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  • Export Format for Comet Orbits

    This document describes the format used for comet orbits in the Extended Computer Service. It also describes the format used for orbits in Ephemerides and Orbital Elements.

    Orbital elements for comets are heliocentric.


    ECS Format

    The column headed `F77' indicates the Fortran 77 format specifier that should be used to read the specified value.
       Columns   F77    Use
    
        1 -   4  i4     Periodic comet number
        5        a1     Orbit type (generally `C', `P' or `D')
        6 -  12  a7     Provisional designation (in packed form)
    
       21 -  24  i4     Year of perihelion passage
       26 -  29  a5     Month of perihelion passage
       30 -  37  f7.4   Day of perihelion passage (TT)
    
       39 -  47  f9.6   Perihelion distance (AU)
       50 -  57  f8.6   Orbital eccentricity
       59 -  63  f5.2   Orbital period (years), if < 100
       60 -  62  i3     Orbital period (years), if >= 100
    
       66 -  73  f8.4   Argument of perihelion, J2000.0 (degrees)
       76 -  83  f8.4   Longitude of the ascending node, J2000.0
                          (degrees)
       86 -  93  f8.4   Inclination to ecliptic, J2000.0 (degrees)
    
       96 -  97  i2     Last two digits of the epoch year
       99 - 103  a5     Month of epoch
      104 - 105  i2     Day of epoch (assumed to be .0 TT)
    OR
       96 - 105         Blank if no epoch
    
    There is no ambiguity in the century part of the epoch, as the
    epoch will be within +/- 20 days of the time of perihelion
    passage.
    
      107 - 111  i5     Number of observations used in solution
      112        a1     '*' indicates non-gravitational parameters
                           considered
    
      114 - 118  a5     Date of first observation (Packed
                           format)
      120 - 124  a5     Date of last observation (Packed
                           format)
    
      126        a1     Source of perturbing coordinates.
                           On the grounds of consistency, standard
                           masses for the perturbing bodies must be used.
      128 - 130  a3     Brief descriptor of perturbers used
                           (blank if unperturbed)
      132 - 135  h4     Fuller description of perturbers used
                           (= `0000' if unperturbed)
      137        i1     Number of perturbing planets (generally `0' for
                           unperturbed solutions or `9' for perturbed
                           solutions)
    
      143 - 172  a30    Name of comet
    
      173 - 181  a9     Reference
    


    Ephemerides and Orbital Elements Format

    The column headed `F77' indicates the Fortran 77 format specifier that should be used to read the specified value.
       Columns   F77    Use
    
        1 -   4  i4     Periodic comet number
        5        a1     Orbit type (generally `C', `P' or `D')
        6 -  12  a7     Provisional designation (in packed form)
    
       15 -  18  i4     Year of perihelion passage
       20 -  21  i2     Month of perihelion passage
       23 -  29  f7.4   Day of perihelion passage (TT)
    
       31 -  39  f9.6   Perihelion distance (AU)
       42 -  49  f8.6   Orbital eccentricity
    
       52 -  59  f8.4   Argument of perihelion, J2000.0 (degrees)
       62 -  69  f8.4   Longitude of the ascending node, J2000.0
                          (degrees)
       72 -  79  f8.4   Inclination in degrees, J2000.0 (degrees)
    
       82 -  85  i4     Year of epoch for perturbed solutions
       86 -  87  i2     Month of epoch for perturbed solutions
       88 -  89  i2     Day of epoch for perturbed solutions
    
       92 -  95  f4.1   Absolute magnitude
       97 - 100  f4.0   Slope parameter
    
      103 - 158  a56    Designation and Name
    
      160 - 168  a9     Reference