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Instrument commissioning phase, Beginning final approach to the comet
stone
post Jul 26 2014, 09:21 AM
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If you make a nice film of the rotation put this in a computer model and get from this the center of gravity around which it rotates and from the images the volume at any given distance to the center, would it be possible to calculate the density difference of the comet? For the elongated asteroid Itokawa the MPS scientist did this already.

http://www.mpg.de/7899076/asteroid-Itokawa
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dilo
post Jul 26 2014, 12:04 PM
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Stone/Hungry4info, a simple rotation movie can give only informations on period of rotation and nucleus orientation relative to rotation axis; if you have good reference system (exact knowledge of spacecraft and nucleus positions) you can argue also absolute axis position and orientation, nothing more (at least on short intervals of observation). As you knows, such axis include the center of mass BUT you cannot say where exactly is this point, unless nucleus is subject to multiple rotations (precession).
For Itokawa, if you read article you linked, they argued the density heterogeneity by combining the informations on the shape (from Hayabusa) with Earth-based long-term observation of Yarkovsky effect!


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Zelenyikot
post Jul 26 2014, 12:42 PM
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New images of 67P by Andrei Larin laugh.gif
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0101Morpheus
post Jul 26 2014, 02:49 PM
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Looks like a duck!
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JohnVV
post Jul 26 2014, 04:52 PM
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that is a "Duck" mesh with a normal map
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dilo
post Jul 26 2014, 05:08 PM
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A RUBBER duck! laugh.gif tongue.gif


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machi
post Jul 28 2014, 01:11 PM
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New images from NAVCAM were published.
This is 5 magnified and slightly enhanced image from 27.7. Original resolution (without magnification) was 216 m/pix.
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Gerald
post Jul 28 2014, 01:33 PM
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"Stairs" in the silhouette look like "jiggering" due to lower image quality in comparison to the OSIRIS images thus far. It's probably not real features.
Difficult to do any meaningful subpixel analysis.
But we can at least see, how the comet comes closer.

Edit: Here two strongly enhanced versions starting from the "full" images (no sharpening or hipass filtering used, just magnifying and overall brightness stretching), to mark the high-albedo zone, 26 and 27 July:
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Attached Image

Still not quite free of jpeg artifacts and jiggering, but the bright region looks rather clear.

From this perspective exposed interior material might be another possible option for the presumed high albedo.
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Phil Stooke
post Jul 28 2014, 06:10 PM
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My stretchy version of all three new releases. Maybe that's another bright streak on two of them. Those two (on right) are close to zero phase by the look of it (spacecraft crossing the comet-sun line) so albedo differences show up well.

Phil

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djellison
post Jul 28 2014, 06:40 PM
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I believe their shape file is here : ftp://ssols01.esac.esa.int/pub/data/SPICE...LSSP/LSSP_TEST/
as RS_GLOBAL_DTM_20m.ROS

(edit - that's a very old one - CREATION_DATE = 2014-04-30T18:11:30 )
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JohnVV
post Jul 29 2014, 01:09 AM
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RS_GLOBAL_DTM_20m.ROS
is old
the mesh in Blender


file
"CSHP_DV_031_01_______00017.ROS"
is older
CODE
FILE_TYPE            = SHAPE MODEL
CREATION_DATE        = 2013-11-18T10:00:00
VERSION_NUMBER       = 1
OBJECT_NAME          = CHURYUMOV GERASIMENKO

COMMENT This is the shape model from ESOC
COMMENT comming from simulation test favor826

COMMENT The units in the file are:
COMMENT - km for lengths

COMMENT For the POLYHEDRON model, the following constraints apply:
COMMENT The vertices of a face must be contained in a plane
COMMENT The vertices of a face are given in counter-clockwise order, as seen from outside the body
COMMENT All faces shall define a closed surface


META_START
MODEL_TYPE            = POLYHEDRON
NUMBER_OF_VERTICES    = 13443
NUMBER_OF_FACES       = 26884
META_END

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Gerald
post Jul 29 2014, 01:43 PM
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In the 28 July Navcam image a region within the high albedo region looks particularly bright:
Attached Image

They are working on the shape model.
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anticitizen2
post Jul 29 2014, 01:49 PM
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Exciting!
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tedstryk
post Jul 29 2014, 05:59 PM
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These Navcam views have a superficial resemblance to Vega images of Halley.

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Phil Stooke
post Jul 29 2014, 08:37 PM
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anticitizen2 says: "exciting!"

Yes.. when you see that thing hurtling towards you, all you can do is shout 'duck!'


Phil


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