Abstract
We performed N (10 micron) and Q-band (20 micron) observations of 25143 Itokawa at the ESO La Silla 3.6m telescope with TIMMI2. At last apparition in 2001, Sekiguchi et al. (2003) derived its size and geometric albedo from STM analysis. Our new data in July 2004, in combination with already published data, allowed us to de-termine a radiometric effective diameter of 0.32+/-0.03km and an albedo of 0.19 +0.11/-0.03 through a Thermophysical Model. This effective diameter corresponds to 520 (+/-50) x 270 (+/-30) x 230 (+/-20) m based on the Kaasalainen et al.(2005) shape model with a lightcurve analysis using optical observations data. These re-sults are incompatible with them derived from radar observations in 15 % differ-ences. The obtained thermal inertia indicates a bare rock surface. The total mass of Itokawa was derived to be 4.5x10^10 kg from our results assuming the bulk density for S-type asteroids.
