Data Set Overview : This data set presents the detailed plate shape model of comet9P/Tempel 1, as derived from the images of the comet that wereobtained by the Deep Impact spacecraft around the time of closestapproach. Additional information about the model can be found inThomas et al., 'The Shape, Topography and Geology of Tempel 1 fromDeep Impact Observations', Submitted to Icarus, 2007 [THOMASETAL2007] The Deep Impact (DI) spacecraft consists of two parts, an impactor anda flyby spacecraft, that encountered comet 9P/Tempel 1 on July 4,2005. During this encounter, the impactor collided with the nucleusto produce a crater and expose sub-surface material that could beobserved by the flyby spacecraft. During the final approach to the nucleus, three cameras, the HighResolution Instrument (HRI), the Medium Resolution Instrument (MRI)and the Impactor Targeting System (ITS) obtained hundreds of images ofthe nucleus. After the impact, in which the ITS was destroyed, theMRI and HRI continued to image the nucleus for 800 seconds, until thespacecraft entered shield mode and stopped tracking the nucleus.While in shield mode, the spacecraft passed its closest approach tothe comet (500 km). Thirty minutes after closest approach, thespacecraft again reacquired the nucleus and obtained additional imagesas it departed. The images used for producing the shape model arecontained in the PDS archive of Deep Impact Data for Tempel 1.The data set IDs are: DIF-C-HRIV-2-9P-ENCOUNTER-V1.0 DII-C-ITS-2-9P-ENCOUNTER-V1.0 DIF-C-MRI-2-9P-ENCOUNTER-V1.0  PLATE MODEL A detailed plate model was derived from 70 of the images, usingcontrol points to constrain the shape of the nucleus. 189 differentfeatures on the surface were selected as the control points, with 1520measurements used in the model determination. Approximately 30% ofthe surface is well-defined from these control points, with the restof the surface estimated using other constraints. These additionalconstraints include the positions of the limb and terminator (in boththe approach and lookback images) and the photometric lightcurve ofthe nucleus that was measured in the weeks leading up to theencounter. Adjustments to the shape were also made to shift themoment of inertia in such a way that the spin axis of the nucleuswould reproduce the rotation that was observed during the approachto the comet. The orientation of the spin axis is such that the positive pole pointsto a right ascension of 294 deg and a declination of +73 deg (J2000),with an uncertainty of approximately 5 deg. The prime meridian isdefined by the center of the 350 meter crater located to the west ofthe impact site (in geographic coordinate). Thus, because longitudeincreases in the direction defined by the right hand rule around thepositive pole, the longitude of the impact site is at about 15 degrees.The latitude is -26 degrees. The model, TEMPEL1_PLAN.TAB, is presented in body-centeredplanetocentric coordinates, with vertices at intervals of 2 degrees inboth latitude and longitude. It consists of 16471 vertices, forming32400 plates. The radial distance is given in kilometers and rangesfrom a minimum of 2.3260 km to a maximum 3.9564 km. The shape is suchthat it is not well represented by a triaxial ellipsoid. A second version of the model, TEMPEL1_CART.TAB, was derived from theplanetocentric version. In this version, the vertices are in the samelocations, but are presented in cartesian coordinates. The X axis isdefined in the direction of the intersection of the equator and theprime meridian, the Z axis lies along the positive pole and the Y axiscompletes the right-hand coordinate system. For detailed analysis of the shape, routines such as the SURFACE andPOLYSHADE routines in IDL can be used. To simply view the shapemodel, go to the browse directory, where the shape model has beenconverted to VRML format. There are two versions, one with theillumination that mimics that during the encounter, and one that usesa headlight to reveal the structure in a different manner. Thesemodels can be viewed using any standard VRML viewer. Author------The descriptions in this file were written by Tony Farnham.

Confidence Level Overview : The uncertainties in the pole orientation are approximately 5 degrees.In the regions that are well-defined by control points, the radialuncertainty of the plate model is approximately 20 m. In regions notdefined by control points, the uncertainties are likely to be larger.  Review :The plate model is sceduled for review on Nov 2006.