Asteroid rotational rates became his speciality soon thereafter and by 1980, over 30 publications in Icarus with  Alan W. Harris resulted in nearly half of the (then) known rotational rates of these small solar system bodies.
Asteroid rotation rates became his focus, and by 1980, he published over 30 papers on this topic with Alan W. Harris, which resulted in a significant portion of the known rotational rates for these small objects in our solar system.