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Planetary radar targets 1999 AP10, 2000 TO64, 2000 UJ1, and 2000 XK44: Four S-complex near-Earth asteroids.

ATEL # 2323; M. Hicks (JPL/Caltech), K. Lawrence (JPL/Caltech)
on 2 Dec 2009; 21:25 UT
Password Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)

Subjects: Optical, Asteroids, Planets, Planets (minor), Solar System Objects

We report taxonomic classifications of four near-Earth asteroids (1999 AP10, 2000 TO64, 2000 UJ1, and 2000 XK44) scheduled for radar observation by the JPL radar group at the Arecibo facility in Oct-Nov 2009, using long-slit CCD spectroscopy acquired at the Palomar 5-m telescope on 2009 Nov 09 UT. Table 1 lists the observation circumstances. Normalized reflectance spectra are shown in Figures 1-4 [1][2][3][4] A comparison of our optical spectra with the 1341 asteroid spectra as archived in the SMASS II database (Bus & Binzel 2002) was used to determine taxonomy and we found 1999 AP10 (L-type), 2000 TO64 (Sq-type), 2000 UJ1 (S-type), and 2000 XK44 (S-type) to all be members of the S-type spectral complex. Table 2 list the five best-fit SMASS II analogs for each of our asteroids. All targets excluding 2000 XK44 were observed on 2009 Oct 19 UT (ATEL#2283), with similar results. Due to evolution of the observational geometry, 2000 UJ1 had brightened by 4.3 magnitudes from Oct 19 to Nov 9, therefor taxonomy from the later date is significantly more robust.

Near-IR spectroscopy and thermal flux measurements for each target over the remainder of their apparitions would be extremely useful to help further constrain size, albedo, and surface composition.

Copyright 2009. All rights reserved. The research described in this telegram was carried o ut at the Jet Propulsion Laboratory, under a contract with the National Aeronautics and Space Administration.

   Table 1:  Observational Circumstances.      Object Name   r (AU)  delta (AU)  p (deg)  V (mag)  Exp Time (min)   1999 AP10     1.013     0.118      75.9     14.0        16.0   2000 TO64     1.053     0.115      54.4     14.3        17.0   2000 UJ1      1.077     0.114      38.4     14.7        10.0   2000 XK44     1.066     0.077      10.9     13.3        11.0   


   Table 2:  Best-fit SMASS II spectral analogs.                                TAXONOMIC CLASS   MISFIT  OBJECT NAME        (THOLEN) (BUS)          - for 1999 AP10 -   0.666   42 Isis               S       L   0.785  824 Anastasia          S       L   0.790 3287 Olmstead                   L   0.799 1882 Rauma                      K   0.846  100 Hekate             S       S          - for 2000 TO64 -   0.387      1995 BM2                   Sq   0.492 1293 Sonja                      Sq   0.518 2042 Sitarski                   Sq   0.543 2902 Westerlund                 Sq   0.566 7056 Kierkegaard                Sq          - for 2000 UJ1 -   0.288 2282 Andres Bello               S   0.387 4200 Shizukagozen               S   0.446 5534 1941 UN                    S   0.457 5552 Studnicka                  S   0.465 2478 Tokai                      S          - for 2000 XK44 -   0.433 2282 Andres Bello               S   0.480 4200 Shizukagozen               S   0.515  462 Eriphyla           S       S   0.525 2478 Tokai                      S   0.532  403 Cyane              S       S   



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