Astronomy and Astrophysics – Astrophysics
Scientific paper
Sep 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008a%26a...487.1187l&link_type=abstract
Astronomy and Astrophysics, Volume 487, Issue 3, 2008, pp.1187-1193
Astronomy and Astrophysics
Astrophysics
12
Minor Planets, Asteroids, Techniques: Image Processing
Scientific paper
Context: Asteroid 2867 Steins is the first target of the Rosetta space mission with a flyby scheduled in September 2008. Aims: An early characterization is needed to optimize the flyby parameters and the science operations, and to maximize the scientific return. Methods: We used the infrared spectrograph (IRS) of the Spitzer Space Telescope (SST) to obtain 14 spectra ranging from 5.2 to 38.0 μm, and to sample the rotational period of the asteroid. The observations were performed on 22 November 2005, when the asteroid was 2.13 AU from the Sun, 1.60 AU from the SST, and at a phase angle of 27.2°. They were interpreted using a standard thermal model incorporating the thermal inertia. Results: The solution for a spherical shape leads to an effective radius rn = 2.46 ± 0.20 km and a thermal inertia I = 150 ± 60 J K-1 m-2 s-1/2, for a beaming factor between 0.8 and 1.0. The geometric albedo is then constrained by visible photometry to pR = 0.31 ± 0.05 and pV = 0.27 ± 0.04 when using a linear phase function. The H-G phase law, which includes an opposition effect, leads to larger values of the albedo, p_R(H-G) = 0.40 ± 0.07 and p_V(H-G) = 0.34 ± 0.06. The solution for our 3-dimensional shape model has overall dimensions of 5.73 ± 0.52 × 4.95 ± 0.45 × 4.58 ± 0.41 km.
Barucci Maria-Antonella
Carvano Jorge
Dotto Elisabetta
Fornasier Sonia
Fulchignoni Marcello
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