While the spacecraft didn't know the hydrazine was about to run out, mission controllers had known for quite some time. As is typical for missions in deep space, Dawn operated most of the time out of radio contact. On Sept. 1 while coasting up, Dawn looked back at Ceres from an altitude of 2,220 miles (3,570 kilometers). Prominent on the limb, at a distance of 2,500 miles (4,030 kilometers), is Ceres' youngest cryovolcano, Ahuna Mons. Also during XMO7, Dawn provided scientists with more than three million infrared spectra and almost 50,000 visible spectra.