In 1752, Ben Franklin used a key on a kite string to study
lightning. In 2002, NASA and university scientists devoted the month of
August studying the same phenomena – this time using a remotely piloted
aircraft soaring to heights of more than 50,000 feet.
Both experiments were “firsts,” offering new insight into dangerous
weather disturbances and what fuels them.
But today’s technology – the high-flying aircraft packed with
data-gathering instruments – enabled scientists conducting the Altus Cumulus
Electrification Study (ACES) to study electrical storms without the risks
Ben Franklin faced.
“Much has changed in 250 years since Franklin proved lightning
carries an electrical charge,” said the study’s principal investigator Dr.
Richard Blakeslee, a NASA atmospheric scientist at the Global Hydrology and
Climate Center in Huntsville, Ala. “Only recently have we acquired the
ability to get an up-close, comprehensive look at storms without risking
human contact with the energetic forces of nature.”
Based at the Naval Air Facility Key West in Florida, the
storm-hunter research team in August flew 11 science missions, making 115
passes over the tops of thunderstorms to gather a multitude of data that
will take months to fully analyze.
One of the study’s goals, Blakeslee said, was to test new aircraft
technology and determine its potential for future meteorological
applications.
“A challenge weather researchers often face is getting continuous
coverage of a single storm,” he said. “An aircraft flying at 200 mph, for
example, would provide only brief snapshots of storm activity sandwiched
between long periods with no observations.”
To overcome these challenges, the research team used the General
Atomics Aeronautical Systems, Inc. Altus II twin turbo uninhabited aerial
vehicle, often called a UAV. Chosen for its slow flight speed of 70 to 100
knots (80 to 115 mph) and high-altitude flight (up to 65,000 feet); the
Altus boasts a wing span of 55 feet and can monitor the storms on a
near-continuous basis.
“During this study, we made multiple storm passes in much shorter
time periods than ever before, proving it is possible to make nearly
continuous observations of severe weather,” Blakeslee said.
Evidence of this success was apparent Aug. 21, when the aircraft was
able to stay over and around a single storm for one hour and 20 minutes.
“For this one storm alone, we gathered data on more than 500 optical and
electrical events produced by lightning flashes,” he said.
“We gathered a vast amount of scientific information throughout
August, and each flight taught us something new about the aircraft’s
capabilities,” said project manager Tony Kim of NASA’s Marshall Space Flight
Center in Huntsville.
“The Aug. 21 flight was particularly noteworthy, because it was the
study’s longest-duration research flight. It lasted six hours and 32
minutes, enabling us to monitor four thunderstorms in succession. The final
storm had cloud tops at 50,000 feet, an altitude that would have made
studying this storm nearly impossible until recent advances in aviation.”
The results of this experiment help validate the use of remotely
piloted aircraft for atmospheric research as well as scientific research in
other areas. Part of NASA’s Uninhabited Aerial Vehicle-based, science
demonstration program, these flights acted as a proving ground for future
uses, such as carrying Earth-viewing scientific payloads into environments
where pilots would be exposed to potentially life-threatening hazards.
Data acquired during the research flights included electric,
magnetic and optical measurements, enabling the scientists to gauge elements
such as lightning activity and the electrical environment in and around the
storms. To complement this data, ground-based sensors gathered additional
information, such as the lightning flash rate, amount of precipitation and
speed of updrafts, while satellite imagery provided a view of the storms
from high above.
The team’s forecasting abilities played a key role in the
experiment’s success, with each day’s flight plan determined by predictions
of what the day’s weather would bring.
“Because we had to reach the storms while they were forming, good,
accurate storm forecasting was critical to our mission,” said Blakeslee.
“While we were often pleased with the forecasting information, there were
still times when the predicted weather did not develop as forecast. One of
our study’s goals is to help improve weather prediction.”
By learning more about individual storms, scientists also hope to
lend new insight into the global water and energy cycle and climate
variability, while providing federal, state and local governments with new
disaster-management information for use during severe storms, floods and
wild fires.
The Altus Cumulus Electrification Study is a collaboration among the
Marshall Center, the University of Alabama in Huntsville, NASA’s Goddard
Space Flight Center in Greenbelt, Md., NASA’s Ames Research Center at
Moffett Field, Calif., Pennsylvania State University in University Park and
General Atomics Aeronautical Systems, Inc. in San Diego.
The mission is part of NASA’s Earth Science Enterprise, a long-term
research effort aimed at understanding how human-induced and natural changes
affect our global environment, while providing practical societal benefits
to America today.
The Global Hydrology and Climate Center is one of seven science
research centers at the National Space Science and Technology Center (NSSTC)
in Huntsville. The NSSTC is a partnership with the Marshall Center, Alabama
universities, industry and federal agencies.
Photos
http://www1.msfc.nasa.gov/NEWSROOM/NSSTC/news/photos/2002/photosN02-007.html
Animations
http://www1.msfc.nasa.gov/newsroom/NSSTC/news/video/2002/videoN02-007.html
ACES Lightning Study Web site
