|R5||D||J2000.0 FK5 (radians)|
|D5||D||J2000.0 FK5 (radians)|
|EPOCH||D||Julian epoch (TDB)|
These orientation and spin components are interpreted as axial vectors. An axial vector points at the pole of the rotation and its length is the amount of rotation in radians.
SLALIB --- Positional Astronomy Library