EPOXI Mission News |
EPOXI Mission News |
Oct 21 2010, 04:23 PM
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#76
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Senior Member Group: Members Posts: 1465 Joined: 9-February 04 From: Columbus OH USA Member No.: 13 |
About the flyby, here is an excerpt from the official encounter schedule (http://epoxi.umd.edu/7press/schedule.shtml): "The cometary nucleus will be resolved ~1 hour out with the spacecraft 45,000 km away from its target. **Closest approach of comet Hartley 2 is expected to occur at ~6:50 am PDT at a distance of 700 km.** [...] The MRI pixel scale at closest approach will be 7 m/pixel, giving a nuclear diameter of ~170 pixels in the highest resolution images." Maybe this calculation works: Counting Hubble as an earth-bound telescope, and taking its resolution to be 0.05 arc-seconds, at closest approach (about 0.12 AU, 18e6 km) and with a nucleus diameter of 1.2 km, the resolution would be at best around 16 pixels. So DI would have to be about 10x further away, or 7000 km to be roughly equal. That's about 10 minutes before closest approach. The Hartley 2 picture actually released on the Hubble site was taken much earlier, on Sept. 25, when the comet was .213 AU away and the resolution around 9 pixels. -------------------- |
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Oct 21 2010, 11:07 PM
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#77
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Interplanetary Dumpster Diver Group: Admin Posts: 4404 Joined: 17-February 04 From: Powell, TN Member No.: 33 |
and the resolution around 9 pixels. Do you mean 9km/pixel? Or the nucleus spanned 9 pixels? Or the coma spanned 9 pixels? -------------------- |
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Oct 27 2010, 05:40 PM
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#78
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
Nature published today a nice summary of the flyby http://www.nature.com/news/2010/101026/full/4671013a.html
Am I the only one intrigued by this story of cyanogen? |
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Oct 27 2010, 05:44 PM
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#79
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Senior Member Group: Members Posts: 1585 Joined: 14-October 05 From: Vermont Member No.: 530 |
Am I the only one intrigued by this story of cyanogen? They published a graph here: http://epoxi.umd.edu/3gallery/20101021_CN.shtml I might as well also link to Emily's post from the presser, since I'm already posting. http://planetary.org/blog/article/00002735/ |
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Oct 29 2010, 05:16 PM
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#80
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Member Group: Members Posts: 568 Joined: 20-April 05 From: Silesia Member No.: 299 |
First look at the shape of a comet Hartley 2 !!! For now from Earth.
Link to Emily's post: http://www.planetary.org/blog/article/00002742/ NASA's link: http://www.nasa.gov/mission_pages/epoxi/epoxi20101028.html -------------------- Free software for planetary science (including Cassini Image Viewer).
http://members.tripod.com/petermasek/marinerall.html |
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Oct 29 2010, 05:44 PM
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#81
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Member Group: Members Posts: 568 Joined: 20-April 05 From: Silesia Member No.: 299 |
Additional observations of comet Hartley 2 from 29 October (fourth row).
http://www.naic.edu/~pradar/103P -------------------- Free software for planetary science (including Cassini Image Viewer).
http://members.tripod.com/petermasek/marinerall.html |
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Oct 29 2010, 08:28 PM
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#82
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
Emily's post on the elongated shape of this and other comets http://www.planetary.org/blog/article/00002742/ started me off wondering if elongated shapes are a particular feature of comet nuclei and why that might be so. Here's what I came up with.
Think of a framed picture with an even width of mount all round. The frame is, proportionately, less elongated than the picture. Reverse the process and it's easy to see that removing uniform layers of material from any slightly irregular object will leave a progressively more flattened and elongated residue. Individual cases can have individual explanations of course but I wonder if, statistically, the shapes of comet nuclei could provide a measure of the amount of material lost and therefore the likely original size of these bodies before they were perturbed into low perihelion orbits? |
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Oct 29 2010, 09:07 PM
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#83
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Merciless Robot Group: Admin Posts: 8784 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Yeah, I was just thinking about that too, coincidentally. Haven't had time to really muse on it, but my first thought was whether comet nuclei like Borrelly & now Hartley-2 are products of mergers of binary objects. Are the rotation axes on both such that they 'tumble end-over-end'? That might be an interesting correlation, if it exists.
