Mars Comet Encounter Observations, C/2013 A1 Siding Spring, 19 Oct 2014 |
Mars Comet Encounter Observations, C/2013 A1 Siding Spring, 19 Oct 2014 |
Oct 19 2014, 12:17 PM
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#46
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Senior Member Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 |
I think the sol 782 images taken around 4:08am, elevation 70 degrees, azimuth 100 degrees are the ones with SS in frame, if visible, e.g.,
http://mars.jpl.nasa.gov/msl-raw-images/ms...149C00_DXXX.jpg http://mars.jpl.nasa.gov/msl-raw-images/ms...148C00_DXXX.jpg http://mars.jpl.nasa.gov/msl-raw-images/ms...344C00_DXXX.jpg Based on the ML shots, seems there was quite a bit of sky brightness in the east around 4:10am, a little over an hour before sunrise: http://curiosityrover.com/synth/?camera=ML&station=246 -------------------- |
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Oct 19 2014, 12:46 PM
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#47
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
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Oct 19 2014, 12:59 PM
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#48
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Senior Member Group: Moderator Posts: 3431 Joined: 11-August 04 From: USA Member No.: 98 |
The shape of the comet begins to become more apparent. Uh... no. That's got to be just pre-dawn illumination of the sky. Those pictures have been on the ground over 24 hours. If that were the comet, that image would right now be plastered all over media around the world. |
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Oct 19 2014, 04:02 PM
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#49
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Junior Member Group: Members Posts: 64 Joined: 15-June 12 From: Hong Kong Member No.: 6419 |
Sorry if I sounds like an orbital mechanics rookie, but what are the closest approach distances of the 5 Mars orbiters to the comet?
-------------------- UMSF - the place of Opportunity to satisfy your Spirit of Curiosity via Perseverance
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Oct 19 2014, 04:36 PM
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#50
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Member Group: Members Posts: 102 Joined: 29-January 10 From: Poland Member No.: 5205 |
Sorry if I sounds like an orbital mechanics rookie, but what are the closest approach distances of the 5 Mars orbiters to the comet? comet - MOM - 88 222 km at 18:14 UTC comet - MRO - 135 750 km at 18:28 UTC comet - MEX - 136 890 km at 18:26 UTC comet - Odyssey - 141 140 km at 18:26 UTC comet - MAVEN - 143 290 km at 18:26 UTC -------------------- Adam Hurcewicz from Poland
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Oct 19 2014, 08:10 PM
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#51
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Martian Photographer Group: Members Posts: 352 Joined: 3-March 05 Member No.: 183 |
As Joe said, the comet was up at 70 deg when the twilight images happened. The sky was brighter than any comet has ever been at 1.5 AU from the Sun.
The latest predictions (i.e., what I see in Starry Night - 2 magnitudes, per http://cometcampaign.org/current-status) suggest the comet may total 100X as bright as M31, outside of twilight, at a time when its coma has >5X the angular extent: so the light is diluted to <20X M31. If you've seen previous attempts to image M31 (here and here) in less dusty conditions, then you have an appropriate sense of how bright the comet may appear. Opportunity's night is done, but it is a long wait for a relay pass. Curiosity should get to work soon, but again it will be a long wait. |
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Oct 19 2014, 08:18 PM
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#52
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Thanks very much for the update, Deimos.
I've seen unconfirmed reports that the coma is greater in extent than anticipated (though no means for determining that was specified; presuming it was via Earth-based telescopes, but I'd think that the glare from Mars would complicate that). Does anyone have any reliable information regarding this, or anything else of interest for that matter? EDIT: Found a NASA site for US orbiter status post-passage. Not particularly informative at the moment; all statuses are 'pending'. -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Oct 19 2014, 08:26 PM
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#53
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Senior Member Group: Members Posts: 1621 Joined: 5-March 05 From: Boulder, CO Member No.: 184 |
Just to shuffle these numbers a bit, current magnitude would be about 11.5 from Earth, translating to -4.7 from Mars at closest approach. If M31 is 3.5 magnitude, then SS is about 2000 times as bright. If SS has 5 times the angular diameter as M31, then the areal extent is 25x. Thus the surface brightness would be 80x that of M31.
