Rev 56 observations |
Rev 56 observations |
Jan 15 2008, 06:13 PM
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#1
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
I feel a bit like a caretaker sweeping up in the background, what with all this Messenger Mercury activity, but here goes :
The Ciclops looking-ahead detail has been posted for Cassini's Rev 56, disappointingly, no Methone observations are slated (closest we get from here on in) but I'm sure there's a good reason. Interestingly, they list two 'calibration sequences' for the NAC just prior to apoapse when there will be a 'stare' into the (relative) blackness of space to determine camera sensitivity, and any damage to the optics. I presume that this is so that any lens anomalies can be subtracted from subsequent images. Strikes me as good housekeeping what with the lull in Titan observations until 22nd Feb. Ok, as you were, back to my sweeping (GO MESSENGER!!!!) |
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Jan 15 2008, 06:17 PM
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#2
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
I presume that this is so that any lens anomalies can be subtracted from subsequent images. Sounds like dark current characterization to me; seeing how it builds up after prolonged exposure to space environment, characterizing "hot" pixels and such. I always found the term "dark space" interesting, is there really any region in the sky where you wouldn't pick up at least several stars in your FOV if you stared for several seconds? -------------------- |
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Jan 15 2008, 08:05 PM
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#3
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
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Jan 15 2008, 08:22 PM
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#4
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Member Group: Members Posts: 540 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
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Jan 15 2008, 08:46 PM
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#5
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Senior Member Group: Moderator Posts: 3233 Joined: 11-February 04 From: Tucson, AZ Member No.: 23 |
Unfortunately, it is.
-------------------- &@^^!% Jim! I'm a geologist, not a physicist!
The Gish Bar Times - A Blog all about Jupiter's Moon Io |
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Jan 15 2008, 09:13 PM
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#6
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Holder of the two leashes, I share your regret re: Methone, (If only Methone)
Perhaps a privileged insider (Volcanopele, Tallbear?) can shed some light on future possibilities for imaging of this little rock - I understand (based on information on this forum and a couple of similar ones) that Cassini will buzz Methone reasonably closely a handful of times between now and the end of the XM. Ranges vary from ~18,000km to 88,000km between now and the end of 2010. The lower end equates to 25 pixels or so in the NAC FOV - enough to discern some large craters. What are the odds............ |
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Jan 15 2008, 09:36 PM
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#7
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Administrator Group: Admin Posts: 5172 Joined: 4-August 05 From: Pasadena, CA, USA, Earth Member No.: 454 |
Here's the specifics on the closest upcoming encounters with Methone. Most of them are quite high phase, unfortunately; today's was extremely high phase at 142 degrees.
56 2008-015T21:11 Inbound 15517 km flyby, speed = 13.7 km/s, phase = 142 62 2008-083T11:24 Inbound 102556 km flyby, speed = 17.0 km/s, phase = 114 67 2008-130T23:36 Inbound 95865 km flyby, speed = 15.2 km/s, phase = 138 68 2008-138T23:35 Inbound 79224 km flyby, speed = 20.1 km/s, phase = 105 72 2008-168T05:18 Outbound 114262 km flyby, speed = 23.3 km/s, phase = 100 73 2008-175T08:04 Inbound 56806 km flyby, speed = 21.9 km/s, phase = 77 74 2008-182T09:04 Inbound 85994 km flyby, speed = 22.6 km/s, phase = 92 75 2008-189T10:02 Outbound 117044 km flyby, speed = 23.4 km/s, phase = 102 80 2008-224T20:41 Inbound 60489 km flyby, speed = 18.4 km/s, phase = 127 83 2008-247T00:26 Outbound 91222 km flyby, speed = 19.2 km/s, phase = 127 91 2008-305T16:02 Inbound 116146 km flyby, speed = 18.8 km/s, phase = 102 119 2009-287T03:19 Inbound 85902 km flyby, speed = 11.8 km/s, phase = 39 124 2010-011T02:26 Inbound 27175 km flyby, speed = 8.0 km/s, phase = 145 125 2010-027T01:40 Inbound 72123 km flyby, speed = 14.0 km/s, phase = 60 128 2010-079T23:33 Outbound 54797 km flyby, speed = 11.1 km/s, phase = 99 131 2010-138T08:20 Inbound 18453 km flyby, speed = 4.3 km/s, phase = 75 --Emily -------------------- My website - My Patreon - @elakdawalla on Twitter - Please support unmannedspaceflight.com by donating here.
