The solar array is 4 km by 4 km. The whole Earth, with its 6400 km radius, only gets hit by a Prius-sized asteroid once per year. So the risks are much lower. I guess the array may be hit by many micro-asteroids though, but it should be possible to engineer some level of tolerance for that.
Yeah.. right after writing the comment I went on to get my frame of reference a bit adjusted about the sizes of everything...:) Risks are very small! So small that it's not even worth worrying about it too much. The whole cooling/heat transfer reality check is way more critical here than anything else indeed.
