NCAR Flies Research Aircraft below Leonids Meteor Storm
Best opportunity in a century for observations
BOULDER--Two research aircraft carrying new scientific observing instruments and high-definition TV cameras will seize a once-in-a- lifetime opportunity to observe in stereo the Leonids meteors, expected to race at 160,000 miles per hour and bright as Venus into the Earth's upper atmosphere on November 17. An L-188C Electra, owned by the National Science Foundation (NSF) and operated by the National Center for Atmospheric Research (NCAR) in Boulder, will be joined by an Air Force KC-135 in the night skies over Okinawa, Japan, during the two-hour meteor storm. The Earth's orbit will cross the dense part of the tail of comet 55P/Temple-Tuttle, which produces the storm, presenting the best opportunity to take observations until late in the 21st century. NSF is NCAR's primary sponsor.
The National Aeronautics and Space Administration is heading the experiment, which is the first mission in NASA's Astrobiology Program, created to study the origin and prevalence of life in the universe. Peter Jenniskens, of the Search for Extraterrestrial Intelligence (SETI) institute and NASA Ames Research Center, conceived of and organized the experiment, called the Leonid Multi-Instrument Aircraft Campaign; it is also supported by NSF, the U.S. Air Force, and NHK Japanese television.
"What the return of Halley's comet was to comet studies, the return of a Leonid storm will be to meteor astronomy," says Jenniskens. "The Leonid showers' historic role cannot be overemphasized, but scientific observations have been very few."
The two aircraft are needed to raise the observing instruments into clear skies above the weather-laden lower atmosphere and to provide stereoscopic observations. The Air Force's FISTA (Flying Infrared Signatures Technology Aircraft) will circle the NSF/NCAR Electra in a racetrack pattern between 30,000 and 40,000 feet while the Electra flies back and forth (north-south) within the loop about 10,000 feet lower. At these altitudes (7 to 10 kilometers, or roughly 4 to 6 miles) both planes will be safe from the meteors above, which will burn up at 100- 120 kilometers (60 to 75 miles) above the ground.
The meteor storm will occur when the Earth enters the dense debris behind Temple-Tuttle on November 17, 1998, and again on November 18, 1999. Although the comet returns every 33 years, after 1999 Jupiter is expected to alter the comet's path, pulling its orbit further away from Earth during the comet's visits in 2031 and 2065. Scientists believe this year's passage is the best opportunity to observe the debris until the latter part of the next century. This crossing offers scientists a close look at the trails of unusually fresh and large (millimeter- to centimeter-size) material entering the earth's atmosphere at the fastest possible meteor speeds--72 kilometers per second (160,000 miles per hour). Best observations will be from East Asia (China and Japan). Next year, Europe and North Africa will offer the best viewing. From the ground, the source of the storm appears to be the constellation Leo.
A major scientific goal of the mission is to determine how a meteor's mass compares to its brightness. To date, scientists can only guess how much material enters the atmosphere during a meteor shower. To attack the problem, the Electra will carry a dual-beam lidar (laser-based radar) built this year to detect iron vaporized from the meteors in the upper atmosphere. Most meteors are rich in iron, which can be excited to fluorescence by the lidar's near-ultraviolet laser beams. The new instrument was developed by scientists and engineers from the University of Illinois, NCAR, and the Aerospace Corporation.
Also on board will be an airglow imager; several high-resolution visible-wavelength imagers; and NHK's intensified, high-definition TV cameras. Researchers will compare meteor brightness on the TV camera image to the iron density and temperature measured by the dual lidar to arrive at a brightness-mass correspondence. This may enable them to one day estimate the weight of a meteor shower from its brightness alone.
"The dual-beam lidar was built for the Electra, which provides an excellent airborne platform for this kind of study, " says NCAR project manager Bruce Morley. "We know very little about iron in the atmosphere and even less about the iron contribution from meteors. Observing just one meteor accurately from the sky would make a big difference to our understanding."
The Electra is a four-engine turboprop, modified and highly instrumented for atmospheric research. Participants flying on the Electra are from the University of Illinois at Urbana, the University of East Anglia (United Kingdom), NHK, and the SETI Institute. NCAR is managed by the University Corporation for Atmospheric Research, a consortium of more than 60 universities offering Ph.D.s in atmospheric and related sciences.
Electra Flight Schedule for Leonids98
Web Sites: For more information on Leonids98, see the following: http://www-space.arc.nasa.gov/~leonid/ During the mission, video animation and images will be available at: http://leonid.arc.nasa.gov
Note to Editors: Reporters are invited to the Jeffco Airport on November 5 to film Electra's departure and interview NCAR's Leonids project manager Bruce Morley.
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Last revised: Fri Apr 7 15:38:50 MDT 2000
Last revised: Thu Nov 12 09:29:18 MST 1998