'rock' satellite flybys, The next ten weeks |
'rock' satellite flybys, The next ten weeks |
May 16 2008, 06:37 PM
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#1
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Cassini's orbits are now averaging 8-9 days apiece as the end of the prime mission approaches, and according to information posted on this forum, Cassini approaches within 75,000km of various 'rock' satellites EIGHTEEN times in the next ten weeks.
These flybys include the closest remaining encounters with Daphnis, Prometheus, Pandora, Epimetheus, Janus, and Pallene (all of these sub-30,000km). Many close moon-encounters fall during Saturn eclipse, and there are many competing experiments around periapse, but hopefully there will be some planned ISS observations of these small moons at or around closest-approach... |
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May 16 2008, 06:52 PM
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#2
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Senior Member Group: Moderator Posts: 3231 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Just a quick scan: Janus (Jun 30; 59000 km; high phase angle), Pallene (August 19; 43000 km)
-------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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May 16 2008, 07:11 PM
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#3
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Member Group: Members Posts: 207 Joined: 6-March 07 From: houston, texas Member No.: 1828 |
Just a quick scan: Janus (Jun 30; 59000 km; high phase angle), Pallene (August 19; 43000 km) there is a sub-5000 km flyby of helene during extended mission, but i ve not yet found when! cheers paul -------------------- Dr. Paul Schenk, Lunar and Planetary Institute, Houston TX
http://stereomoons.blogspot.com; http://www.youtube.com/galsat400; http://www.lpi.usra.edu/science/schenk/ |
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May 16 2008, 07:57 PM
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#4
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Senior Member Group: Moderator Posts: 3231 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
It is on March 3, 2010 at 13:40:41UTC. Distance to Helene's surface is 1803.1 km.
-------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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May 18 2008, 02:18 PM
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#5
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Some long range images (around 350,000km ) of Janus have just been posted example here
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Jul 15 2008, 03:43 PM
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#6
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
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Jul 23 2008, 12:14 PM
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#7
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
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Jul 23 2008, 02:18 PM
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#8
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Senior Member Group: Members Posts: 2173 Joined: 28-December 04 From: Florida, USA Member No.: 132 |
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Jul 23 2008, 02:22 PM
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#9
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Senior Member Group: Moderator Posts: 2785 Joined: 10-November 06 From: Pasadena, CA Member No.: 1345 |
I can't think of a single image which demonstrates gravity better than this Forgive my really naive question: How do we know it's not due to electrostatics? -------------------- Some higher resolution images available at my photostream: http://www.flickr.com/photos/31678681@N07/
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Jul 23 2008, 03:37 PM
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#10
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Forgive my really naive question: How do we know it's not due to electrostatics? Perhaps both processes are visible here. I've read that the outer elements of the F-ring appear to be smoke-sized particles, in which case I wouldn't be surprised if the passing 'wake' of the moon stirred up some of the 'smoke' creating visible ripples, but the 'core' of the ring (the two brighter threads in the image) are made up of much larger constituents, and the obvious kink is surely gravitationally-produced... Just for context, this image was taken from below the ring plane, with Prometheus further from Cassini (by 800km or so) than the core of the ring. |
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Jul 23 2008, 07:40 PM
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#11
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Junior Member Group: Members Posts: 47 Joined: 27-June 08 From: Ashford, Kent, United Kingdom. Member No.: 4244 |
Hi everyone,
Think you may like this one. I'm surprised by the very high calibre of the membership here, this has been missed. Janus in eclipse in Saturn's shadow, lit by the other moons from 33,000 KM. I have cropped, slightly enlarged it & brightened / contrast enhanced the image, as the original was very dark. I'm afraid that I could do nothing about the cosmic ray / noise speckling. Andrew Brown. -------------------- "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.
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Jul 23 2008, 08:35 PM
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#12
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Hi Andrew, this is a view of Janus I've been looking forward to. I agree about the calibre of contributors here. Some of the very best image-smiths showcase their work on this site for all to enjoy.
This image though is Janus in sunlight just prior to eclipse - any image obtained by light due to Saturnshine would have been significantly degraded in terms of quality, and I don't think that there is enough light bouncing off adjacent moons to register in Cassini's optics during eclipse. (see versions of Helene posted in this section) My own attempts to clean up this image owe more to artistic interpretation than anything else, and fall well short of standards here, so i've avoided posting them - I need some practice.... |
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Jul 23 2008, 08:47 PM
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#13
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Senior Member Group: Moderator Posts: 3231 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
It wasn't missed, just covered in a different thread: http://www.unmannedspaceflight.com/index.p...st&p=119744
the increased noise is due to an increase in radiation levels in the region between Mimas and Janus/Epimetheus, not due to low light conditions. -------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Jul 23 2008, 09:22 PM
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#14
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Junior Member Group: Members Posts: 47 Joined: 27-June 08 From: Ashford, Kent, United Kingdom. Member No.: 4244 |
Thanks VP for setting me straight. I was aware of the Janus eclipse, & thought as the original image was so dark, that was taken during said eclipse, not just before.
I see your enhancement, considerably better than mine. I assume the G Ring is responsible for the trapped radiation? I'm not as familiar with the Saturn system as I am of the Jupiter system. Once again, thanks VP & its great talking to you again. Hi jasedm, I'm aware of the Enceladus eclipse imagery a while back, faintly lit by Rhea, Dione & Tethys, with Cassini taking a longer exposure, but being further away with a much larger target, it seems to work. Janus is small & close in to Saturn, so yes that would probably not work thinking about it more logically. Andrew Brown. -------------------- "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.
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Jul 23 2008, 09:26 PM
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#15
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
I was aware of the Janus eclipse, & thought as the inmage was so dark, that was taken during said eclipse, not just before. The image is dark because all the heavy radiation hits confused the automatic contrast stretch algorithm applied on the raws. It saw those high brightness pixels and thought it didn't need to brighten the image any more. In other words, this is closer to the actual 'raw' image downloaded from the spacecraft. -------------------- |
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