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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.

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  f5.1   Slope parameter

  103 -      a      Name

MPC