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Broadband photometry of 3988 (1986 LA): A large low-ΔV near-Earth Asteroid

ATel #3457; M. Hicks (JPL/CalTech), T. Truong (CSULA), C. Gerhart (LAVC), M. McCormack (LACC), C. Strojia (VVC), S. Teague (VCC)
on 28 Jun 2011; 19:51 UT
Credential Certification: Michael D. Hicks (Michael.Hicks@jpl.nasa.gov)

Subjects: Optical, Asteroid, Planet (minor), Solar System Object, Near-Earth Object

The Near-Earth Object (NEO) 3988 (1986 LA) was discovered photographically by Glo Helin and colleagues with the 1.2-m Schmidt at Palomar (Helin et al. 1986: IAU Circ. 4228). With a perihelion distance q = 1.055 AU, 1986 LA is an Amor-type NEO. The spacecraft rendezvous potential of any small solar system body can be quantified, to first order, by the dV required to match the target's orbit. Using the method described by Shoemaker & Helin (1978; N7829022) and assuming a massless rendezvous target, a dV of 6.29 km/s is required to reach the orbit of Mars. Objects with dV < 6.29 km/s can therefor be considered low-dV targets: 1791 NEOs meet this criteria. 1986 LA has a dV of 5.84 km/s and is shown as a red symbol in Figure 1. With an absolute magnitude H = 17.7 (Lowell Astorb Database), the object is in the top 0.985 percentile in terms of expected size.

We obtained four nights of Bessel BVRI on 2011 June 14, 15, 16, and 18 at the JPL Table Mountain 0.6-m telescope. The observational circumstances are listed in Table 1. Our analysis was hampered by the high density of background stars, the low lunar elongation, and an intermittent tracking error. The rotationally averaged colors listed in Table 2 (B-R = 1.487+/-0.116 mag; V-R = 0.520+/-0.105 mag; R-I = 0.461+/-0.098 mag) were found most consistent with an Ld-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 2. and Table 3]. Despite the large error bars in our photometry we are confident that 1986 LA belongs to the S-family of asteroids (Tholen Taxonomy). Assuming a phase parameter G=0.15 and our V-R color, we measured an absolute magnitude H_V = 17.97 +/- 0.15 mag, intermediate between the H_V = 17.7 mag (Lowell) and H_V = 18.2 mag (JPL) database listings. Collaborative observations with other researchers would be very welcomed.

Copyright 2011. 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 0852088 to Cal State LA.

 
Table 1:   Observational circumstances. 
 
                            Solar  Galactic    Num. 
   UT DATE      r    delta  Phase  Long. Lat.  Exp.   Observers 
               [AU]   [AU]  [deg]  [deg] [deg] 
2011 06 14.33 1.155  0.196   41.3   51.6  5.4   65   McCormack, Gerhart 
2011 06 15.27 1.151  0.194   42.2   53.0  5.6   46   Truong, Strojia 
2011 06 16.32 1.148  0.193   43.2   54.6  5.7  107   Gerhart, Teague 
2011 06 18.34 1.141  0.190   45.3   57.7  6.1   83   Truong, Gerhart, McCormack 
 
 
 
Table 2:  Relative Colors. 
 
UT Date          B-R            V-R            R-I       mean R 
                [mag]          [mag]          [mag]      [mag] 
2011 06 14  1.653+/-0.180  0.378+/-0.164  0.406+/-0.202  15.71 
2011 06 15  1.375+/-0.132  0.559+/-0.153  0.442+/-0.082  15.89 
2011 06 16  1.578+/-0.080  0.605+/-0.071  0.395+/-0.078  15.83 
2011 06 18  1.298+/-0.184  0.444+/-0.133  0.486+/-0.102  15.86 
mean:       1.487+/-0.116  0.520+/-0.105  0.461+/-0.098  15.84 
 
 
 
Table 3:  Best-fit SMASS II spectral analogs. 
 
                         Taxonomic Class 
Misfit  Object Name      (Tholen)  (Bus) 
 
0.312 2850 Mozhaiskij                Ld 
0.377 4917 Yurilvovia                Ld 
0.597  234 Barbara           S       Ld 
0.739 5840 1978 ON                   Ld 
0.759 7245 1991 RN10                 L