Techniques d'observation spectroscopique d'astéroïdes
Techniques d'observation spectroscopique d'astéroïdes
Techniques d'observation spectroscopique d'astéroïdes
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98 CHAPTER 6. SPECTRAL PROPERTIES OF NEAR-EARTH ASTEROIDS<br />
(8567) 1996 HW1<br />
Taxonomic classification for (8567) 1996 HW1<br />
1.2<br />
1.2<br />
Relative Reflectance<br />
(a)<br />
1.15<br />
1.1<br />
1.05<br />
1<br />
0.95<br />
0.9<br />
0.85<br />
0.8<br />
0.75<br />
0.7<br />
V<br />
NIR<br />
0.5 1 1.5 2 2.5<br />
Wavelength [um]<br />
Relative Reflectance<br />
(b)<br />
1.1<br />
1<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
Spectrum<br />
S<br />
Sq<br />
0.5 1 1.5 2 2.5<br />
Wavelength [um]<br />
tel-00785991, version 1 - 7 Feb 2013<br />
Relative Reflectance<br />
(c)<br />
0.22<br />
0.21<br />
0.2<br />
0.19<br />
0.18<br />
0.17<br />
0.16<br />
0.15<br />
0.14<br />
0.13<br />
Asteroid<br />
0.12<br />
Relab sample<br />
0.5 1 1.5 2 2.5<br />
Wavelength [um]<br />
Relative Reflectance<br />
(d)<br />
0.34<br />
0.32<br />
0.3<br />
0.28<br />
0.26<br />
0.24<br />
Asteroid<br />
Relab sample<br />
0.5 1 1.5 2 2.5<br />
Wavelength [um]<br />
Figure 6.2: a) The visible [Vernazza, 2006] and the NIR spectra of (8567) 1996 HW1; b) a polynomial fit of the<br />
V+NIR spectrum of (8567) 1996 HW1 compared with the theoretical spectra of S and Sq types; c) reflectance spectrum<br />
of (8567) 1996 and the closest match resulting from the meteorite comparison - the LL4 ordinary chondrite<br />
Hamlet; d) de-reddened spectrum of (8567) 1996 HW1 and the closest match resulting from meteorite comparison<br />
-the LL6 ordinary chondrite Cherokee Springs.<br />
(Fig. 6.2a) before analyzing the composite spectrum.<br />
Using the taxonomic classification tool from the MIT-SMASS, this NEA is classified as an<br />
S-type with the spectral slope 0.2245 µm −1 . Using the M4AST approach, it can be found that<br />
an Sq type provides a closer fit spectrum than an S (Fig. 6.2b). Sq type is at the transition<br />
between S and Q classes with two absorption bands around 1 µm and 2 µm that are more<br />
shallow than for Q-type [DeMeo et al., 2009]. Comparing the features for the two considered<br />
spectral types with a polynomial fit of the spectrum, it can be observed that an Sq type matches<br />
more closely the obtained data than an S type. Since there are no measurement of the albedo<br />
for this object, assuming a value of 0.20 as typically found for the albedo of S-type asteroids<br />
[Fulchignoni et al., 2000], the diameter can be estimated to be ≈ 2.5 km.<br />
The spectrum from the Relab sample that provides the closest fit is a particulate ground<br />
sorted (0-125 µm) Hamlet meteorite (sample ID: OC-TXH-002-C), an ordinary chondrite with
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