Physical characterization of (333358) 2001 WN1: a large, possibly water-rich, low delta-V near-Earth asteroid.
ATel #4623; M. Hicks (JPL/Caltech), D. Dombroski (LACC)
on 6 Dec 2012; 23:41 UT
Credential Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)
Subjects: Optical, Asteroid, Solar System Object, Near-Earth Object
The near-Earth asteroid (333358) 2001 WN1 was discovered on 2001 November 17 by the LINEAR NEO survey (MPEC 2001-W30). We obtained one night of Bessel BVRI on 2012 November 25 at the JPL Table Mountain Observatory (TMO) 0.6-m telescope. The observational circumstances are summarized in Table 1, with heliocentric, geocentric, solar phase angle, lunar elongation, and expected V magnitude as computed by the JPL HORIZONS ephemeris service.
The object's rotationally averaged colors (B-R=1.105+/-0.038 mag; V-R=0.402+/-0.023 mag; R-I=0.336+/-0.012 mag) were found most compatible with a C-type spectral classification (Bus Taxonomy), an association obtained through a comparison of our colors with the 1341 asteroid spectra in the SMASS II database (Bus & Binzel 2002) [Figure 1 and Table 2]. The C-type asteroids are generally accepted as consistent with a low albedo and a surface composition possibly analogous to the water-rich carbonaceous chondrite meteorites. Assuming a solar phase parameter g=0.05 and a double-peaked lightcurve, we found a best-fit period P_syn=3.21+/-0.01 hr [Figure 2]. The object's absolute magnitude H_V=19.64+/-0.02 mag implies a diameter D~0.7 km. assuming an albedo rho=0.05.
To first order, the spacecraft rendezvous potential of a small solar system body can be quantified by the delta-V needed to match the target's orbit. Using the method described by Shoemaker & Helin (1978; N78-29022) a delta-V=6.295 km/s is required to reach the orbit of Mars. With a delta-V=6.288 km/s 2001 WN1 can be considered a low delta-V target [Figure 3]. Using absolute magnitude as a proxy for size, we note that 2001 WN1 is in the upper 94th percentile among known low delta-V NEOs.
Copyright 2012. All rights reserved. The research described in this telegram was carried out at the Jet Propulsion Laboratory, under a contract with the National Aeronautics and Space Administration. The student participation was supported by the National Science Foundation under REU grant AST-1156756 to Los Angeles City College.
Table 1: Observational circumstances.
Solar Lunar Exp.
UT DATE r delta Phase Elong. V Observer
[AU] [AU] [deg] [deg] [mag]
2012 11 25.24 1.146 0.160 6.7 29.5 16.2 Dombroski
Table 2: Best-fit SMASS II spectral analogs.
Taxonomic Class
Misfit Object Name (Bus)
0.900 2161 Grissom C
0.901 2194 Arpola Xc
0.907 965 Angelica Xc
0.918 3567 Alvema Xc
0.946 1114 Lorraine Xc
