High-altitude balloons are unmanned balloons, usually filled with helium or hydrogen, that are released into the stratosphere, generally reaching between 60,000 to 120,000 feet (18 to 37 km). In 2002, a balloon named BU60-1 reached 53.0 km (173,900 ft).
The most common type of high altitude balloons are weather balloons. Other purposes include use as a platform for experiments in the upper atmosphere. Modern balloons generally contain electronic equipment such as radio transmitters, cameras, or satellite navigation systems, such as GPS receivers.
These balloons are launched into what is termed "near space"—the area of Earth's atmosphere where there is very little air, but where the remaining amount generates far too much drag for satellites to remain in orbit.
A seasonal vortex in Antarctica allows balloons to be recovered very close to their launch site, making it a popular location for balloon-based research.
Due to the low cost of GPS and communications equipment, high altitude ballooning is an emerging hobby.
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—Lynn Fontanne (1887–1983)