BChinese ALTA Balloon Program
For a few years now DARPA has been playing with a concept for high altitude surveillance balloons using a technology called “Strat-OAWL.” Balloons have been fielded for centuries as surveillance weapons, but unpredictable wind and atmospheric changes push the balloons around, making them useless within a coupe of days for any specific region.
To break it down simply, Strat-OAWL is the experimental use of lasers to read wind speed and direction far ahead of a balloon. The balloon then uses that data to increase or decrease altitude to ride airstreams in whatever directing the military wants the balloon to go. This could allow increased navigational control, but the Holy Grail that DARPA seeks is a high alt balloon that can stay in one place indefinitely.