Puzzling rotation of asteroid 288 Glauke

Most asteroids rotate about their axis of maximum moment of inertia. However, for several small asteroids with very slow rotation rates, the damping time scale is expected to be longer than the age of the Solar System, implying that these objects may exhibit non-principal axis rotation. The asteroid 288 Glauke is suspected to undergo tumbling rotation because of very long period of light variations. We observed this object during 39 nights from January to May 2000 at the Borowiec Observatory (Poland). Our lightcurve with a peak-to-peak amplitude of 0.7 mag has a complicated nature which can result from a nonprincipal axis rotation or a very complex shape of this body.