Techniques d'observation spectroscopique d'astéroïdes

94 CHAPTER 6. SPECTRAL PROPERTIES OF NEAR-EARTH ASTEROIDS
Table 6.1: Some characteristics of the observed NEAs: orbit type, semi-major axis, eccentricity, inclination,
absolute magnitude (H), and the delta-V.
Object Orbit Type a e i ∆V [km/s] H
Cuyo Amor 2.15005205 0.50448184 23.943786 8.556 14.7
Jasonwheeler Amor 2.15783969 0.42369152 7.861788 6.974 17.0
1996 HW1 Amor 2.04580925 0.44905867 8.439303 6.495 15.4
1998 QS52 Apollo 2.20249841 0.85791440 17.563883 11.11 14.2
2005 GN59 Apollo 1.65644063 0.46770919 6.627004 6.002 17.4
2004 HE62 Amor 2.55781560 0.56690184 24.685809 9.074 17.3
2001 SG286 Apollo 1.35819973 0.34708703 7.772096 5.604 20.9
2010 TD54 Apollo 1.97198039 0.64352131 4.809727 - 28.7
tel-00785991, version 1 - 7 Feb 2013
Popescu et al., 2011]. Their accessibility enables their scientific study, their practical study,
and their detailed assessment for their future use as space resources.
In this chapter are describe spectroscopic results for eight NEAs in the 0.8-2.5 µm spectral
region. Some of their dynamical characteristics are summarized in Table 6.1. The asteroids
were observed during several runs between 2008 and 2010 as part of a project for studies
of NEA physical properties, and potential targets of spacecraft missions. I modeled and interpreted
the acquired spectra using the techniques described in chapter four with the goal
of achieving basic interpretations regarding the composition and physical processes that took
place at the surface of these asteroids.
6.1 Log of observations
In contrast to the Main-Belt asteroids, the asteroids classified as NEA do not often have a
favorable geometry for ground-based observations. The small diameters of the majority of
NEAs impose tight constraints on the suitable geometries of observations for determining the
reflective properties of their surfaces. These conditions are usually met in the case of a close
approach to the Earth, when the apparent magnitude decreases by several magnitudes. These
suitable geometries occur on average, only five times per century.
The technical limitations like differential tracking, diameter of the principal mirror of the
telescope and the sensitivity of the detectors should be also taken into account.
The spectral data described here were obtained in the 0.8 - 2.5 µm spectral region with the
SpeX/IRTF instrument. The observations were carried out in two sessions: in August 2008
and in May 2009. The remotely observing procedure from CODAM was used. The spectrum
of 2010 TD54 was received from professor R. Binzel (private communication). For all the
observations the low resolution prism mode (R≈100) of the spectrograph was used. A 0.8×15
arcsec slit oriented north-south was used. The spectra of the asteroids and the solar analog stars
were obtained using the nodding procedure.
Log of the observations is given in Table 6.2. In general, the asteroid spectra were obtained
taking images with an integration time (Itime) of 120s, for several cycles, to increase the S/N