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 f5.1 Slope parameter
103 - a Name
