Where does airspace end and outer space begin? Space exploration has proceeded for nearly 50 years without a clear answer, but the increased use of spacecraft and satellites by many nations has spurred calls to define the boundary precisely. Harris and Harris argue that international law should establish a boundary based on the vertical distance from Earth's surface, rather than on more complicated functional criteria that could change as technology evolves. They note that airspace is heavily regulated and comes under the jurisdiction of sovereign nations, who have the authority to restrict airplane flight above their territories. In contrast, outer space is considered to be a public realm—described in the Outer Space Treaty as “the province of all mankind”—and an orbiting object is accountable to its owners and not to the countries beneath it. At the moment, orbiting satellites can be used to observe any country, whereas aircraft can be prohibited from doing so legally. Moreover, modern satellites can image the ground with meter-scale resolution, yielding pictures as sharp as those captured by a spy plane operating in airspace. A vertical boundary definition would promote discussion of the policy issues arising from technological progress. — JB
Space Policy 22, 3 (2006).