To gain a better understanding of the way life may have evolved on Earth, a team of scientists has begun a multinational airborne mission to study the Leonid meteors.
The Astrobiology mission began when two U.S. Air Force planes, the ARIA and the FISTA, lifted off from Edwards Air Force Base, Edwards, CA, on Nov. 13 at 11:15 a.m. (PT) enroute to Royal Air Force Mildenhall Airbase in the United Kingdom. During the mission, an international cadre of scientists will point their instruments towards the sky to study the Leonid meteors from the unique vantage-point of the aircraft.
"The planes provide a perfect platform for viewing the meteors," said Peter Jenniskens, chief scientist for the Leonids mission. "They lift us above the weather to ensure a fantastic view. By flying over 35,000 feet in the air, we are above most of the atmospheric water vapor, and our instruments get the best data possible."
The Leonid meteor showers occur each November when the Earth passes through the debris shed from periodic comet 55P/Tempel-Tuttle. The meteors, named the Leonids because they appear to stream from the constellation Leo, are about the size of a grain of sand. Studying comets and meteors, which are made from ice and dust that existed when the universe was formed, may help scientists develop a better understanding of how life began on Earth.
"Comets and meteors are fascinating to study because they are a frozen record from the time when the universe formed," explained astrobiologist Dr. Scott Sandford of NASA's Ames Research Center, Moffett Field, CA. "Due to geological activity, all of Earth's materials have been reformed several times over, and we must study comets, meteors and meteorites to get an early view of our universe."
Most years, observers with ideal viewing conditions can see 10 to 20 meteors per hour during the Leonid showers. Every 33 years when the parent comet Tempel-Tuttle passes particularly close to the Earth, as it did in 1998, meteor storms with hundreds or thousands of meteors per hour are possible. In 1998, following Temple-Tuttle's pass by Earth, counts of 250 meteors per hour were recorded. Predictive models have indicated that, in 1999, it may be possible to see 200 to 5000 meteors per hour around the longitudes of Europe and the Middle East. The 1999 Leonid Multi-instrument Airborne Campaign (MAC), a mission jointly funded by NASA and the United States Air Force, has been designed to fly over these longitudes for three consecutive observation nights, Nov. 16-18.
Both aircraft being used for the mission have been specially outfitted with a variety of instruments, including spectrometers and cameras, to study the meteors. The FISTA, an NKC-135 aircraft, has been modified with 20 upward-facing viewing ports. The ARIA, an EC-18 airplane, has telemetry equipment that will allow researchers to send images and near real time data regarding comet flux, or counts, to the ground.
Research objectives for the mission involve taking many measurements that have never been done in airborne astronomy, including real-time meteor counts, spectroscopy (mid-infrared, near-infrared, ultraviolet and visible) and stereoscopic viewing of meteors using intensified high-definition television cameras. The stereoscopic view, obtained when instruments on both aircraft image a meteor, will provide the first-ever three-dimensional model of meteor trajectories.
About half of the scientists on the current mission participated in the 1998 Leonid MAC mission that flew over Japan. That highly successful mission is credited with observing more than 3,200 meteors, obtaining the first differential spectrometry data from meteors as they burned through the sky, and obtaining the first stereoscopic images of a persistent meteor train.
After departing Edwards Air Force Base Nov. 13, the planes flew to Mildenhall Airbase in the United Kingdom. During the night-time crossing of the Atlantic Ocean, scientists tested and calibrated their instruments and completed initial observations, including taking measurements of the Aurora Borealis.
The mission will begin Nov. 16 when the planes depart England and fly the scientists overnight to Tel Aviv. The following night, Nov. 17, during the expected peak of the storm, the scientists will fly from Tel Aviv to Lajes Air Base in the Azores. The final night, Nov. 18, the planes will fly from the Azores to Patrick Air Force Base in Florida.
The peak of the storm is expected to occur at 0200 (UT) Nov. 18 (9:00 p.m. ET, Nov. 17) over Europe and the Middle East. While the best viewing of the storm will be in these locations, it may be possible to see the Leonid meteors in the United States, particularly in the predawn hours of November 17 and 18.
For current information about the Leonid MAC Astrobiology mission, visit: http://leonid.arc.nasa.gov/
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