GCAT Release 1.2.1 (2021 Aug 15) | Data Update 2021 Sep 19
Spin File Column Descriptions
Each line in the Spin table represents a body defined in the Worlds file,
and gives additional information on the rotational properties of the body.
The Spin and Worlds files are linked by the ID and IDName columns (and
also by the Name column, but that is not guaranteed to be unique).
This one or two character string defines what kind of IDName designation the body has.
Combined with the ID field, the IDName provides a unique identifier for the body.
See the `worlds file' column descriptions for details.
Body mean density in units of 1000 kg/cubic metre (i.e. in grams per cc).
Inertial factor. This dimensionless factor
relates the total angular momentum of
the body to the product of its mass times radius squared,
I = fI M r2
Where no information is available, a default value of 0.33 is used.
- PoleRA, PoleDec
Celestial ICRS position in degrees of the direction of the body's north pole at J2000.0.
Longitude of planetary meridian at J2000.0, degrees.
Rate of change of longitude at J2000.0, degrees per day.
- J2, J4, J6
J2, J4 and J6 spherical harmonics multiplied by one million.
- PoleRARate, PoleDecRate
(degrees/d). Rate of change of ICRS polar RA and Dec at epoch J2000.
A code indicating to software which subroutine to use for detailed polar motion function.
This and the succeeding functions are based on the Report of the IAU Working Group on
Cartographic Coordinates and Rotational Elements 2015 (and later revisions).
A code indicating to software which subroutine to use for detailed spin rate function.
A code indicating to software which subroutine to use for detailed perturbation
functions for the body's moons.
Filename containing higher order spherical harmonics for the body. Currently only the
Earth has such a file. Its contents are:
|Coefficient||Value * 1 million|