Surface Physical Properties of (21) Lutetia: Results from OSIRIS Observations During the Rosetta Fly-by

On July 10, 2010, the ESA Rosetta mission successfully flew by the asteroid 21 Lutetia, the biggest asteroid ever encountered by a space mission. The OSIRIS imaging system onboard Rosetta, equipped with a Narrow Angle Camera (NAC) and a Wide Angle Camera (WAC), observed the asteroid in 20 filters extending from 240 to 980 nm with a maximum spatial resolution of 60 m/px. Several color sequences were obtained at different rotational phases for the asteroid. Images with the Orange (647 nm) and OI (630 nm) filters of the NAC and WAC cameras were continously repeated to investigate the phase function in a wide phase angle range, from 0 to 156 degrees. In this work we will present unresolved spectrophotometry results, the albedo map and the phase function of 21 lutetia derived by the OSIRIS instrument. Potential albedo variations will be presented as well. We will finally discuss the implications for the mineralogy and the surface evolution of the asteroid.