JunoCam is scheduled to use more memory than during any previous perijove pass. Therefore, we have the best conditions to collect a considerable number of images, and images of good quality.
One of my votes went to an image near the equator, in order to give the ops team the opportunity to take a lossless image from very close up. In previous perijoves, these very close ups suffered a bit from lossy compression. This time, we may have one of the rare chances to find out, whether subtle small features are present, but escaped notice due to high compression rates. My other votes are for the subpolar regions with the fascinating FFRs. But I don't make specific recommendations, since I'm hoping for a full latitude coverage in good quality. Besides their science value, such a sequence will be a good basis for a pole to pole animation. I'm also curious, whether we can learn more about the polar regions. These images are scheduled in any case. Besides low TDI images, I'm hoping for some high TDI images in order to get high S/N for the circumpolar storm systems. For Perijove-8, we'll get approach and departure images for a global map. So close to solar conjunction, those are of more interest than in times with good observational conditions from Earth. Unfortunately, during Perijove-9, obtaining a global map will be much harder, if possible at all. And as a special bonus, an image if Io is scheduled for PJ-08. My time for processing these images is very restricted in September. But I'll try to cover the full suite of close-ups as soon as the raws become available, nevertheless. |
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Sep 5 2017, 01:49 PM
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
#113, with some remaining repetitive artifacts, I'll need to work on:
This dark ellipse isn't a processing artifact, but the shadow of a moon: I didn't find out the shadow of which moon. With the "Eyes on Juno" simulation, I ruled out all four Galileans. There are three possible explanations: 1. I made a mistake by using the simulation. 2. The simulation is inaccurate. 3. It's the shadow of Amalthea. Is there anyone here, who is able to find out, which moon cast the shadow? |
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Sep 6 2017, 03:50 PM
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#3
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
What this helped me realize is that the programs I use to generate moon location predictions do not include Amalthea. The big ~7 of Saturn and big 5 of Uranus are pretty standard, but the Jupiter ephemeris programs I use all include the Galileans and nothing else. But I found this one:
https://pds-rings.seti.org And here is the simulated view during the last Juno encounter. Amalthea is dead center. It's the culprit. Also, the smaller moons would not cover the Sun as seen from Jupiter, and therefore wouldn't generate an umbra, only a penumbra. Amalthea doesn't cover it completely, either. The day after the eclipse, someone asked me if there are any other cases of moons that just cover the Sun as seen from their planet, and there are some close candidates, Callisto being the closest, but none (known) so close as the Moon seen from Earth. This also helped me realize that Thebe is pretty big – almost half the size of Amalthea. Metis and Adrastea are much smaller. |
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