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 November 17, 1999: Astrobiologists
began their first airborne observation night to study the Leonid
meteors on Nov. 16, as the Earth began to enter the debris train
left by the periodic comet 55P/Tempel-Tuttle. At 21:50 GMT, on Nov. 16, the ARIA and FISTA, two United States Air Force planes, departed from Mildenhall in the United Kingdom for Tel Aviv Israel. During the overnight flight to Israel, the two aircraft flew approximately 80-100 miles apart from each other and as high as 38,000 feet. Above: This all-sky image of the 1998 Leonid outburst was obtained by the European Network in a 4 hour exposure from a location in the Slovak Republic. On other nights, a single meteor would have been a remarkable record. [more]
The scientists and crew members aboard the FISTA and ARIA had a very successful first night of their Astrobiology mission. In addition to observing meteors, the team took measurements of air glow, observed and recorded lightning over Spain, and saw Jupiter and Saturn clearly in the night sky. They also successfully demonstrated that live images of the meteors could be sent from the plane, over the TDRS satellite, to the Internet.
The science team on the FISTA was thrilled with the collected data. "By the end of this first mission night we have already exceeded the number of meteors we observed with our mid-infrared instruments during the entire 1998 mission over Japan," said Peter Jenniskens, Leonid mission chief scientist. The mid-infrared spectrographs, contributed by the Aerospace Corporation, are being used to detect the unique fingerprint of complex organic matter - like that required for life - in meteors. The instruments are also expected to provide information on the formation of solid particles and the heat of the meteors as they enter the atmosphere.  "A
total of 10 meteors crossed the field of view of our spectrograph,"
reported George Rossano, a researcher on the FISTA aircraft.
"I'm hopeful that these meteors will result in the first
successful mid-infrared fingerprint of a meteor." Left: This 400 KB QuickTime simulation illustrates the orbits of comet Tempel-Tuttle, Earth, and Jupiter from 1997-1999. The motion of the comet and planets are correct but their sizes have been exaggerated for clarity. Comet Tempel-Tuttle orbits the sun every 33 years and most recently passed near Earth in spring 1998. Like all comets, Temple-Tuttle is composed of ice and dust. As the sun slowly melts the ice, the comet's dust breaks off and spreads along the orbital path. Earth passes through Tempel-Tuttle's orbital dust field every November 17-18, causing the Leonids meteor shower. [click for animation] On ARIA, the flux measurement team counted meteors without actually looking out the window to see them; researchers wore goggles that displayed images from cameras that were pointed out of the airplane's windows. The number of Leonid meteors and sporadic meteors counted by each team member was entered into a laptop computer. Jane Houston, a member of the flux measurement team and one of several amateur astronomers on the mission, explained how the team differentiated between Leonid and sporadic meteors. "The Leonid meteors radiate from the constellation Leo, while sporadic meteors fall randomly across the sky." Each of the team members' laptop computers was linked to a central laptop computer, and near real-time data indicating the total number of meteors counted was provided. "The methods developed to count meteors for this mission could revolutionize the way future meteor showers are monitored," claimed Kelly Beatty, another amateur astronomer on the flux measurement team. At the end of the night, the flux team reported observing approximately 14 sporadic meteors per hour and a Leonid zenith hourly rate of approximately 15 meteors per hour. The zenith hourly rate is the number of meteors an observer on the ground would see under perfect observing conditions.  Right:
Anticipation of a 1999 meteor storm is based on an abundance
of historical accounts of Leonid storms which were used to map
out the distribution of all recent debris trails in the orbit
of comet 55P/Tempel-Tuttle by researchers Sekanina and Yeomans
(see figure above). During the upcoming Leonid encounters, Earth
will be at the right distance from the comet's orbit and far
enough behind the comet itself for rates to exceed 1000 meteors
per hour- perhaps ten times as much! This is a one-shot deal:
Earth will not cross that cloud during the next two returns of
the comet in 2031 and 2065. No other comet is known to have an
orbit as stable and as close to Earth's orbit. "These rates for Leonids are almost twice as high as those we would normally see the night before the expected peak," explained Dr. Jenneskins, "I'm optimistic this is an indication that we will see a good storm tomorrow night." The peak of the Leonid storm is expected at 02:00 GMT Nov. 18 over Europe and the Middle East. The international science team studying the Leonids will be flying from Tel Aviv to Lajes Airbase during the storm peak. It may be possible to see the Leonid meteor storm in the United States on the night of Nov. 17 (9:00 p.m. EST). However, best viewing may actually be in the predawn hours of Nov. 18. For more information about how to view the Leonids and submitting data to NASA, click here. The Leonid Multi-instrument Airborne Campaign is an Astrobiology mission from NASA Ames Research Center at Moffett Field, CA. The campaign is jointly funded by the United States Air Force and the National Aeronautics and Space Administration. Astrobiology is an interdisciplinary field that studies the origin, evolution, distribution and destiny of life in the universe. For current information about the Leonid Multi-instrument Airborne Campaign, and to watch live Leonid coverage on the Internet, visit: http://leonid.arc.nasa.gov/ |
| Web Links |
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Leonids Live! -site of the live webcast of the 1999 Leonids North American Meteor Network - home page Related Stories: Perseids
Live! Balloon Flight Planned
-- Aug 6, 1999. A NASA weather balloon will ascend to the stratosphere
for a live webcast of the 1999 Perseids. |
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