will travel through space for the next nine months. its destination, a near-earth asteroid named ditamus and its moonlet. these asteroids are not a threat to the earth. that makes them an appropriate target for a first test. reporter: traveling at a speed of 6.6 kilometers a second, d.a.r.t. will then deliberately crash into the moonlet to try to jolt it from its regular orbit. scientists back on earth will monitor the collision using satellite imagery and ground-based telescopes to see how much the moonlet changes course. if one day an asteroid is discovered on a collision course with earth, then we have an idea of how big that asteroid is and how fast it s coming and when it will hit, that kind of information, we will have an idea how much momentum we need to make that asteroid miss the earth. reporter: the targeted moonlet is a little larger than