That landing will be rough. ROSAT rings the Earth once every 90 minutes. Its reentry speed will be some 17,400 miles per hour, though it will slow considerably as it enters the atmosphere. Moreover, it won't land in any one place. When UARS returned to Earth last month, two dozen pieces are believed to have scattered across a 500-mile swath of ocean. If ROSAT were to come down upon a populated land area, the impact points would be many.