***** File  EPHEM.TXT                                                         
                                                                              
EPHEMERIS                                                                     
                                                                              
     The geocentric ephemeris for 0h UT each day has been calculated by the   
Astrometry Network from the following set of osculating orbital elements      
(Astrometry Network orbit no. 37).  The orbital solution was fit to 1145      
astrometric observations over the interval from 1972 March 11 to 1987 March 31
with a rms residual = 1.1 arcsec.  Full planetary and nongravitational        
perturbations have been taken into account at each time step in the ephemeris 
computations.  The angular elements are referred to the ecliptic plane and the
equinox of 1950.                                                              
                                                                              
     Epoch of Osculation              1985 Sept. 12.0 ET                      
     Time of Perihelion Passage       1985 Sept.  5.20602 ET                  
     Perihelion Distance              1.0282677 AU                            
     Eccentricity                     0.7075130                               
     Argument of Perihelion           172.48430 deg.                          
     Longitude of Ascending Node      194.70674 deg.                          
     Inclination                       31.87869 deg.                          
                                                                              
     Nongravitational Parameters:                                             
                                                                              
     Radial component, A1          +3.166 E-09 AU/(day)**2                    
     Transverse component, A2      -0.599 E-09 AU/(day)**2                    
                                                                              
     The nongravitational acceleration model is outlined in the following     
reference:                                                                    
     Marsden, B.G., Sekanina, Z., and Yeomans, D.K.  Comets and               
     nongravitational forces. V.  In Astronomical journal, v. 78, 1973,       
     p. 211 - 225.                                                            
                                                                              
     The definition of each output quantity is given below:                   
(Each line of the table is a fixed width of 106 characters plus <CR> <LF>.)   
                                                                              
     Date:    Calendar date and Julian date (times in these ephemerides are   
              universal times).                                               
     RA, DEC: Geocentric right ascension and declination referred to the      
              mean equator and equinox of 1950.0 - light time corrections     
              have been applied.                                              
     DELTA:   Geocentric distance of comet in AU.                             
     DELDOT:  Geocentric velocity of comet in km/sec.                         
     R:       Heliocentric distance of comet in AU.                           
     RDOT:    Heliocentric velocity of comet in km/sec.                       
     THETA:   Sun-Earth-Comet angle in degrees.                               
     BETA:    Sun-Comet-Earth angle in degrees.                               
     MOON:    Comet-Earth-Moon angle in degrees.                              
     PSANG:   Position angle of extended Sun-Comet vector.                    
     PSAMV:   Position angle of minus comet velocity vector.                  
                                                                              
     (Position angles are measured east from north.)                          
                                                                              
                                                                              
Ravenel N. Wimberly                                                           
Astrometry Team Member                                                        
Jet Propulsion Laboratory                                                     
4800 Oak Grove Drive                                                          
Pasadena, CA 91109