Various stages of the thermophysical analysis used to attempt to reconcile the observed YORP acceleration with theoretical determinations. The pole-on shape model renderings were determined from imaging data from the Hayabusa spacecraft (Gaskell 2008), and highlight Itokawa’s “bi-lobed” appearance (Demura et al. 2006). Upper Left Panel – Average surface roughness distribution of Itokawa clones that produce a YORP rotational acceleration (or YORP spin-up). The roughness scale ranges from 0.45 (blue) to 0.55 (red). Lower Left Panel – Regular ellipsoids that interface at x ~ 150 m, with relative dimensions chosen for consistency with Scheeres & Gaskell (2008), which are loosely based on values from Demura et al. (2006). A density differential between the head and body can explain the COM offset. Upper Right Panel – Use of the true shape model with the interface between “body” and “head” regions of different densities at x = 150 m. Lower Right Panel – A compressed “neck” region of higher density located between the “body” and “head” to explain the measured COM offset. See Sect. 4 for details.