Satellites, although not yet able to detect faces, can be used to detect if there is a possibility of a human in the areas like mountains, swamps and the like. Outlines of humans can be detected through satellite imagery. The military has been using satellites for years now to follow troop movements and other reconnaissance. Drones are also used to save manpower and are a good tool for surveillance. Drones can go wear men prefer not to. Like most things today, in some situations, I am not sure, but I would venture to say that the police may need a warrant to search using satellite technology.
There are well over 5000 satellites orbiting the earth. Not all of these satellites have this ability.