-------------------- 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 29 2010, 09:27 PM
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#84
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
What is the most likely origin of a contact binary? It could be erosion of an elongated object until the neck breaks.
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Oct 29 2010, 10:52 PM
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#85
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Member Group: Members Posts: 128 Joined: 10-December 06 From: Atlanta Member No.: 1472 |
Reverse the process and it's easy to see that removing uniform layers of material from any slightly irregular object will leave a progressively more flattened and elongated residue. I think even if you start with a perfect spherical body, the effect of spin axis on insolation results in asymmetrical shapes. If the spin axis is perpendicular to the orbital plane, equitorial regions receive more light and the resulting shape is elongated (ellipsoid). On the other hand, if the spin axis is significantly different from perpendicular, then the summer pole at perihelion receives more light and the end result is a squashed sphere (asymmetrical spheroid). |
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Nov 1 2010, 05:59 PM
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#86
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Director of Galilean Photography Group: Members Posts: 896 Joined: 15-July 04 From: Austin, TX Member No.: 93 |
Are most comets we've visited primordial, or shattered debris from objects deeper in the Kuiper Belt? I think the comets we usually see are broken off chunks of KBO's, with only the very occasional "raw" object. My thought is that debris from a collision is much more likely to be elongated than round due to the types of forces ejecting material away from an object; ie circular and radial forces from the point of impact.
-------------------- Space Enthusiast Richard Hendricks
-- "The engineers, as usual, made a tremendous fuss. Again as usual, they did the job in half the time they had dismissed as being absolutely impossible." --Rescue Party, Arthur C Clarke Mother Nature is the final inspector of all quality. |
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Nov 2 2010, 02:57 PM
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#87
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Senior Member Group: Members Posts: 1441 Joined: 26-July 08 Member No.: 4270 |
Time lapse observations of Hartley 2 from EPOXI showing rotation of the comet as seen in the drection of plume(s).
http://www.youtube.com/watch?v=wMRMHnxBQ8A -------------------- -- Hungry4info (Sirius_Alpha)
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Nov 2 2010, 03:41 PM
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#88
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Member Group: Members Posts: 252 Joined: 5-May 05 From: Mississippi (USA) Member No.: 379 |
NASA TV Coverage of the EPOXI Encounter
The shuttle has it's own TV schedule, but these are also listed on THAT TV schedule! However, if something changes with the shuttle anything might happen. REMEMBER the Encounter is on the (Media Channel) & the Post Encounter is on the (Public Channel) NASA TV Schedule November 4, Thursday 9:30 - 11:30 a.m EST (13:30 GMT) - Live Commentary and Coverage of the EPOXI Spacecraft Close-Up Encounter of Comet Hartley 2 – JPL(Media Channel) 4 p.m. EST (20:00 GMT) - EPOXI Encounter of Comet Hartley 2 Post Encounter News Briefing – JPL (Public Channel) Jack |
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Nov 3 2010, 11:09 PM
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#89
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Senior Member Group: Admin Posts: 3108 Joined: 21-December 05 From: Canberra, Australia Member No.: 615 |
Watch the EPOXI encounter from the spacecraft's perspective through this fantastic, brilliant, wonderful and downright best program EVER - Eyes on the Solar System.
Well somebody had to tell you all it was there |
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Nov 4 2010, 12:14 AM
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#90
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
Be kind, it's still in Beta
But go find the NEAR mission and watch it's orbital phase with Eros.... see the Pioneer 11 flyby of Jupiter, and go 'OMFG' at the Ulysses trajectory There's a million things we're still trying to put into it - chances are any suggestions someone might have, we've already got it on a very very unfunded list of 'love to put in...' - but make suggestions |
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