When Orion gets near the moon, lunar gravity will pull the spacecraft to about 60 miles above the moon's surface. Mission controllers precisely fire the service module's engines, aiming for the exact altitude or height of a distant retrograde orbit. Orion travels for five days to meet the orbit, 40,000 miles beyond the moon. Once at just the right height, a second burn of the service module engines studies Orion into DRO. The orbit is called distant because Orion will be orbiting very high above the moon's surface. Retrograde is just a fancy word for opposite. The moon travels around the Earth in one direction. Orion will go around the moon in the opposite direction. DRO is a stable orbit that's easy for Orion to remain in. Once in the orbit, Orion will travel for six days around the far side of the moon, before making its way back to Earth.