The astrometric parameters which serve
as input to the stellar motion model including position at a
specified epoch, proper motion and parallax.
| Name |
Dimension |
Type |
Description |
| Epoch |
DateFormat |
Real Number |
The reference epoch for the object. |
| Julian Epoch |
Unitless |
Real Number |
The epoch of the astrometric data given in Julian
epoch format. The Julian epoch is related to the Julian date by the
expression JD = 2451545.0 + (yyyy.yy - 2000.0) x 365.25, where
2451545.0 (TT) represents the standard J2000 epoch. |
| Reference Frame |
Unitless |
Text |
The reference frame of the astrometric data: J2000
or ICRF. |
| Right Ascension |
LongitudeUnit |
Real Number |
The signed angle measured from the X axis to the
projection of the position vector into the XY plane. The angle
increases in the direction found by the right hand rule about the Z
axis. |
| Declination |
AngleUnit |
Real Number |
The signed angle measured from the XY plane to the
position vector, where positive angles are used for locations above
the XY plane, and negative for those below. |
| Proper Motion RA |
AngleRateUnit |
Real Number |
The component of proper motion that is defined by
the angular rate of right ascension multiplied by the cosine of
declination. |
| Proper Motion
Dec |
AngleRateUnit |
Real Number |
The component of proper motion that is defined by
the angular rate of declination. |
| Radial Velocity |
Rate |
Real Number |
The radial velocity of the star. |
| Parallax |
AngleUnit |
Real Number |
Annual parallax. |
| x |
Unitless |
Real Number |
First component of the selected vector expressed in
the reference set of axes. Defines projection of the vector onto
the x-axis of the reference set. |
| y |
Unitless |
Real Number |
Second component of the selected vector expressed
in the reference set of axes. Defines projection of the vector onto
the y-axis of the reference set. |
| z |
Unitless |
Real Number |
Third component of the selected vector expressed in
the reference set of axes. Defines projection of the vector onto
the z-axis of the reference set. |
| vx |
Unitless Per Time |
Real Number |
X component of unit vector from the solar system
barycenter to the star at the associated epoch. |
| vy |
Unitless Per Time |
Real Number |
Rate of change of Y component of unit vector from
the solar system barycenter to the star at the associated
epoch. |
| vz |
Unitless Per Time |
Real Number |
Rate of change of Z component of unit vector from
the solar system barycenter to the star at the associated
epoch. |