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Statistical Asteroid Model, Version 1.0 (SAM-I)

Overview

What is SAM?

SAM is a database of orbital elements, absolute magnitudes, albedos, and diameters, designed to simulate the population of main belt asteroids with diameters larger than 1 km.

By "simulate", we mean generate ephemerides of main belt asteroids in a given region of sky, for a given date, to an arbitrary brightness limit at wavelengths from ~0.5 to ~60 microns.

SAM's "main asteroid belt" is defined to be those asteroids with orbits between the 4:1 and 2:1 mean-motion resonances with Jupiter, i.e., those with orbital semi-major axes between 2.064 and 3.278 AU, and with modest inclinations (< 25°) and eccentricities (< 0.3). Note that this definition excludes some well-known asteroids, e.g., Pallas (i > 34°). If you wish to include such objects, simply enter the data for them into the Known Main Belt Asteroid Module (described in Table 1 below) for an epoch of osculation of 14 Oct 1998 (JD 2451100.5).

The SAM database consists of 3,810 asteroids with mean opposition magnitudes brighter than the completeness limit (the Known Main Belt Asteroid Module) plus 1,738,310 statistical family members and 142,587 statistical background asteroids (the Statistical Asteroid Module) generated by the model. Thus, the total number of asteroids in SAM is 1,880,897.

The SAM database consists of two files: A Known Asteroid Module file (295,481 bytes) and a Statistical Asteroid Module file (171,163,107 bytes). Both files are available here and described in Tables 1 and 2, below. Our ultimate goal is to create reliable SFD models for the entire main asteroid belt and Near-Earth Asteroids (NEAs) down to ~100 meters to provide accurate descriptions of the present NEA and main-belt asteroid populations.

Table 1. Format of the Known Main Belt Asteroid Module

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  ID      a        e        i         H     Va0  Diam   Albedo Fam Data Class BMV

  (1)     (2)      (3)      (4)       (5)   (6)  (7)    (8)    (9) (10) (11)  (12)

-----------------------------------------------------------------------------------

        1 2.765674 0.078054 10.58392  3.34  6.79 848.40 0.1132   3   1   G    0.713

        3 2.668964 0.258076 12.96754  5.33  8.58 233.92 0.2383   3   1   S    0.824

        4 2.361200 0.090150  7.13422  3.20  5.73 500.74 0.3698 VES   1   V    0.782

        5 2.573253 0.192006  5.36820  6.85  9.88 119.07 0.2268   3   1   S    0.826

        6 2.424757 0.202120 14.77090  5.71  8.39 185.18 0.2679   2   1   S    0.822

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Table 2. Format of the Statistical Main Belt Asteroid Module

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  Tp           q          e         ArgPer      AscNode   i        H     Diam  Albedo   Fam

  (1)         (2)        (3)        (4)         (5)       (6)      (7)   (8)   (9)      (10)

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2451425.64627 0.86789162 0.61636156  65.906639  23.627751 12.66608 16.97  2.03 0.0699   2

2451030.80383 2.32645240 0.01160324 295.530832   0.687053 38.51037 13.99  7.17 0.0874   2

2450971.16822 1.72885506 0.27752471 252.540987 355.328321 32.20858 15.69  3.45 0.0785   2

2450498.66417 1.31538199 0.44383794 295.157640 355.334158 20.50919 13.97 10.81 0.0391   2

2451661.82002 0.98545036 0.56064367 249.238801 122.786894  8.86987 13.94  8.25 0.0690   2

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How SAM was Created

SAM is based upon an analysis starting in April 1998 when the known population was 38,629 (of which 8,603 were numbered); thus, the model is based upon this set of 8,603 numbered asteroids.

The model is based on a population of ~1.9x106 asteroids obtained from the complete known asteroid sample, plus extrapolation of the size-frequency distributions of 15 asteroid dynamical families and three background populations, to a diameter limit of 1 km.

For complete details, see:
Tedesco, E.F., Cellino, A., and Zappalą, V. (2005). The Statistical Asteroid Model: I. The Main-Belt Population for Diameters Greater than 1 km. Astron. J. 129, 2869-2886.

How SAM is Meant to be Used

The two files described above are meant to be used as input to an ephemeris code that can generate positions and magnitudes (or fluxes) for SAM asteroids in a given region of sky, for a given date, to an arbitrary brightness limit at wavelengths from ~0.5 to ~70 microns.

E. Tedesco
Ed.Tedesco@unh.edu
Durham, NH
15 Feb 2005


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