Radar is how lots of asteroid imaging is done: https://en.wikipedia.org/wiki/Radar_astronomy#Asteroids_and_comets https://en.wikipedia.org/wiki/Radar_astronomy

Radar is how lots of asteroid imaging is done: https://en.wikipedia.org/wiki/Radar_astronomy#Asteroids_and_comets https://en.wikipedia.org/wiki/Radar_astronomy#Asteroids_and_... However, I wasn't aware of the optical methods mitchty was referring to.