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In late 2010 a Jupiter Family comet 103P/Hartley 2 was a subject of anintensive world-wide investigation. On UT October 20.7 the comet approached theEarth within only 0.12 AU, and on UT November 4.6 it was visited by NASA'sEPOXI spacecraft. We joined this international effort and organized anobserving campaign. The images of the comet were obtained through narrowbandfilters using the 2-m telescope of the Rozhen National AstronomicalObservatory. They were taken during 4 nights around the moment of the EPOXIencounter. Image processing methods and periodicity analysis techniques wereused to reveal transient coma structures and investigate their repeatabilityand kinematics. We observe shells, arc-, jet- and spiral-like patterns, verysimilar for the CN and C3 comae. The CN features expanded outwards with thesky-plane projected velocities between 0.1 to 0.3 km/s. A corkscrew structure,observed on November 6, evolved with a much higher velocity of 0.66 km/s.Photometry of the inner coma of CN shows variability with a period of18.32+/-0.30 h (valid for the middle moment of our run, UT 2010 Nov. 5.0835),which we attribute to the nucleus rotation. This result is fully consistentwith independent determinations around the same time by other teams. Thepattern of repeatability is, however, not perfect, which is understendablegiven the suggested excitation of the rotation state, and the variabilitydetected in CN correlates well with the cyclic changes in HCN, but only in theactive phases. The revealed coma structures, along with the snapshot of thenucleus orientation obtained by EPOXI, let us estimate the spin axisorientation. We obtained RA=122 deg, Dec=+16 deg (epoch J2000.0), neglecting atthis point the rotational excitation.

Rotation-stimulated structures in the CN and C3 comae of comet 103P/Hartley 2 around the EPOXI encounter