Data Set Overview                                                           
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    We observed near-Earth Asteroid (8567) 1996 HW1 at the Arecibo Observatory
    on six dates in September 2008, obtaining radar images and spectra. By    
    combining these data with an extensive set of new lightcurves taken during
    2008-2009 and with previously published lightcurves from 2005, we were    
    able to reconstruct the object's shape and spin state. 1996 HW1 is an     
    elongated, bifurcated object with maximum diameters of 3.8 x 1.6 x 1.5 km 
    and a contact-binary shape. It is the most bifurcated near-Earth asteroid 
    yet studied and one of the most elongated as well. The sidereal rotation  
    period is 8.76243 +/- 0.00004 h and the pole direction is within 5 degrees
    of ecliptic longitude and latitude (281, -31). Radar astrometry has       
    reduced the orbital element uncertainties by 27% relative to the a priori 
    orbit solution that was based on a half-century of optical data. Simple   
    dynamical arguments are used to demonstrate that this asteroid could have 
    originated as a binary system that tidally decayed and merged.            
                                                                              
    The shape model is presented as a faceted solid in Wavefront .obj format. 
    Also given are rendered .png images of the shape and tabulated rotation   
    state.

Confidence Level Overview                                                   
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    See table 3 of Magri et al., 2011 for formal model uncertainties. The     
    coordinate system is not precisely aligned to the center of mass and      
    moments of inertia. In principle, offsets could be physically meaningful, 
    but they are within the uncertainties for this model.