Complex sentence: He has been a member of the Catalina Sky Survey (CSS) in Tucson, Arizona since September, 2005 and has discovered hundreds of Near Earth and main belt asteroids along with three comets.
Split into simpler sentences: He has been a member of the Catalina Sky Survey (CSS) in Tucson, Arizona since September, 2005. Since that time he has discovered hundreds of Near Earth and main belt asteroids along with three comets.