NASA's Global Hawk remotely operated aircraft No. 872 banks right over Edwards Air Force Base during a checkout flight. Preparations have begun for a multi-year NASA airborne campaign to study the humidity and chemical composition of the tropical tropopause over the Pacific Ocean in 2013-2014. (NASA Photo by Carla Thomas) › View Larger Image
Goddard Space Flight Center's Cloud Physics Lidar electronics are installed in the upper area of Dryden's Global Hawk unmanned aircraft just in front of the aircraft's communications antenna. (NASA Photo by Tom Tschida) › View Larger Image A consortium of scientists is in the early stages of preparation for a multi-year airborne science campaign being undertaken to study the humidity and chemical composition of air entering the tropical tropopause layer of the atmosphere, which extends from eight to 11 miles (13 to 18 km) above Earth's surface. This research will be conducted in 2013 and 2014 from three locations as part of NASA's Airborne Tropical Tropopause Experiment, or ATTREX, over the Pacific Ocean.
Studies have shown that even small changes in stratospheric humidity may have significant effects on climate as compared with the effects of decadal increases in greenhouse gases. Predictions of stratospheric humidity changes are uncertain due to gaps in the understanding of the physical processes occurring in the tropical tropopause layer.
Led by principal investigator Eric Jensen and project manager Dave Jordon of Ames Research Center at Moffett Field, Calif., the scientists are integrating instruments onto one of NASA's Global Hawk unmanned aircraft and verifying their operation during checkout flights made from Dryden.
Eleven instruments are being installed in equipment racks on Global Hawk No. 872. The instruments were initially tested during an Oct. 20 flight in the restricted area over Edwards Air Force Base, Calif.
On Oct. 28, the first of three long-duration flights headed west over the Pacific from Edwards, returning more than 21 hours later. The aircraft flew farther south than had any previous Global Hawk science mission, reaching 6.5 degrees north latitude.
The Diode Laser Hygrometer, developed by Langley Research Center, is mounted in the Global Hawk's payload bay in preparation for an atmospheric study of humidity and chemical composition. (NASA Photo by Tom Tschida) › View Larger Image The second long-duration flight - the 50th flight of a NASA Global Hawk - was a 16-hour mission conducted Nov. 5-6. A final Pacific Ocean flight was planned for Nov. 9 before the instruments are removed in mid-November.
The team consists of investigators from NASA, NOAA, three universities, the National Center for Atmospheric Research and private industry. The specialized instruments include a lidar, spectrometer, photometer, chromatograph, radiometer, hygrometers and several sensors used to collect atmospheric data. The science team will return to Dryden in January 2013 to begin the task of science data collection. The study will continue with deployments to the Pacific region in January and June 2014. Scientists hope to use the data to improve global model predictions of stratospheric humidity and composition.
Jensen's proposal for ATTREX was competitively selected. It is one of the first investigations in the new Venture-class series of NASA's low-to-moderate-cost projects announced in May 2010. The Earth Venture missions are part of the Earth System Science Pathfinder program. The small, targeted science investigations complement NASA's larger science research missions.