That’s Long Dwell Time:

The Defense Advanced Research Projects Agency is working on two new types of unmanned surveillance aircraft, one that would ride on a ballistic missile and the other that could ride at very high altitude for five years or more, reports Scientific American. A 500-pound Rapid Eye would ride on board a missile that could deliver it to any spot on the globe within an hour and would deploy under its own steam to provide reconnaissance for at least seven hours without refueling. The Vulture would sustain itself at very high altitude possibly via solar energy and include a refueling capability, both of which would enable it to stay aloft over a target area for a very long, long time.