2005/09/15 by T. G. Müller, Thomas Müller, T. G. Mueller +7 · 81 citations
Earth and Planetary Sciences · Physics and Astronomy · #Albedo (alchemy) #Asteroid #Astro and Planetary Science #Astrobiology #Astronomy #Astrophysics #Geology #Geometric albedo #High-pressure geophysics and materials #Infrared #Meteorology #Photometry (optics) #Physics #Planetary Science and Exploration #Radiometric dating #Regolith #Remote sensing #Spacecraft #Thermal #astro-ph
paper · pdf · doi:10.1051/0004-6361:20053862
published in Astronomy and Astrophysics 443(1), 347-355 (EDP Sciences) · 9 pages, 7 figures, accepted for publication by A&A 29/Aug/2005
arxiv created 2005/09/15 · openalex publication_date 2005/10/21 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We obtained N- and Q-band observations of the Apollo-type asteroid 25143 Itokawa during its close Earth approach in July 2004 with TIMMI2 at the ESO 3.6 m telescope. Our photometric measurement, in combination with already published data, allowed us to derive a radiometric effective diameter of km and an albedo of 0.19 through a thermophysical model. This effective diameter corresponds to a slightly asymmetrical and flattened ellipsoid of the approximate size of 520(±50) 270(±30) 230(±20) m, based on the Kaasalainen et al. (2005, Proceedings of the 1st Hayabusa Symposium, ASP Conf. Ser., submitted) shape model. Our studies show that the thermal observations lead to size estimates which are about 15% smaller than the radar results (Ostro et al. 2005, Met. Plan. Sci., submitted), slightly outside the stated radar uncertainties of ±10%. We determined a rather high thermal inertia of 750 J m-2 s-0.5 K-1. This is an indication for a bare rock dominated surface, a thick dust regolith can be excluded as well as a metallic surface. From our data we constructed a 10.0 μm thermal lightcurve which is nicely matched in amplitude and phase by the shape and spin vector solution in combination with our TPM description. The assumed S-type bulk density in combination with radiometric size lead to a total mass estimate of kg.