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Export Format for Minor-Planet Orbits

This document describes the format used for both perturbed and perturbed orbits of minor planets, as used in the Extended Computer Service and in the Minor Planet Ephemeris Service.


The column headed `F77' indicates the Fortran 77 format specifier that should be used to read the specified value.

   Columns   F77    Use

    1 -   7  a7     Number or provisional designation
                      (in packed form)
    9 -  13  f5.2   Absolute magnitude, H
   15 -  19  f5.2   Slope parameter, G

   21 -  25  a5     Epoch (in packed form, .0 TT)
   27 -  35  f9.5   Mean anomaly at the epoch, in degrees

   38 -  46  f9.5   Argument of perihelion, J2000.0 (degrees)
   49 -  57  f9.5   Longitude of the ascending node, J2000.0
                      (degrees)
   60 -  68  f9.5   Inclination to the ecliptic, J2000.0 (degrees)

   71 -  79  f9.7   Orbital eccentricity
   81 -  91  f11.8  Mean daily motion (degrees per day)
   93 - 103  f11.7  Semimajor axis (AU)

  106        i1     Uncertainty parameter, U
                    If this column contains `E' it indicates
                    that the orbital eccentricity was assumed.
                    For one-opposition orbits this column can
                    also contain `D' if a double (or multiple)
                    designation is involved or `F' if an e-assumed
                    double (or multiple) designation is involved.

  108 - 116  a10    Reference
  118 - 122  i5     Number of observations
  124 - 126  i3     Number of oppositions

     For multiple-opposition orbits:
     128 - 131  i4     Year of first observation
     132        a1     '-'
     133 - 136  i4     Year of last observation

     For single-opposition orbits:
     128 - 131  i4     Arc length (days)
     133 - 136  a4     'days'

  138 - 141  f4.2   r.m.s residual (")
  143 - 145  a3     Coarse indicator of perturbers
                    (blank if unperturbed one-opposition object)
  147 - 149  a3     Precise indicator of perturbers
                    (blank if unperturbed one-opposition object)
  151 - 160  a10    Computer name

There may sometimes be additional information beyond column 160
as follows:

  162 - 165  z4.4   4-hexdigit flags
                    The bottom 6 bits are used to encode a
                    value representing the orbit type (other
                    values are undefined):

                      Value
                        2  Aten
                        3  Apollo
                        4  Amor
                        5  Object with q < 1.381 AU
                        6  Object with q < 1.523 AU
                        7  Object with q < 1.665 AU
                        8  Hilda
                        9  Jupiter Trojan
                       10  Centaur
                       14  Plutino
                       15  Other resonant TNO
                       16  Cubewano
                       17  Scattered disk

                    Additional information is conveyed by
                    adding in the following bit values:

                       64  Unused
                      128  Unused
                      256  Unused
                      512  Unused
                     1024  Unused
                     2048  Unused
                     4096  Unused
                     8192  1-opposition object seen at
                           earlier opposition
                    16384  Critical list numbered object
                    32768  Object is PHA

  167 - 194  a      Readable designation

  195 - 202  i8     Date of last observation included in
                      orbit solution (YYYYMMDD format)


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