EPOXI Mission News Options

[stevesliva]

Looks like the Deep Impact list has been revived. Posting here for others to get back on board:

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EPOXI E-News #1 May 2008
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WELCOME BACK!

Did you know that the Deep Impact Flyby Spacecraft has a new assignment? The
EPOXI mission combines two exciting science investigations in an entirely
new mission that re-uses the Deep Impact spacecraft. The Extrasolar Planet
Observation and Characterization (EPOCh) investigation will observe stars
that have known transiting giant planets. The Deep Impact Extended
Investigation (DIXI) of comets observes comet 103P/Hartley 2 during a close
flyby in October 2010.

The education and public outreach team decided to get back in touch with our
Deep Impact friends and begin sending out newsletters again to keep you
informed of these two exciting investigations! During the two years since
our last newsletter for Deep Impact, the science team has stayed busy
continuing to do more analysis on the data collected in July 2005. The
science team also proposed and was awarded an extended mission teaming up
with a group from Goddard Space Flight Center.
EPOXI website: http://epoxi.umd.edu/
Mission Overview: http://epoxi.umd.edu/1mission/index.shtml
Press Releases: http://epoxi.umd.edu/7press/index.shtml
DI Results: http://deepimpact.umd.edu/results/

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MISSION STATUS

Dr. Deming, Principal Investigator (PI) for the EPOCh portion of the
mission, sends us the latest mission status report in which he tells us
about the current observing target GJ436. “This is an exciting time for
EPOCh, as we search for an exo-Earth orbiting a stellar neighbor of our
Sun!” reports Dr Deming. He also talks about the plans to observe a very
special planet in late May and early June.

Read his status report as well as past reports from other team members at
http://epoxi.umd.edu/1mission/status.shtml

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EPOCh TARGETS

The EPOCh component of the EPOXI mission will carefully study a small number
of stars in order to learn more about planets that we know are orbiting
those stars by watching the planets as they transit (cross in front of) the
star. EPOCh will also search for clues to other planets that might be
orbiting the same stars.

Read more about the EPOCh science targets to find out which stars are being
observed.
http://epoxi.umd.edu/2science/targets.shtml

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PLANET QUEST

Are we alone?
For centuries, human beings have pondered this question. Medieval scholars
speculated that other worlds must exist and that some would harbor other
forms of life. In our time, advances in science and technology have brought
us to the threshold of finding an answer to this timeless question.
The recent discovery of numerous planets around stars other than the sun
confirms that our solar system is not unique. Indeed, these "exoplanets"
appear to be common in our galactic neighborhood.
The EPOCh investigation is part of a larger family of missions studying
extrasolar planets. Learn more at the Jet Propulsion Lab Planet Quest Web site.
http://planetquest.jpl.nasa.gov/index.cfm

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OBSERVING CHALLENGE

The transits that will be studied for EPOCh are extremely difficult to
observe because the change in brightness is very small and requires high
precision photometry that can be accomplished with instruments on the Deep
Impact spacecraft. Observers on Earth can still take a look at the stars in
the night time sky. The selected stars are also pretty dim because we don’t
want them to saturate or over expose the spacecraft instruments but they are
bright enough to be visible in amateur telescopes if the sky conditions are
good and the skies are dark.

Like people, stars have multiple identifiers. EPOCh’s first target was a
star labeled as HAT-P-4 by the scientists observing it. They made their own
list of target stars so that was their shorthand name. But HAT-P-4 has
numerous other names which are more useful in identifying it in other databases.
HAT-P-4 = SAO 64638 = TYC 2569-1599-1 is a magnitude 11, G-class star
located in the constellation Boötes.
Chart: http://epoxi.umd.edu/2science/challenge.shtml

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SUBSCRIPTION INFORMATION

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subscribers may join the EPOXI Mission e-news mailing list on our website
at: http://epoxi.umd.edu/6outreach/newsletter.shtml

[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