'Calculate the GCRS position and velocity of this object at the
requested ``obstime``.
Parameters
obstime : `~astropy.time.Time`
The ``obstime`` to calculate the GCRS position/velocity at.
Returns
obsgeoloc : `~astropy.coordinates.CartesianRepresentation`
The GCRS position of the object
obsgeovel : `~astropy.coordinates.CartesianRepresentation`
The GCRS velocity of the object'

def get_gcrs_posvel(self, obstime):

    from .builtin_frames import GCRS
    itrs = self.get_itrs(obstime)
    geocentric_frame = GCRS(obstime=obstime)
    obsgeoloc = itrs.transform_to(geocentric_frame).cartesian
    vel_x = ((- OMEGA_EARTH) * obsgeoloc.y)
    vel_y = (OMEGA_EARTH * obsgeoloc.x)
    vel_z = (0.0 * vel_x.unit)
    obsgeovel = CartesianRepresentation(vel_x, vel_y, vel_z)
    return (obsgeoloc, obsgeovel)
