NEAR Radio Science Subsystem Gravity and Landmark Files                       
=======================================================                       
                                                                              
The following information was included in the data set catalog file           
of the original data submission.  The "Parameters" section has been           
edited to reflect the current state of the files in this collection.          
                                                                              
                                                                              
  Data Set Overview                                                           
  =================                                                           
  This data set includes a 15x15 gravity model for Eros derived               
  from radio and landmark tracking of the NEAR spacecraft, several            
  images/maps, and a file of surface landmarks.  The gravity model and        
  images/maps were produced by Alex Konopliv of the NEAR                      
  Radio Science Team at the NASA Jet Propulsion Laboratory.  The              
  landmark file was compiled by the NEAR Navigation Team and was              
  used in the solution for the gravity field.                                 
                                                                              
                                                                              
  Parameters                                                                  
  ==========                                                                  
  The gravity model is defined by a set of spherical harmonic                 
  coefficients -- GM, Cmn, and Smn.  These can be evaluated to                
  give the gravitational potential of Eros.  The coefficients                 
  and their individual uncertainties are provided in one ASCII                
  table file.  The covariance table is supplied in a separate                 
  ASCII file.  General model parameters (GM, pole position, etc.)             
  are included in the labels of both these files.                             
                                                                              
  Several image files contain digital maps of Bouguer anomaly and             
  radial gravity acceleration where the gravity field has been                
  evaluated to degree and order less than the full 15x15 range in             
  the model.  The truncation reduces noise in the maps resulting              
  from uncertainty in the higher degree and order coefficients.               
  Three maps are provided, truncated to orders 5, 6 and 7.                    
                                                                              
  The landmark file contains rotation information for Eros and                
  X, Y, and Z coordinates for the centers of craters identified               
  on its surface.                                                             
                                                                              
                                                                              
  Processing                                                                  
  ==========                                                                  
  Spherical harmonic models and maps were derived from raw radio              
  tracking data in several steps.                                             
                                                                              
  The gravity field coefficients were obtained by solving systems             
  of equations with about 5000 unknowns.  Radio tracking data                 
  in long arcs were delimited mostly by propulsive maneuvers                  
  and were used in solutions which were obtained iteratively                  
  and by least squares.                                                       
                                                                              
  Maps of vertical gravity acceleration and Bouguer anomaly were              
  generated from the spherical harmonic model(s) evaluated at                 
  regular grid points.                                                        
                                                                              
                                                                              
  Coordinate System                                                           
  =================                                                           
  The gravity model, maps, and landmark file use the IAU 1994                 
  right ascension and declination system [DAVIESETAL1996A].                   
  The Eros prime meridian is fixed at 326.08 degrees.                         
                                                                              
                                                                              
  Overview                                                                    
  ========                                                                    
  Data in this archive have been reduced as part of mission data              
  analysis activities of the NEAR Radio Science Team.  Data of                
  questionable validity have been omitted from the solutions.                 
                                                                              
                                                                              
  Data Coverage and Quality                                                   
  =========================                                                   
  The data included in this archive were collected during the                 
  NEAR orbital phase from 2000-02-14 to 2001-02-12.