Shape Dataset Organization                            
                                                                              
This shape-model dataset includes a wide variety of shape models of comet     
67P/Churyumov-Gerasimenko.  They have been developed by several different     
groups, using data from several different portions of the Rosetta mission,    
using a variety of techniques, and intended for a variety of different        
purposes.  Several of these models have been cited in the literature as       
underlying various investigations.  The different shape models are collected  
together in order to make it easier for users to choose the appropriate       
model, but the wide variety means that there are many possible ways to        
organize the archive.                                                         
                                                                              
This dataset includes several models, with the potential for additional       
models to be added.  This document describes the generic organization for the 
models that are planned to be archived.  All the shape models tesselate the   
surface of the nucleus into triangular, flat plates.  At the highest level,   
the datasets are separated into ascii formats and binary formats.  The binary 
formats are exclusively the Digital Shape Kernels that are used in SPICE.     
The ascii versions are designed for non-SPICE users and for simple            
visualization of the geometry.  They always include an ascii version that     
follows the standard used in PDS-SBN for decades (long prior to the           
availability of DSK) that includes a wrapper that makes them viewable in any  
VRML-aware application, of which there are many available.                    
                                                                              
At the next level, the models are divided into groups corresponding to the    
team that produced the models and the method that team used.  The four groups 
at this level are, as abbreviated in directory names and file names: 1)       
mspcd_lam, Modified StereoPhotoClinometry by Distortion, produced at the      
Laboratoire d'Astrophysique de Marseille, 2) spc_esa, StereoPhotoClinometry   
produced by the flight operations team of ESA (European Space Agency) and     
converted to standard formats by the Rosetta Mission Operations Center        
(RMOC), 3) spc_lam_psi, StereoPhotoClinometry produce by a collaboration      
between the Laboratoire d'Astrophysique de Marseille and the Planetary        
Science Institute, and 4) spg_dlr, Stereo-PhotoGrammetry produced at the      
German Aerospace Center (DLR) group in Berlin.  This grouping also separates  
the models by the instruments used to obtain the input images, the models     
from ESA having been derived entirely from the NAVCAMs (NAVCAM1 and NAVCAM2   
are nominally identical), whereas the other three groups are based entirely   
on the scientific cameras, OSIRIS-NAC and OSIRIS-WAC.  At this writing, there 
are currently no models available in group 4.  See other documents to         
understand the differences among the techniques.                              
                                                                              
At the third level, the models are sorted by the time period of the data      
used, which affects the geographic coverage of the data and the best spatial  
resolution achieved.  For the models from ESA, this is denoted by the last    
MTP (Medium Term Planning) cycle of the data, whereas for the models using    
the scientific cameras, the OSIRIS teams used sequential numbers to           
differentiate the time periods, with details given in the relevant            
subdirectories.                                                               
                                                                              
At the next level, because the full-resolution models are very large, there   
are models with various levels of reduced resolution available, intended for  
purposes that do not require the highest resolution and therefore speed up    
calculations.