No, this is not science fiction. NASA's new'intruder alert' system, Scout, aims to identify asteroids heading towards Earth. A new NASA early warning "intruder alert" system should ease your fears. NASA's Scout computer program -- constantly fed by data from telescopes around the world -- watches out for potentially dangerous space rocks such as asteroids and comets, giving us early tip-off if one appears to be coming nearby. One rock was spotted just last week, which whizzed by Earth on Sunday night at a comfortable distance of 310,000 miles, according to NASA. This five-day warning may not sound all that impressive, but it's more than we used to have.