We mentioned in the figure caption that the alignments are simplified. One of the simplifications is that some of the orbits covered a range of angles. There is a well-understood and fully predictable natural tendency for the angle to increase. In some phases of the mission, the flight team allows that, and in others they do not, depending on what is needed for the best scientific return. At the lowest altitude (orbit 4 in the diagram, and sometimes known as LAMO, XMO1 or "the lowest orbit"), navigators held the orbit at a fixed orientation. Had they not done so, it would have changed quite dramatically over the course of the eight months Dawn was there. For XMO3, the team has decided not to keep the angle constant. Therefore, later observations will provide still different views. We will return to this topic in a few months.

We have described before how places that remain shadowed throughout the Cerean year can trap water molecules. Dawn’s pictures have revealed well over 600 craters high in the northern hemisphere that are permanently in darkness, covering more than 800 square miles (more than 2,000 square kilometers). (It has not been possible to make as thorough a census of the southern hemisphere, because it has been fall and winter there during most of Dawn’s studies, so some areas were not lit well enough. Now that spring has come, new photography will tell us more.)