HIPPO 4

HIPPO Global Phase I took place in January 2009; Phase II in November 2009 and Phase III in April 2010. Phase V took place August 2011.

To accomplish the objectives of the fourth phase, the NCAR G-V flew the following missions:

• Rocky Mountain Metropolitan Airport, CO, USA -> Anchorage, AK, USA
• Anchorage, AK to the North Pole (up to 85 degrees North) round trip
• Anchorage, AK, USA -> Kona, Hawaii, USA with overflight of Cold Bay, AK
• Kona, HI, USA -> Pago-Pago, Am. Samoa or Rarotonga, Cook Islands (as a backup)
• Pago-Pago, Am. Samoa -> Christchurch, NZ
• Christchurch, NZ -> South Pole (up to 67 degrees South) recovering at Hobart, Tasmania 
• Hobart -> Darwin, Australia
• Darwin -> Saipan, North Mariana Islands
• Saipan -> Sand Island, Midway Islands
• Midway -> Anchorage, AK
• Anchorage, AK -> N. Pole round robin (up to 85 degrees North)
• Anchorage, AK -> Jeffco, Colorado

This 53,250 km long route differs from the Phase 1 route, which went via Eastern Pacific and had stopovers in Tahiti, Easter Island and Costa Rica. It is also different from Phase 2 route in not going over the Western Central Pacific. The Phase 3 route was also different from all others - direct North-South from Anchorage to Christchurch via Kona and Am. Samoa. The goal of Phase 4 was to sample air over the Western Pacific and Australia.

All of the flights were essentially direct point-to-point routes with ongoing altitude changes. It was planned to have 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 was conducted below RVSM (usually 28,000 ft) in order to allow the G-V to go up and down constantly to collect data at different altitudes throughout the troposphere. Ideally the flight would take off and go to FL430 for 15 min, then descend below RVSM and proceed in a sawtooth pattern between FL270 and FL100 with a 1,500 ft/min climb/ascent rate, then climb to FL450 near the end of the flight for about 15 min, descend and proceed 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 work schedule for details.