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The “Collaborative Research: HIAPER Pole-to-Pole Observations (HIPPO) of Carbon Cycle and Greenhouse Gases Study” measured cross sections of atmospheric concentrations approximately pole-to-pole, from the surface to the tropopause, five times during different seasons over a three year period. A comprehensive suite of atmospheric trace gases pertinent to understanding the Carbon Cycle was measured. HIPPO transected the mid-Pacific ocean and returned either over the Eastern Pacific, or over the Western Atlantic. The program provided the first comprehensive, global survey of atmospheric trace gases, covering the full troposphere in all seasons and multiple years. This phase of the HIPPO project was the first one of five.
To accomplish the HIPPO objectives, the aircraft flew the following missions:
This route is 44,700 km (27,760 miles, 24,200 nautical miles) long and took 21 days. Images below (courtesy of Google, GoogleEarth project) show the actual GV tracks.
All of the flights are essentially direct point-to-point routes with ongoing altitude changes. There were two maximum altitude ascents per flight, one in the first half and one in the second half, depending on the ability of the ATC to support altitude changes. Most of the flight were conducted below RVSM (29,000 - 27,000 ft in different FIRs) in order to allow the GV to go up and down constantly to collect data at different altitudes throughout the troposphere. Ideally the flight took off and went to FL430 for 15 min, then descended below RVSM and proceed in a sawtooth pattern between FL270 and FL50 with a 1,500 ft/min climb/ascent rate, then climbed to FL450 near the end of the flight for about 15 min, descended below RVSM again and proceeded to the airport.
All flights were followed by at least one no-flight, maintenance day and may be followed by a rest day ("hard down" day); see the flight reports table for details.