Data Set Information
DATA_SET_NAME TRI-AXIAL ELLIPSOID MODEL OF COMET WILD 2
DATA_SET_ID SDU-C-NAVCAM-5-WILD2-SHAPE-MODEL-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set presents the basic tri-axial ellipsoid shape model of comet 81P/Wild 2, as derived from the Stardust Navigation camera images that were obtained around the time of closest approach to the comet. Additional details and information about the model can be found in Duxbury et al. J. Geophys. Res., Vol. 109, No. E12, E12S02 10.1029/2004JE002316 (2004) [DUXBURYETAL2004]. On 2 January 2004, the STARDUST spacecraft flew past comet 81P/Wild 2 and took 72 images. In these images, the phase angle started at 70 deg during the approach, dropped to 3 deg near closest approach, and then increased to 110 deg during the departure. Most images were obtained within a range of 2,000 km, with the closest at 237 km. The camera took the images using a broadband filter and a CCD that had an angular resolution of 57 microrad/pixel. These images are archived in the PDS Stardust NAVCAM Data for comet Wild 2 (Data_Set_Name: STARDUST NAVCAM IMAGES OF WILD 2, Data_Set_ID: SDU-C-NAVCAM-2-EDR-WILD2-V1.0) A tri-axial ellipsoid model was fit to the limb and terminator in all the Wild 2 nucleus images. The model was constrained by the fact that the viewing geometry changed by 180 degrees during the encounter and essentially the entire illuminated hemisphere of Wild 2 was viewed in these images (or ~50% of the surface, since there was no noticeable rotation during the few minutes that the images were taken). The axial dimensions determined from the visual fit of the model to the limb and terminator were 1.65 x 2.00 x 2.75 km +/-0.05 km (1 sigma). The illuminated limb is reasonably smooth, with the exception of a few large depressions. It is understood that half of the surface was not illuminated and that these unseen surfaces could deviate from the model derived from the illuminated regions. However the model fit to the terminator, even though quite rough due to topographic variations, does give some evidence that the model probably extrapolates to the unseen part of the nucleus to at least a km or better. A body-fixed coordinate system was established with the shortest axis assumed to be the rotation pole and the longest axis used to define the prime meridian. The posigrade axis is defined to match the corresponding poles determined by Sekanina (2003) [SEKANINA2003] and Farnham and Schleicher (2005) [FARNHAM&SCHLEICH2005]. Author ------ The descriptions in this file were written by Tony Farnham.
DATA_SET_RELEASE_DATE 2004-10-15T00:00:00.000Z
START_TIME 1999-02-07T12:00:00.000Z
STOP_TIME N/A (ongoing)
MISSION_NAME STARDUST
MISSION_START_DATE 1999-02-07T12:00:00.000Z
MISSION_STOP_DATE 2006-01-16T12:00:00.000Z
TARGET_NAME 81P/WILD 2 (1978 A2)
TARGET_TYPE COMET
INSTRUMENT_HOST_ID SDU
INSTRUMENT_NAME NAVIGATION CAMERA
INSTRUMENT_ID NAVCAM
INSTRUMENT_TYPE IMAGING CAMERA
NODE_NAME Small Bodies
ARCHIVE_STATUS SUPERSEDED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : A visual fit was used to match the model to the observations. Uncertainties were estimated by changing the parameters until an overlay of the model clearly deviated from the corresponding images. Estimated errors are 0.05 km in the axial dimensions, and 3 degrees in the angular measurements. Review : This data set was peer reviewed on Oct 15, 2004 and accepted pending a few minor corrections and additions, which have been applied.
CITATION_DESCRIPTION Duxbury, T. and T.L. Farnham, TRI-AXIAL ELLIPSOID MODEL OF COMET WILD 2, SDU-C-NAVCAM-5-WILD2-SHAPE-MODEL-V1.0, NASA Planetary Data System, 2004.
ABSTRACT_TEXT Basic tri-axial ellipsoid shape model of comet 81P/Wild 2, as derived from Navcam images obtained around the time of closest approach to the comet.
PRODUCER_FULL_NAME TOM DUXBURY
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