The Tropical Wind, Energy Conversion, and Reference Level Experiment, or TWERLE, was sponsored by the Goddard Space Flight Center (NASA) and designed and implemented by NCAR and the University of Wisconsin. TWERLE was an intensive program of meteorological observations made from superpressure balloons orbiting the earth at the 150mb density level. The balloons were tracked and monitored by the Nimbus-6 satellite, providing data which increased understanding of atmospheric circulation. Crew members at three sites in the tropic (Pago Pago in the South Pacific, Ascension Island in the Atlantic, and Ghana in West Africa) each launched about 100 balloons during the summer and early fall of 1975. The launch crews consisted of about five to seven NCAR staffers. A subsequent midlatitude phase, during which balloons were launched from Christchurch, took place from November 1975 to February 1976.