Data Set Information
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| DATA_SET_NAME |
PLATE SHAPE MODEL OF ASTEROID STEINS V1.0
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| DATA_SET_ID |
RO-A-OSINAC/OSIWAC-5-STEINS-SHAPE-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview : This data set presents the detailed plate shape model of asteroid 2867Steins, as derived from the images that were obtained by the Rosettaspacecraft around the time of its closest approach to the asteroid.Additional information about the model can be found in Jorda et al., Icarus221, 1089, 2012 [JORDAETAL2012]. The Rosetta spacecraft reached its closest approach to Steins on 5 September2008 18:38:20 UT at a distance of 803 km. The Optical, Spectroscopic, andInfrared Remote Imaging System (OSIRIS) instrument (including both the NarrowAngle Camera (NAC) and the Wide Angle Camera (WAC)) obtained body-resolvedimages starting 2 hours before closest approach and continuing until about 2hours after. Unfortunately the NAC stopped operating ~10 minutes beforeclosest approach, when the pixel resolution was ~100 m/pix, but the WACcoverage continued throughout the encounter. Images covered about 60% of thesurface, with spatial scales up to 80 m/pix. The shape model presented here was developed from the combination of severaldifferent techniques: Limb profile fitting of 13 images, with stereo controlpoints, provided the initial constraints on the body's shape.Stereophotoclinometry, using 55 NAC and WAC images, was used to refine thetopography of the areas illuminated and visible in the Rosetta images. Theunseen portions of the surface were constrained using the inversion ofphotometric lightcurves. The orientation of the spin axis, derived as part of the solution, is suchthat the North (positive) pole points to a right ascension of 91 deg and adeclination of -62 deg (J2000) with an uncertainty of 5 deg. (Note that thevalues given in the abstract of [JORDAETAL2012] are incorrect.) The body's coordinate system was defined with the +Z axis in the direction ofthe spin axis and the prime meridian (+X axis) is defined to pass through thecenter of the crater Spinel, located near the equator (see [JORDAETAL2012]).The +Y axis completes the right-hand coordinate system. The body center isnot exactly coincident with its center of gravity, but the offset is withinthe uncertainties derived for the surface positions. PLATE MODEL The model is given in the standard PDS vertex/triangular plate format (seeplate_shape_definition.txt in the documents directory) with dimensions incartesian coordniates. STEINS_CART.WRL - 10242 vertices forming 20480 triangles The data are presented with a VRML wrapper that allows the file to bedisplayed with existing VRML viewers that are freely available (e.g., INSTANTPLAYER, OCTAGA, CORTONA, etc.) Different camera angles have been embedded inthe WRL file to display the nucleus from all of the principal axisdirections, with the 'headlight' illumination. Note that the capabilities ofdifferent viewers and different platforms may limit the ability to utilizesome or all of these options. Look for 'cameras' or 'navigation' items inthe menus for different viewpoints and search the help information forturning headlights on/of, etc. SURFACE DISCONTINUITY The shape model contains a flaw in the surface that produces a notable jumpin elevation around the body. This discontinuity is the seam between the twoportions of the model constrained with the different derivation techniques(stereophotoclinometry and lightcurve analysis). TABLE: Shape Model Characteristics [JORDAETAL2012] Area: 92 +/- 9 km^2 Volume: 76 +/- 11 km^3 Mean radius: 2.70 +/- 0.2 km Volume eq. radius: 2.63 +/- 0.2 km Radius range: 1.91 to 3.62 km Dimensions along the principal axes of inertia: A: (6.83 +/- 0.1) km B: (5.70 +/- 0.1) km C: (4.42 +/- 0.1) km Normalized moments of inertia: A: 2.36, B: 3.00, C: 3.68 km^2 Surface Gravity: 0.08-0.13 cm s^2 (for assumed mean density 1800 kg m^3) Axis orientation: RA: 91 +/- 5 deg Dec: -62 +/- 5 deg Rotation Period: 6.04681 +/- 0.00002 hr Note, because the prime meridian is defined with respect to a feature on thesurface, the X, Y and Z axes are not coincident with the axes of inertia A, Banc C. Author------The descriptions in this file were written by Tony Farnham, based oninformation from [JORDAETAL2012] and discussions with the model creator.
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| DATA_SET_RELEASE_DATE |
2013-05-22T00:00:00.000Z
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| START_TIME |
1965-01-01T12:00:00.000Z
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| STOP_TIME |
N/A (ongoing)
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| MISSION_NAME |
INTERNATIONAL ROSETTA MISSION
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| MISSION_START_DATE |
1995-03-01T12:00:00.000Z
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| MISSION_STOP_DATE |
N/A (ongoing)
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| TARGET_NAME |
2867 STEINS
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| TARGET_TYPE |
ASTEROID
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| INSTRUMENT_HOST_ID |
RO
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| INSTRUMENT_NAME |
OSIRIS - NARROW ANGLE CAMERA
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| INSTRUMENT_ID |
OSINAC
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| INSTRUMENT_TYPE |
FRAME CCD REFLECTING TELESCOPE
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| NODE_NAME |
Small Bodies
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| ARCHIVE_STATUS |
LOCALLY_ARCHIVED
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview : Fits of the 45 control points, distributed around the surface, produced anestimate of 20 m for the mean positional error in the illuminated areas.Lightcurve analysis, which provided the primary constraints on the portionsof the body unseen by Rosetta, were good to within 20% of thestereophotoclinometry technique in regions where both techniques could beapplied. This provides confidence that the unseen portions of the model arevalid. Review :The plate model was reviewed on 5 March 2013.
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| CITATION_DESCRIPTION |
Farnham, T.L., Jorda, L., SHAPE MODEL OF ASTEROID 2867 STEINS, RO-A-OSINAC/OSIWAC-5-STEINS-SHAPE-V1.0, NASA Planetary Data System, 2013.
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| ABSTRACT_TEXT |
Shape model of asteroid 2867 Steins, as derived from the Rosetta images obtained around the time of closest approach.
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| PRODUCER_FULL_NAME |
Tony L. Farnham
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| SEARCH/ACCESS DATA |
SBN Comet Website
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