Data Set Information
ASTEROID (101955) BENNU SHAPE MODEL V1.0
Shape model of 101955 Bennu from Arecibo/Goldstone radar and
Data Set Overview
Asteroid (101955) Bennu was discovered in September 1999 by the LINEAR
survey and designated 1999 RQ36. It is an Apollo Near-Earth Object (NEO)
with a semi-major axis of 1.126 AU, an eccentricity of 0.205 and an
orbital inclination of 6 degrees. Bennu has a mean diameter of 492 meters
(uncertainty: 20 meters) and a sidereal rotation period of 4.29746 hours
(uncertainty: 0.002 hours).
Bennu is a B-type asteroid characterized by a linear, featureless spectrum
with bluish to neutral slope at visible wavelengths. Spectral analysis
suggests that the most likely meteorite analogs for Bennu are the CI or CM
meteorites (Clark et al., 2011).
This shape model of asteroid (101955) Bennu was created by Nolan et al.
(2013) based on radar and optical photometric observations made in 1999
and 2005. The model resolution is approximately 25 meters between
vertices, with regions of higher resolution around the location of a
topographical 'boulder' and the symmetric region in the opposite
The model has the format
v x1 y1 z1
v x2 y2 z2
v x3 y3 z3
f i1 j1 k1
f i2 j2 k2
where the letter 'v' denotes a vertex and the letter 'f' denotes a
triangular facet. The VERTEX_TABLE is the first part, describing the
positions of the vertices of the shape model. The floating point numbers
x1 y1 z1 are the coordinates of vertex 1, and so on (vertices are
implicitly numbered beginning with 1). The origin is the center of mass,
and the axes are the principal axes of the shape model. The z-axis is the
spin axis or positive pole. The units are kilometers. The linking of
vertices into facets is provided in the FACET_TABLE.
The Asteroid (101955) Bennu Shape Model - 101955bennu.tab - file is
equivalent to the wavefront or .obj format. The file can be opened by
software such as Blender, MATLAB, JSC3D, or CAD programs, and can read
directly by most 3D printing services. A variety of free .obj viewers are
available for download online.
Multi-axis views of the model - bennu-model.pdf - is a .pdf of views of
the asteroid along its principal axes.
The Pole Orientation - pole.tab - file contains the pole latitude,
longitude, and uncertainty in degrees.
The Rotation State - rotate.tab - file contains the rotation rate and
uncertainty in hours.
Nolan, M.C., C. Magri, E.S. Howell, L.A.M. Benner, J.D. Giorgini, and 6
others, Shape Model and Surface Properties of the OSIRIS-REx Target
Asteroid (101955) Bennu from Radar and Lightcurve Observations, Icarus
226, 629-640, doi:10.1016/j.icarus.2013.05.028, 2013. [NOLANETAL2013]
Clark, B.E., R.P. Binzel, E.S. Howell, E.A. Cloutis, M. Ockert-Bell, and 2
others, Asteroid (101955) 1999 RQ36: Spectroscopy from 0.4 to 2.4 um and
meteorite analogs, Icarus 216(2), 462-475,
doi:10.1016/j.icarus.2011.08.021, 2011. [CLARKETAL2011B]
Hergenrother, C.W., M.C. Nolan, R.P. Binzel, E.A. Cloutis, M.A. Barucci,
and 11 others. Lightcurve, Phase and Color Photometry of the OSIRIS-REx
Target Asteroid (101955) Bennu. Icarus, 226, 663-670,
Krugly, Yu.N., I.N. Belskaya, V.G. Shevchenko, V.G. Chiorny, F.P.
Velichko, and 7 others, The near-Earth objects follow-up program: IV. CCD
photometry in 1996-1999, Icarus 158, 294-304, doi:10.1006/icar.2002.6884,
ARECIBO 2380 MHZ RADAR RECEIVER
ARECIBO PLANETARY RADAR TRANSMITTER
GOLDSTONE SOLAR SYSTEM RADAR RECEIVER
GOLDSTONE SOLAR SYSTEM RADAR TRANSMITTER
Confidence Level Overview
There exists some north-south symmetry in surface features of Benu.
Because of the nearly-equatorial viewing geometry, this is an artifact of
the radar data, and the varying degree of symmetry in different parts of
the object may result from variable rotational coverage.
As the asteroid rotates, the points on the equator move across the radar
images, but points at the rotation pole remain motionless (Green, 1968).
As a result, the Z dimension of the asteroid is less well determined than
the X- and Y-dimensions: 'squeezing' the model in the Z direction does not
change the radar images much.
This coordinate system should not be used to define a cartographic system,
as the principal axes are not uniquely determined due to the symmetry of
the shape in terms of longitude.
Uncertainties reported are 1-sigma, but for the shape parameters are
conservative and somewhat subjective. Formal errors in the X- and Y-
directions are of 10 meters, and in the Z-axis, 52 meters.
Nolan, M.C., Magri, C., Howell, E.S., Benner, L.A.M., Giorgini,
J.D., Hergenrother, C.W., Hudson, R.S., Lauretta, D.S., Margot,
J.L., Ostro, S.J., and Scheeres, D.J., Asteroid (101955) Bennu
Shape Model V1.0. EAR-A-I0037-5-BENNUSHAPE-V1.0. NASA Planetary
Data System, 2013.
We present the three-dimensional shape of near-Earth asteroid
(101955) Bennu (provisional designation 1999 RQ36) based on radar
images and optical lightcurves (Nolan et al., 2013). Bennu was
observed both in 1999 at its discovery apparition, and in 2005
using the 12.6-cm radar at the Arecibo Observatory and the 3.5-cm
radar at the Goldstone tracking station. Data obtained in both
apparitions were used to construct a shape model of this object.
Observations were also obtained at many other wavelengths to
characterize this object, some of which were used to further
constrain the shape modeling (Clark et al., 2011; Hergenrother et
al., 2013; Krugly et al., 1999).
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