Techniques d'observation spectroscopique d'astéroïdes
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Techniques d'observation spectroscopique d'astéroïdes

Techniques d'observation spectroscopique d'astéroïdes Techniques d'observation spectroscopique d'astéroïdes

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tel-00785991, version 1 - 7 Feb 2013

7 Spectral properties of Main Belt Asteroids tel-00785991, version 1 - 7 Feb 2013 This chapter describes the spectral properties of six Main-Belt asteroids. The choice to study these objects was made based on the fact that they showed some peculiar physical properties. Thus, (9147) Kourakuen is a vestoid which dynamically could not belong to Vesta family, (854) Frostia is a binary asteroid, (1333) Cevenola and (3623) Chaplin are two asteroids with large amplitude lightcurves, and two asteroids for which it was reported to have pairs (10484) Hecht and (31569) 1999 FL18. The observations presented here are part of the two long term programs which aim to study physical properties of vestoids and of asteroids pairs. The NIR spectra were acquired using the NASA telescope IRTF equipped with the spectro-imager SpeX. The spectra were analyzed applying the techniques described in chapter 4 and chapter 5. I found that (9147) Kourakuen, (854) Frostia, (10484) Hecht and (31569) 1999 FL18 show the characteristics of V-type objects, while (1333) Cevenola, (3623) Chaplin belong to S-complex. The taxonomic classification, the comparison with the meteorite spectra from the Relab database and the mineralogical analysis converged to the same solutions for each of these objects, allowing to find important details for the chemical compositions. Although more than 300,000 asteroids have well established orbital behavior, less than 3% of these have some of their compositional properties determined. To point out the scientific importance of these studies, it can be recalled that the majority of the asteroids have orbits in the region between 2.2 and 3.3 AU. This is the region that defines the transition between terrestrial and giant planets. The majority of knowledge regarding compositional characterization is mainly due to three large surveys: the Eight-Color Asteroid Survey - ECAS [Zellner et al., 1985], S 3 OS 2 [Lazzaro et al., 2004], and the most fruitfully Small Main-Belt Spectroscopic Surveys (SMASSI, SMASSII, SMASS-IR) - Bus & Binzel [2002b]. The analysis of the spectra of six Main Belt asteroids which have some remarkable physical properties is made in the context of previously published physical and dynamical properties of these asteroids. Table 7.1 summarizes some parameters of the considered sample. 7.1 Log of observations The spectral observations were carried out in two sessions: March 2007 and November 2011 using the 3.0 m NASA IRTF telescope located at Mauna Kea - Hawai. The SpeX instrument

tel-00785991, version 1 - 7 Feb 2013

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