ESA versions of the 67P/Churyumov-Gerasimenko nucleus shape model The ESA versions of the dataset (MTP009 and MTP019) represent the shape models created by the Flight Dynamics group of the Rosetta Mission Operations Centre (RMOC) at ESOC in Germany. ESA versions of the model --------------------------- The ESA models of 67P were developed by the flight dynamics team for navigation of the Rosetta spacecraft. They were created using NAVCAM images using photoclinometry techniques. MTP009 was developed using observations obtained between Aug 6 and Nov 2, 2014. This was before the south pole had become illuminated, so there are regions on the surface that are not constrained by observations. These unconstrained areas of the surface appear smooth in the models. MTP0019 was developed using observations from the escort phase, which spanned Aug 6, 2014 through Aug 25, 2015. This version includes the full surface of the nucleus. Reference Frame and Coordinate System --------------------------------------- The shape models adopt the body reference frame and rotation state defined by Scholten et al ('Reference Frames and Mapping Schemes of Comet 67P/C-G' in the PDF document CHEOPS_REF_FRAME_V1.PDF in the DOCUMENTS directory). The body's coordinate system was defined with the +Z axis in the direction of the spin axis and the prime meridian (+X axis) is defined such that the center of the large boulder named Cheops is at a longitude +142.35 degrees, following the IAU definition presented in the document CHEOPS_REF_FRAME_V1.PDF. The +Y axis completes the right-hand coordinate system. Data Formats -------------- The models are presented in several different formats, all of which present the triangular plate information with dimensions of km in cartesian coordinates. For the complex shape of 67P, spherical coordinates (lat/long/radius) result in multiple values in some regions of the nucleus, so the model is not presented in this form. 1) The WRL file gives the standard PDSSBN vertex/triangular plate format (see PDSSBN_PLATE_SHAPE_DEF.ASC in the documents directory). These files are presented with VRML wrappers that allow the model to be displayed with existing VRML viewers that are freely available (e.g., INSTANT PLAYER, OCTAGA, CORTONA, etc.). 2) The ROS version is essentially the same as the WRL format without the VRML wrapper. 3) The OBJ version is the triangular plate model presented in a form that that can be adapted for use with 3-D printers 4) The DSK version presents the model as a SPICE kernel that can be used with the NAIF SPICE utilities. Model Resolutions ------------------- The ESA shape models are provided at two different resolutions, with a high resolution version providing the most detail, and the low resolution version that can reduce the necessary calculations for a given problem if the high resolution is not needed. Details about the ESA MTP009 shape model files CSHP_DV_047_02_HIRES_WRL.WRL - 2000258 vertices forming 4000512 facets CSHP_DV_047_01_LORES_WRL.WRL - 125018 vertices forming 250032 facets Details about the ESA MTP019 shape model files CSHP_DV_130_01_HIRES_WRL.WRL - 833538 vertices forming 1667072 facets CSHP_DV_130_01_LORES_WRL.WRL - 52098 vertices forming 104192 facets TABLE: Shape Model Characteristics (for the high-res MTP019 model) Surface Area: 48.3 km^2 Volume: 18.8 km^3 Mean diameter: 3.3 km (diameter of sphere of equivalent vol.) Axis orientation: RA: 69.4 +/- 0.2 deg Dec: +64.1 +/- 0.2 deg Rotation Period: 12.4041 +/- 0.0001 hr