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Rosetta flyby of Asteroid Steins, 5th September 2008
tasp
post Jun 25 2008, 05:21 PM
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Thanx for the article!

An idea springs to mind:

How far out from Pluto can New Horizons be and get good light curve data for Nix and Hydra? If we are lucky, perhaps so far out when nothing much else is going on ??

(I just love it when missions can 'cross pollinate' each other)

(If such observations for New Horizons are already scheduled, never mind)


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tty
post Jun 25 2008, 06:57 PM
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Certainly there are earth-crossing binaries. There are several cases of multiple craters of equal age. Steinheim and Ries is the best example, but there are several other more or less certain cases. Even Chicxulub may be linked with Boltysh in Ukraine.
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cosmo
post Jun 29 2008, 10:15 AM
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Around 15% or even more of the NEAs are suspected to be binary. Up to now more than 30 are confirmed out of 5000+ NEAs and most of them are less than 1500m in diameter. It seems the smaller the asteroid the better the chance it is a double.

The YORP effect is maybe the main forming mechanism of binary NEAs as most of them are very tiny. Other more uncommon forming mechanisms are collisions and tidal disruptions due to planetary close-encounter.
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Rakhir
post Jul 3 2008, 09:50 PM
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Rosetta awakes from hibernation for asteroid encounter
http://www.esa.int/esaSC/SEMQPDSHKHF_index_0.html
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charborob
post Jul 4 2008, 02:35 PM
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I've been doing some calculations. Rosetta's narrow angle camera has a field of view of 2,35 x 2,35 degrees. The image size is 2048 x 2048 pixels. At a distance of 800 km, if Steins is about 5 km wide, it will subtend an angle of about 20 arc minutes. At closest approach, Steins' image should then be about 300 pixels wide. That's not much, is it?
For comparison, here's an image of the asteroid Gaspra scaled to 300 pixels wide. That's about what we should expect from the Steins flyby. I didn't take motion blur into account. I don't know if it will be an issue.
Attached Image

If I made some errors, thanks for correcting me.
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tedstryk
post Jul 4 2008, 07:16 PM
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To be fair, Gaspra is a much bigger asteroid - 18.2×10.5×8.9 km - and these are the best Galileo images at their original size. The larger image is a mosaic of two frames, but it just happened that the asteroid was imaged on the edge of the CCD - it could have easily fit in one frame. The smaller image is the next best shot at its original size (it is part of a color sequence). We often see the larger image in greatly enlarged forms and with a false color overlay from infrared data.



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charborob
post Jul 4 2008, 08:49 PM
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In my post, I was just trying to give an idea of what kind of detail we might expect to see on the surface of Stein during the flyby. By the way, the best resolution will be around 16 meters per pixel, if my data on the camera are correct.
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Ken90000
post Jul 7 2008, 08:17 PM
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The Cool thing about 2867 Steins is its type. We have never seen an “E” type asteroid at close range. Unfortunately, as you know, Steins is a tiny asteroid only 4.6 km in diameter.

There would be no point in approaching closer than the planned 800 km. Rosetta simply cannot track a body passing by so quickly. Remember, the spacecraft was designed to explore a comet while slowly orbiting the body.

I look forward to seeing what this body looks like even if the images are only a few hundred pixels across. Likewise, the data from spectrometers and other instruments should keep us occupied until the next flyby.

But, if you are looking for multi-image mosaics, you will have to wait for the 2010 flyby of 21 Lutetia.
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dvandorn
post Jul 8 2008, 04:11 AM
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Let us hope that ESA doesn't do the same thing with Rosetta's Steins images as it did with the crescent Mars images that Rosetta supposedly acquired... *heavy sigh*...

-the other Doug


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ugordan
post Jul 8 2008, 07:29 AM
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QUOTE (dvandorn @ Jul 8 2008, 06:11 AM) *
Let us hope that ESA doesn't do the same thing with Rosetta's Steins images as it did with the crescent Mars images that Rosetta supposedly acquired...

I'm actually willing to let that one pass for them. Reportedly, the images were saturated and not very useful for release so we're probably not missing as much as you think (think CCD charge bleed for example).


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djellison
post Jul 8 2008, 11:45 AM
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Crime 1. Not sequencing a normal RGB sequence during that phase in between the long exposures for dust obs.
Crime 2. Not releasing whatever they did take, either for press release at the time, or via the PDS to date.

But let's not have that debate again - the E2 flyby was quite well 'blogged' - and I expect the Steins flyby will be as well. If I hadn't taken all my time off for Europlanet and IAC - I'd be asking to visit ESOC during the flyby.

Doug
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ugordan
post Jul 8 2008, 11:55 AM
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Crime 2 definitely stands. It's ironic that the comment on the PSA site doesn't even mention OSIRIS data as pending for review, unlike a few of other instruments. I'm keeping my eye on this as no doubt others are, but somehow this doesn't instill confidence we'll be seeing OSIRIS data any time soon.

Second the E2 flyby comment, it was pretty nice. Although, as an imaging kind of person I was left wanting more than 3 images. Not sure if they've been taken at all, though.


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cotopaxi
post Jul 14 2008, 03:36 AM
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QUOTE (jasedm @ Jun 25 2008, 05:21 PM) *
I couldn't find any relevant radar data, but it appears see here that a moon has been likely ruled out for Steins.

Well, it depends on the size of the moon. A moon of a size comparable to that of Steins is probably ruled out, but for example a 100 m sized satellite would create only 1/2500 of the signal from Steins (assuming 5 km diameter for Steins and equal albedo), and that would not be detectable in the Rosetta lightcurve (and I suspect in no other data set).
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tasp
post Jul 14 2008, 12:56 PM
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The article indicates light curve data was taken from 159 million kilometers out!

Seems like looking for opportunities to observe Tempel 1 might be useful. (yes I know it's a comet and light curve data might be harder to interpret)

Are there instruments comparable to OSIRIS on other spacecraft ?

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cotopaxi
post Jul 15 2008, 03:59 AM
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Full quote of previous post removed - mods

OSIRIS observed Tempel 1 for two weeks around Deep Impact. See http://www.esa.int/SPECIALS/Rosetta/SEMUSK5Y3EE_0.html and http://www.esa.int/SPECIALS/Rosetta/SEMSJ06DIAE_0.html

What would we learn from observing Tempel 1 with OSIRIS now?

The High resolution camera on Deep Impact may be comparable with OSIRIS. Bigger telescope on one hand, focus problem and inferior CCD on the other hand. I don't know how SSI on Cassini compares.

Somewhat off topic here: OSIRIS is going to look for the parallax effect in gravitational microlensing in September, after the Steins flyby.
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