EPOXI Mission News Options

[jmknapp]

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.

[tedstryk]

and the resolution around 9 pixels.

Do you mean 9km/pixel? Or the nucleus spanned 9 pixels? Or the coma spanned 9 pixels?

[Paolo]

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?

[stevesliva]

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/

[peter59]

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

[peter59]

Additional observations of comet Hartley 2 from 29 October (fourth row).
http://www.naic.edu/~pradar/103P

[ngunn]

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?

[nprev]

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.

[ngunn]

What is the most likely origin of a contact binary? It could be erosion of an elongated object until the neck breaks.

[siravan]

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).

[hendric]

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.

[Hungry4info]

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

[stewjack]

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

[Astro0]

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

[djellison]

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