know the structure of the solar system. we have mercury, venus, earth, mars and there is a gap before you get to jupiter. in that gap is countless ast asteroids. most of them are. a sub set have a wayward orbit that brings them close to the orbit of the earth. in some cases they cross the orbit of the earth. 100% of these can be considered potentially hazardous. this targeted asteroid is a binary as a moon and we know precisely the orbit of that moon around the main asteroid. so when you slam into the moon and you slightly change its orbit, we know the orbit so well now, we'll be able detect what kind of change happened to it afterwards. >> so the amazing thing is this thing was launched overnight. it's going to smash into this asteroid in october of next year. you have to be pretty good at