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Jan 15 2008, 10:23 PM
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#8
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Member Group: Members Posts: 540 Joined: 17-November 05 From: Oklahoma Member No.: 557 |
Unfortunately, it is. (Temper tantrum edited out - 2/13) Well, Nereid made it into the Neptune family album with fewer pixels, as did Himalia into Jupiter's (courtesy of Cassini, no less), but this page looks to be blank for Saturn. Just academically, I'm wondering if it would have stayed at high phase (142 degrees) the whole time it was in close proximity. Depending on the orbit, I've seen satellite encounters vary from almost constant phase, to ones that quickly sweep through angles. The programs I use (JPLs Solar System Simulator and Mark Showalters' Saturn Viewer) don't show Methone. |
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Jan 15 2008, 10:27 PM
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#9
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Thanks Em for the clarification. This means that the two remaining Methone closest approaches are:
1) 11th January 2010 - Altitude 27,175, Phase 145 degrees 2) 18th May 2010 - Altitude 18,453, Phase 75 degrees (27 NAC pixels assuming image taken at C/A) The latter is comparable to the best current image of Calypso (31 pixels) and has a good phase angle to highlight topography. Here's hoping that an allowance has been made to image this moon at or near closest approach on that date.
Attached image(s)
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Jan 15 2008, 10:30 PM
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#10
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
You can probably scratch 1) off the list, too, jasedm. That's a really high phase angle.
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Jan 16 2008, 10:48 PM
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#11
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Junior Member Group: Members Posts: 45 Joined: 30-November 05 Member No.: 592 |
The Methone Flyby today occurred over an RSS RING OCC.....
I'm sure that if it had not been sitting right on top of what amounts to what is the highest prioirty Ring Observation that Rings would have found some time for this.... *If there had been an ISS request in the system* but an RSS OCC opportunity trumps anything else around unless we have a series off RSS Occs lined up where we can pick N of M to do. T |
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Jan 16 2008, 10:56 PM
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#12
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Junior Member Group: Members Posts: 45 Joined: 30-November 05 Member No.: 592 |
You can probably scratch 1) off the list, too, jasedm. That's a really high phase angle. Actually .... The phase at C/A is pretty meaningless...... with close flybys we come in practically on an impact course..... so you can have low phase incoming and high phase at C/A and beyond..... and the opposite sometimes occurs but not that often We... and that is several people ... have combed over all the Rock flybys.... particularly the Ring Rocks .... to pick out the most useful flybys.......but I will say that in some circles there is less interest in the non-ring rocks..... but getting good in-close looks at the rocks in and near the rings is a priority ... but it has been a difficult one to achieve.... T |
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Jan 18 2008, 06:49 AM
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#13
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
Tallbear - thanks for the insights. It's interesting to hear about some of the hard decisions that are made as regards trading-off different priority observations.
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Jan 18 2008, 08:16 AM
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#14
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
If Cassini had retained a simple 1-degree of freedom (fore-and-aft) scan platform, a roll maneuver and platform slew could have permitted imaging while the antenna was on Earth for the RSS occultation. Another victim of NASA and JPL's total failure to contain costs during the "Mariner Mark II" development of a new "low cost" multi-mission outer solar system vehicle.
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Jan 18 2008, 09:27 PM
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#15
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Member Group: Members Posts: 655 Joined: 22-January 06 Member No.: 655 |
We... and that is several people ... have combed over all the Rock flybys.... particularly the Ring Rocks .... to pick out the most useful flybys....... T Very interesting T, so can you confirm whether Daphnis and Pan are actually included in future sequences for some close attention from ISS? |
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