The Design Reference Asteroid for the OSIRIS-REx Mission Target (101955) Bennu An OSIRIS-REx DOCUMENT 2014-April-14 Carl W. Hergenrother1, Maria Antonietta Barucci2, Olivier Barnouin3, Beau Bierhaus4, Richard P. Binzel5, William F. Bottke6, Steve Chesley7, Ben C. Clark4, Beth E. Clark8, Ed Cloutis9, Christian Drouet d’Aubigny1, Marco Delbo10, Josh Emery11, Bob Gaskell12, Ellen Howell13, Lindsay Keller14, Michael Kelley15, John Marshall16, Patrick Michel10, Michael Nolan13, Bashar Rizk1, Dan Scheeres17, Driss Takir8, David D. Vokrouhlický18, Ed Beshore1, Dante S. Lauretta1 E-mail contact: [email protected] 1Lunar and Planetary Laboratory, University of Arizona, Tucson, Arizona 2LESIA-Observatoire de Paris, CNRS, Univ. Paris-Diderot, Meudon, France 3Applied Physics Laboratory, John Hopkins University, Laurel, Maryland 4Space Systems Company, Lockheed Martin, Denver, Colorado 5Dept. of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 6Southwest Research Institute, Boulder, Colorado 7Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 8Dept. of Physics, Ithaca College, Ithaca, New York 9Dept. of Geography, University of Winnipeg, Winnipeg, Canada 10Laboratoire Lagrange, UNS-CNRS, Observatoire de la Cote d'Azur, Nice, France 11Earth and Planetary Science Dept., University of Tennessee, Knoxville, Tennessee 12Planetary Science Institute, Tucson, Arizona 13Arecibo Observatory, Arecibo, Puerto Rico 14NASA Johnson Space Center, Houston, Texas 15Dept. of Astronomy, University of Maryland, College Park, Maryland 16SETI Institute, Mountain View, California 17Dept. of Aerospace Engineering Sciences, University of Colorado-Boulder, Boulder, Colorado 18Astronomical Institute, Charles University, Prague, Czech Republic Table of Contents I. Background on Bennu .................................................................................................... 5 II. Design Reference Asteroid ............................................................................................ 7 1 Orbital Properties ................................................................................................................... 8 1.1 Orbital Elements .............................................................................................................. 8 1.1.1 Reference Frame ...................................................................................................................... 10 1.1.2 Epoch Date (JD/ET) ................................................................................................................. 10 1.1.3 Epoch Date (Calendar Date/ET) ................................................................................................. 10 1.1.4 Semi-major Axis ...................................................................................................................... 11 1.1.5 Perihelion ................................................................................................................................ 11 1.1.6 Aphelion .................................................................................................................................. 11 1.1.7 Eccentricity .............................................................................................................................. 11 1.1.8 Inclination ............................................................................................................................... 11 1.1.9 Longitude of Ascending Node ................................................................................................... 11 1.1.10 Argument of Perihelion ........................................................................................................... 12 1.1.11 Mean Anomaly ....................................................................................................................... 12 1.1.12 Time of Perihelion (JD/ET) ..................................................................................................... 12 1.1.13 Time of Perihelion (Calendar Date/ET) ..................................................................................... 12 1.1.14 Orbital Period ......................................................................................................................... 12 1.1.15 Minimum Orbit Intercept Distance (MOID) .............................................................................. 13 1.2 Ephemerides ................................................................................................................. 13 1.2.1 Ephemerides ............................................................................................................................ 13 1.3 Positional Uncertainties ................................................................................................. 13 1.3.1 Positional Uncertainty Epoch (Ephemeris Time) ......................................................................... 13 1.3.2 Positional Uncertainty Epoch (Julian Date) ................................................................................. 13 1.3.3 Radial Position Uncertainty ....................................................................................................... 14 1.3.4 Transverse Position Uncertainty ................................................................................................. 14 1.3.5 Normal Position Uncertainty ..................................................................................................... 14 1.3.6 Radial Velocity Uncertainty ...................................................................................................... 14 1.3.7 Transverse Velocity Uncertainty ................................................................................................ 14 1.3.8 Normal Velocity Uncertainty ..................................................................................................... 15 1.4 Yarkovsky Properties ..................................................................................................... 15 1.4.1 Semi-major Axis Drift Rate ....................................................................................................... 15 1.4.2 Transverse Non-gravitational Acceleration Parameter .................................................................. 15 2 Bulk Properties ..................................................................................................................... 16 2.1 Size ................................................................................................................................ 20 2.1.1 Mean Diameter ........................................................................................................................ 20 2.1.2 Polar Dimension ....................................................................................................................... 20 2.1.3 Equatorial Dimensions .............................................................................................................. 20 2.1.4 Dynamically Equivalent Equal Volume Ellipsoid (DEEVE) Dimensions ....................................... 20 2.1.5 Volume ................................................................................................................................... 20 2.1.6 Surface Area ............................................................................................................................ 21 2.1.7 Projected Area at Equatorial Viewing Aspect .............................................................................. 21 2.2 Mass and Density .......................................................................................................... 21 2.2.1 Bulk Density ............................................................................................................................ 21 2.2.2 Mass ....................................................................................................................................... 21 2.2.3 Gravitational Parameter ............................................................................................................ 22 2.2.4 Area-to-Mass Ratio .................................................................................................................. 22 2.3 Global Models ................................................................................................................ 22 2.3.1 Global Shape Model ................................................................................................................. 22 2.3.2 Global Gravity Field Model ....................................................................................................... 22 2.3.3 Global Surface Slope Distribution Model .................................................................................... 23 2 2.3.4 Global (Tangent/Normal/Total) Surface Acceleration Model ........................................................ 23 2.3.5 Global Surface Tilt Model ......................................................................................................... 23 2.3.6 Global Surface Escape Velocity Model ....................................................................................... 23 3 Rotational Properties ............................................................................................................ 24 3.1 Rotation State ................................................................................................................ 24 3.1.1