Skyhook balloons were balloons developed by Otto C. Winzen and used by the United States Navy Office of Naval Research in the late 1940s and in the 1950s for atmospheric research, especially for constant-level meteorological observations at very high altitudes. Instruments like the Cherenkov detector were first used on skyhook balloons.
In the late 1940s, Project Skyhook balloons provided a stable vehicle for long duration observations at altitudes in excess of 100,000 feet. Balloons, long used for collecting meteorological data, now offered the opportunity of collecting highly specialized information and photographs.
In 1948 Skyhooks were used to show that in addition to protons and electrons, cosmic rays also include high energy atomic nuclei that are stripped of their electrons. Thirteen stratospheric plastic Skyhook balloons were launched in September 1953 as part of Project Churchy, an Office of Naval Research funded cosmic ray expedition at the geomagnetic equator. The balloons encountered temperatures of -80°C (-112°F) during their flights which reached altitudes of over 100,000 feet.
On August 19, 1957, an unmanned Skyhook balloon lifted a cargo from the Stratoscope project, a program developed to research the sun. The main instrument was a 12-inch (30-centimeter) telescope with a special light-sensitive pointing system and a closed circuit television camera that researchers could guide—the first balloon-borne telescope. The telescope took more than 400 photographs of sunspots. These were the sharpest photographs taken of the sun up to that time. The photographs increased scientists' understanding of the motions observed in the strong magnetic fields of the sunspots.
The Skyhook ballon may be at the origin of UFO observations. The most famous case today involving the Skyhook was the Mantell UFO Incident.