EXPLANATIONS FOR ASTEROID FAMILY ASSIGNMENTS                                    
                                                                                
   SUPPLIED BY                                                                  
   J. G. WILLIAMS                                                               
   JPL, 238-332                                                                 
   4800 OAK GROVE DR.                                                           
   PASADENA, CA 91109                                                           
                                                                                
   PHONE: COMMERCIAL 818 354-6466, FTS 792-6466                                 
                                                                                
   DECEMBER 3, 1987                                                             
                                                                                
                                                                                
                                                                                
FAMILY IDENTIFICATIONS ARE GIVEN FOR THE FIRST 1796 NUMBERED ASTEROIDS.         
THESE RESULTS HAVE BEEN EXTRACTED FROM THE FILE OF PROPER ELEMENTS AND          
ARE MOSTLY THE SAME AS GIVEN IN REFERENCE 1 (1979 ASTEROID BOOK).               
THE REVISIONS IN FORMERLY POOR ORBITS HAVE LED TO CHANGES IN FAMILY             
DESIGNATIONS FOR 561, 637, 1037, 1265, 1381, AND 1686.  THE FAMILY              
DESIGNATION FOR 864 IS A RESULT OF THE NEW ORBIT.  PLEASE REFERENCE             
THE ASTEROIDS II BOOK FOR THESE REVISIONS.  FAMILY IDENTIFICATIONS FOR          
PALOMAR-LEIDEN MINOR PLANETS ARE GIVEN IN REFERENCE 2 BELOW.                    
                                                                                
                                                                                
                                                                                
FAMILY FILE                                                                     
                                                                                
EACH OF THE 1796 LINES OF THE FILE CONSISTS OF A FOUR-DIGIT ASTEROID            
NUMBER, A BLANK, AND A THREE CHARACTER FAMILY IDENTIFICATION.  A                
BLANK IDENTIFICATION MEANS NO FAMILY ASSIGNMENT.                                
                                                                                
                                                                                
                                                                                
FAMILIES                                                                        
                                                                                
NUMBERS LESS THAN 100 CORRESPOND TO FAMILIES PREVIOUSLY FOUND                   
   (HIRAYAMA, BROUWER, ARNOLD, OR LINDBLAD AND SOUTHWORTH), BUT                 
   OFTEN ALTERED HERE.  NUMBERS GREATER THAN 100 ARE SIGNIFICANTLY              
   DIFFERENT.  IT SHOULD BE APPRECIATED THAT THE QUALITY AND                    
   UNIQUENESS OF FAMILY IDENTIFICATIONS VARIES WIDELY SINCE MANY                
   FAMILIES ARE POORLY POPULATED, CROWDED, OR OVERLAPPING, WHILE                
   OTHERS ARE ISOLATED OR WELL POPULATED.  THERE ARE 104 FAMILIES:              
   1-4, 21, 24, 36-38, 40, 43, 67, 75, AND 101-191.  FAMILY 1A IS               
   THE CORE OF THE THEMIS FAMILY (1).                                           
                                                                                
                                                                                
                                                                                
REFERENCES                                                                      
                                                                                
REF 1  WILLIAMS, J. G., PROPER ORBITAL ELEMENTS AND FAMILY MEMBERSHIPS          
       OF THE ASTEROIDS, IN ASTEROIDS, ED. T. GEHRELS, UNIV. OF ARIZONA         
       PRESS, 1040-1063, 1979.                                                  
                                                                                
REF 2  WILLIAMS, J. G. AND J. E. HIERATH, PALOMAR-LEIDEN MINOR PLANETS:         
       PROPER ELEMENTS, FREQUENCY DISTRIBUTIONS, BELT BOUNDARIES, AND           
       FAMILY MEMBERSHIPS, ICARUS 72, 276-303, 1987.