A portrait of 4979 Otawara, target of the Rosetta Space Mission

A physical portrait based on spectral and photometric data of 4979 Otawara, the first asteroid target of the Rosetta mission, is presented. The aim of this work is to investigate the composition of 4979 Otawara and to evaluate its rotation pole orientation. The spectroscopic observations obtained at the Palomar 200 arcsec and IRTF telescopes cover the wavelength range 0.4 to 2.5 mu m, and provide a definitive classification of Otawara as an S-type asteroid. An analysis of band depths and slopes places Otawara in the S(IV) subgroup, suggesting a similarity to ordinary chondrite meteorites. Moreover we present new photometric data, obtained at the Asiago Observatory and at the TNG telescope, that allow confirmation of the fast rotational period of 2.707+/- 0.005 hours, and a first indication of the spin vector of Otawara. Based on observations obtained at the IRTF Observatory, Hawaii, USA, at the Palomar Mountain Observatory, California, USA, at the TNG telescope, La Palma, Spain and at the Asiago Astrophysical Observatory, Asiago, Italy.