Techniques d'observation spectroscopique d'astéroïdes

CHAPTER 7. SPECTRAL PROPERTIES OF MAIN BELT ASTEROIDS 127
tel-00785991, version 1 - 7 Feb 2013
Relative Reflectance
(a)
Relative Reflectance
(c)
1.15
1.1
1.05
1
0.95
0.9
0.85
0.8
0.75
0.7
0.65
0.28
0.26
0.24
0.22
0.2
0.18
(3623) Chaplin
0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
Wavelength [um]
0.16
Chaplin
Igneous Plutonic rock
0.14
0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
Wavelength [um]
Relative Reflectance
(b)
Relative Reflectance
(d)
1.2
1.1
1
0.9
0.8
0.7
Chaplin
S
Sv
Sq
0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
Wavelength [um]
0.36
0.34
0.32
0.3
0.28
0.26
0.24
0.22
0.2
Chaplin
0.18
Polymict Breccia rock
0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4
Wavelength [um]
Figure 7.6: a) The NIR averaged spectrum of (3623) Chaplin; b) A polynomial fit for (3623) Chaplin compared
with the theoretical spectra of S, Sv and Sq taxonomic types;; c) the comparison between the spectrum of (3623)
Chaplin and the spectrum of a sample from igneous plutonic rock; d) the comparison between the spectrum of
spectrum of (3623) Chaplin and the spectrum of a sample from low-calcium impact melt breccia rock.
individual spectra of 120 seconds each, for the total integration time of 72 min, while the the
second spectrum (obtained in March 13, 2007) was obtained for the total integration time of 80
min. The S/N was estimated in the range of 15-20.
The NIR spectrum of (3623) Chaplin is typical to S complex asteroids, which is the taxonomic
class of the Koronis family on which Koronis belongs. The classification made using
M4AST gives relatively different solutions compared with the classification made via SMASS
MIT online tool. M4AST gives the solutions: Sv, L and S, while the SMASS MIT online tool
gives S, Sq, Q and L. By visual inspection between these solutions, I consider as possible types
for this spectrum the solutions S, Sv and Sq Fig. 7.6b.
The comparison with laboratory spectra is presented in Table 7.4. The majority of matchings
are among Igneous Plutonic rocks and Polymict Breccia rocks. The fist matching corresponds
to a spectrum of Igneous Plutonic rock, subtype - Gabro Shocked, with crumbed (particles
size between 45 and 75 µm). The second match is a low-Calcium Impact Melt Breccia, a