Spin axis direction of comet 19P/Borrelly based on observations from 2000 and 2001

We calculate the direction of the rotational angular momentum vector, M, of comet 19P/Borrelly based on rotational lightcurve data from 2000, groundbased imaging of the coma during the Deep Space 1 encounter, and the basic near-nucleus coma morphology as revealed by the Deep Space 1 spacecraft. For the most likely direction, we derive a family of solutions ( with center at RA = 221degrees, Dec = -7degrees) if the direction of M is towards the sunward hemisphere during the Deep Space 1 encounter, whereas if the rotation is of opposite sense, the diametrically opposite family of solutions (with center at RA = 41degrees, Dec = 7degrees) would result. We argue that the coma morphology in September 2001 is consistent with the nucleus being a principal axis rotator or one observationally indistinguishable from it. Therefore, for all practical purposes, the direction of the rotational angular momentum vector coincides with the spin axis. We also discuss why the determination of the spin axis direction based on observations from the last apparition is in disagreement with the current result.