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"The Kansas balloon is going up two days after the peak of the eta Aquarids. The meteor shower will be dying down by then, but it may be the best time to catch comet dust," explained Dr. John Horack of NASA's Marshall Space Flight Center. "Eta Aquarids hit the atmosphere at 140,000 mph and conventional wisdom says they lose most of their kinetic energy right away, about 80 km above the stratosphere. Then they drift slowly to the ground, kind of like a feather thrown from the top of a skyscraper. High altitude winds and the bouyancy of the particle affect how quickly meteoroids descend. They might not pass through the stratosphere until days after the shower's peak." 
Left: This image of Comet
Halley's nucleus was taken by the Giotto
spacecraft during a flyby on March 13, 1986.
Scientists estimate that about 10% of the surface
was boiling off into space. The stuff that boiled off
in this picture may one day be seen again during
an eta Aquarid meteor shower.
The meteoroid catcher scheduled to fly this Saturday includes 300 square centimeters of polyacrylic films, plus 30 square centimeters of silica xerogel. The xerogel is lower density than the polyacrylic material and probably more sensitive to lower velocity particles drifting slowly downward from higher altitudes. The polyacrylic films are denser and better suited to the capture of compact, higher velocity particles. "The chances of catching an eta Aquarid are slim," says Dr. David Noever, a NASA/Marshall scientist. "The meteor shower will be 20 to 50 times weaker than the '98 Leonids, and the debris stream hits the earth slightly south of the equator. But, if we do catch something it should be relatively easy to tell whether or not it came from Halley. In 1985 Giotto [a European Space Agency spacecraft] flew right by Halley's nucleus through a cloud of debris bubbling off the comet. It got data on particle sizes, density, chemical composition -- just about everything you need to ID a meteoroid from Halley." "Chemically speaking, a Halley meteoroid caught in the stratosphere won't look exactly like one from deep space," continued Noever. "All meteoroids experience a thermal spike (5-15 s) during deceleration in the atmosphere. Simply put, the fragmentary dust gets hot and some volatile elements boil away. This changes the internal chemical ratios. How long the heating lasts depends unpredictably on the particle size, density of both particle and atmosphere, entry velocity and entry angle. Despite these complications we think we know enough about volatile evaporation to make reasonable chemical comparisons with pristine Halley particles." 
Right: Kansas Near Space Project balloonists grapple
with a double Near Space Capsule during a launch earlier this year. The black-hatted figure
on the left is Lloyd Verhage, the KNSP project manager.
This weekend's adventure won't be the first science experiment carried aloft by the Kansas Near Space Project (KNSP). Since its inception in 1996 the KNSP has flown payloads to study cosmic rays, to test the response of microorganisms to the environment of the stratosphere, and to gather high-altitude meteorology data, among others. All the experiments were designed and executed by students and hobbyists. "Above 100,000 ft the air pressure is only 1% of that at ground level and air temperatures are approximately -60 degrees F," explains Lloyd Verhage, the KNSP project manager at Kansas State University. "These are conditions closer to the surface of Mars than to the surface of Earth. The air up there is too thin to refract or scatter sunlight, so the sky looks black rather than blue. What we see at these altitudes is close to what shuttle astronauts see from orbit." 
Left: The KNSP Asimov II Near Space
balloon in flight.
"My favorite experiment so far was the Flight of the Roachanauts," continued Verhage. "We sent several roaches in a plastic habitat to 84,000 ft. We know roaches can survive the winter, so felt that temperatures wouldn't be a problem for a short 3 hour flight. Unfortunately the insects returned dead. We're planning to repeat the experiments with improved habitats and monitoring to better understand what happened. Who says there is no risk to expanding the frontiers of science?" In February 1999 Verhage and collaborators set a new altitude record for amateur launched balloons -- 114,600 ft. The previous record of 111,000 ft, established by Sky Science Over Kansas, had stood since 1994. The KNSP benchmark didn't last as long. Three weeks later, in March 1999, a Colorado group set a new standard by sending a balloon to 121,000 ft. "We would like to recapture the record this weekend," said Verhage. "I want to reach 122,000 ft at least, and I'd say we have a better than 50% chance of making it." This weekend's flight will begin just after dawn when the meteoroid flux over the launch site is greatest (see the figure below). The balloon will take about 2.5 hours to reach 120,000 ft. At that altitude the balloon, which measures 8 ft across at sea level, will have grown in size to over 25 feet and it will pop. The descent by parachute takes about 1 hour. If all goes as planned the meteoroid collector will be recovered by Kansas Near Space Project personnel and returned to the Marshall Space Flight Center for analysis.  Above:The rate of meteor activity
is greatest near dawn because the earth's orbital motion is in
the direction of the dawn terminator. Earth scoops up meteoroids
on the dawn side of the planet and outruns them on the dusk side.
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The Kansas Near Space Project - home page Leonids' Particle Analyses from Stratospheric Balloon Collection on Xerogel Surfaces - conference abstract Leonids Live! -site of the live webcast of the 1998 Leonids Related Stories: |
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May 7, 1999: A group of educators and ham radio operators
known as the 
