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