Seen from Earth, an image 8hrs before closest approach from comets-ml is here where it looks pretty well condensed in an area smaller than 1 arcminute, with the overall coma being around 1 arcminute: http://www.dpreview.com/galleries/45945840...?inalbum=comets Via Twitter today is this pretty neat color image: http://cf.tzecmaun.org/2014/10/mars-and-co...-siding-spring/ An Oct 17th visual description is here: https://groups.yahoo.com/neo/groups/CometOb...ons/topics/5852 -------------------- Steve [ my home page and planetary maps page ]
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Oct 19 2014, 08:50 PM
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#54
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Senior Member Group: Members Posts: 4246 Joined: 17-January 05 Member No.: 152 |
Opportunity also imaged Pi Ceti during a test run a few sols ago. In addition to increased extinction, the distant dust storms make for an annoyingly bright twilight. Thanks for identifying the field. This image shows the stars I identified in the two frames: http://mars.nasa.gov/mer/gallery/all/1/p/3...YOP2664L1M1.JPG http://mars.nasa.gov/mer/gallery/all/1/p/3...YOP2664L1M1.JPG Noise subtraction doesn't help very much with these frames, probably due to the high sky brightness. But it's pretty easy to ID the stars by flipping between the two frames and matching the faint streaks in the longer exposure with the points in the shorter exposure. Here's the result, with identified stars circled: I've superimposed a star map, slightly shifted to the right, so you can see that the identifications are good. There's nothing unexpected here, except the uppermost circled point, which I'm guessing is a star just below the magnitude limit of my map (though someone should check this). It would be nice to know the location of SS when these images were taken, though... On the (slightly) plus side, tau was 1.19 on 3812, when these images were taken. The latest values are slightly better, 1.07 for 3815. Edit: The faintest identifiable stars in my image are about 6th magnitude, at least in the darker part of the frame. |
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Oct 19 2014, 08:58 PM
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#55
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Senior Member Group: Members Posts: 2073 Joined: 13-February 10 From: Ontario Member No.: 5221 |
According to DSN Now everything went well Maven, MRO, Mars Express, and Odyssey. Communications going on just fine...
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Oct 19 2014, 09:14 PM
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#56
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
As expected. It'll be interesting to see if there have been any effects at all on any of the spacecraft.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Oct 19 2014, 10:04 PM
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#57
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Senior Member Group: Members Posts: 2346 Joined: 7-December 12 Member No.: 6780 |
There's nothing unexpected here, except the uppermost circled point, which I'm guessing is a star just below the magnitude limit of my map (though someone should check this)... That's probably the variable star Z Eri, mag. 6.79, according to Redshift 7 software, as far as this can be said for variable stars. |
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Oct 19 2014, 10:41 PM
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#58
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Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Now reporting MRO's fine & successfully maneuvered for all planned observations.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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Oct 19 2014, 11:43 PM
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#59
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Member Group: Members Posts: 890 Joined: 18-November 08 Member No.: 4489 |
QUOTE Noise subtraction doesn't help very much with these frames, probably due to the high sky brightness for image http://mars.nasa.gov/mer/gallery/all/1/p/3...YOP2664L1M1.JPG and image http://mars.nasa.gov/mer/gallery/all/1/p/3...YOP2664L1M1.JPG [attachment=34022:386EFFCH...2664L1M1.jpg] [attachment=34023:4406EFFC...2664L1M1.jpg] |
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Oct 20 2014, 12:16 AM
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#60
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Senior Member Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 |
It would be nice to know the location of SS when these images were taken, though... I get RA 02:44:15, dec -15.25 for SS at the time of those images--can you place it on your diagram from that? -------------------- |
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