Aerospace Technology Development

Robotic Aircraft Used in Study

CHARACTERISTICS OF HIGH-LEVEL CIRRUS clouds that may affect global warming were measured over the subtropical Pacific for the first time in late April and continued through mid-May to help better understand climate changes and to build more accurate global climate models. Data from the study will help scientists better understand the dual roles of clouds—reflecting and absorbing solar energy—that are key uncertainties of global climate models used to predict climate change.

The measurements will help develop a global picture of how solar energy enters the atmosphere and moves within and through clouds. Clouds are effective at both reflecting incoming solar energy back to space and absorbing warm longwave radiation from Earth's surface, keeping that heat in the atmosphere, according to Dr. Peter Pilewskie, a Principal Investigator at NASA's Ames Research Center, Moffett Field, California.

Under a jointly funded Department of Energy-NASA atmospheric research project, data were gathered using specially designed instruments carried by a remotely piloted aircraft called Altus, flying at an altitude of 50,000 feet off the Hawaiian island of Kauai. The aircraft carried a 340-pound payload of radiometers, laser-based lidar detection devices and similar instruments to collect and transmit information about clouds.

A second aircraft, a DHC-6 Twin Otter, flies beneath the clouds in stacked formation with the Altus above, carrying radar from NASA that probes the ice and water content of the clouds. The remaining flights were carried out under a variety of conditions, with the unoccupied Altus controlled by pilots on the ground.

The Altus aircraft was built for NASA by General Atomics Aeronautical Systems, Inc. NASA's Dryden Flight Research Center, Edwards, California, provided the aircraft and is funding the flight series at the U.S. Navy's Pacific Missile Range facility. The climate studies are being guided by the Sandia National Laboratories for the Department of Energy's Atmospheric Radiation Measurement–Unmanned Aerospace Vehicle program.

The current series of flights by the Altus demonstrates the scientific and commercial potential of the remotely operated aircraft NASA is developing, according to Dr. James Stewart, manager of NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program at Dryden. This study marks the first time scientists have been able to get measurements from cirrus clouds with these instruments, according to Stewart, and may be the most successful flights that Sandia has flown while recording good atmospheric radiation data at these altitudes.

In the future, climate researchers would like to conduct similar measurements in a deep tropical region, closer to the equator, where tropical storms are responsible for bringing much moisture from the ocean into the atmosphere in a process that drives the dynamics of weather patterns far and wide. Once the dynamics are better understood, the climate models can reflect that understanding and improve forecasting.

Roughly 25 researchers from three Department of Energy laboratories, a dozen universities, three NASA centers and four private companies worked together at the Navy facility during the four-week mission. More information on the experiment is available at http://armuav.atmos.colostate.edu/uavs99/uavs99.html

For more information, contact Fred Brown at Dryden Flight Research Center.
Call: 805/258-2663, E-mail: Fred.Brown@dfrc.nasa.gov
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