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[Fwd: NASA Meteor Balloon Rises Again]





Ron Baalke wrote:

> NASA Meteor Balloon Rises Again
> Marshall Space Flight Center
> http://science.nasa.gov/newhome/headlines/ast01nov99_1.htm
>
> Scientists and radio amateurs team up for a live webcast of the 1999 Leonids
> from the stratosphere.
>
> Nov. 1, 1999: Last year when Science@NASA flew a weather balloon to the
> stratosphere for a high altitude view of the Leonids, over one million
> people watched the live webcast or saw the replay the next day at
> LeonidsLive.com. While the video camera on the balloon captured images of
> blazing fireballs, an aerogel collecting device may have captured bits of
> comet Tempel-Tuttle -- the parent of the Leonid meteoroid stream.
> Researchers are still poring over the data.
>
> Right: A short video segment showing a Leonid fireball as seen from the
> stratosphere in 1998. It was recorded by a digital video camera carried
> aloft by a 3m weather balloon.
>
> This year, with experts predicting an even bigger Leonid display, the meteor
> balloonists are planning another flight. Liftoff is scheduled for 0630 UT
> (0130 EST) on Thursday, November 18 from the Marshall Space Flight Center.
> The balloon will carry a sensitive low-light CCD video camera to monitor the
> shower from an altitude of about 32 km (105,000 ft), far above any obscuring
> clouds or bad weather. Web surfers can watch and listen to live
> transmissions from the balloon at LeonidsLive.com between 0130 and 0430 EST,
> on November 18th. Replays will be available after the flight.
>
> "We're going to be carrying a more sensitive camera than we did in 1998,"
> said Ed Myszka, an engineer and radio amateur who built the balloon payload,
> "so the images could be even better than before. The payload this time
> around will be similar to what we flew during the August Perseid shower. One
> of the problems we encountered during that flight was the balloon spinning.
> The camera was sweeping across the sky pretty quickly, which made it hard to
> see faint meteors. This time I've added ball bearing swivels to the lines
> between the balloon and the payload package. That'll reduce spin and make it
> easier to pick up meteors and fireballs during the webcast."
>
> An important addition to this year's payload is an INSPIRE VLF radio
> receiver, which is sensitive to radio emissions below 10 kHz. The very low
> frequency (VLF) radio band is filled with exotic-sounding signals called
> spherics, tweeks and whistlers. All three are impulsive bursts caused by
> distant lighting. "Spherics," which are caused by lightning strokes within a
> couple of thousand kilometers of the receiver, sound like twigs snapping or
> bacon sizzling on a grill. Tweeks and whistlers are caused by more distant
> lightning, and sound like brief descending musical tones.
>
> Dennis Gallagher, a plasma physicist at the Marshall Space Flight Center,
> thinks that the VLF receiver might also pick up natural radio emissions from
> the Leonid meteors.
>
> "Meteoroids produce an ionized trail as they plummet through the
> atmosphere," explained Gallagher. "There's a low density wake right behind
> the meteoroid. Because electrons are more mobile than protons, they move in
> to fill the void faster. That could set up plasma oscillations and trigger
> radio emissions."
>
> The VLF receiver was donated to the Marshall Space Flight Center for this
> and possible future flights by the Goddard INSPIRE program. It's been
> christened the "Marina receiver" after the newborn daughter of Flavio Gori,
> an Italian scientist who first suggested flying the receiver.
>
> Gallagher and his colleagues also plan to operate a Marina VLF receiver at
> the launch site to provide a ground reference for comparison with data
> collected from the stratosphere. During the flight signals from the receiver
> will be converted to audio sounds and transmitted along with images from the
> CCD video camera. Web viewers at LeonidsLive.com will be treated to an
> unusual combination of meteoritic sights and sounds.
>
> The question of radio emissions from meteors is an intriquing one, says
> Gallagher, and you don't need to send your receiver to the stratosphere to
> listen in. Anyone with a VLF receiver can monitor the Leonids on November 18
> and Gallagher hopes that INSPIRE participants across the USA will join in
> the effort. The best way to collect data is to record the output of the
> receiver on a two-track audio recorder. Record the VLF signal on one track
> and a WWV time signal on the other. This way VLF pulses can be correlated
> with the times of bright meteors seen from your observing site. It's also a
> good idea to conduct at least one observing session a few days before or a
> few days after the Leonids for comparison. Details about the upcoming meteor
> shower may be found at http://www.LeonidsLive.com.
>
> Catch a falling star....
>
> The video images and VLF sounds will be exciting, but the most important
> part of the payload may be something else entirely. The balloon will also
> carry aloft a special device designed to capture actual Leonid meteoroids
> and return them to Earth.
>
> Meteoroids are typically smaller than a grain of sand and much less dense.
> Although they are insubstantial, they can create very bright "shooting
> stars" because they travel at high speeds -- over 160,000 mph (72km/sec) for
> the Leonids. How do you catch a fluffy, microscopic, 160,000 mph fast ball?
> Very carefully!
>
> The meteoroid capture device on the upcoming flight uses xerogel (a close
> relative of aerogel) and a variety of low density acrylic materials to
> capture flying particles.
>
> "It works like flypaper," explains NASA astronomer Dr. John Horack. "We
> expose these materials to the air up in the stratosphere while the meteor
> shower is underway. When tiny particles strike the exposed xerogel, they
> stick. Then they return to Earth along with the rest of the payload."
>
> Aerogel is the lightest known solid, and is considered the best substance
> available for capturing fragile particles like comet dust without damaging
> them. When a high-velocity dust particle hits the aerogel, it buries itself
> in the material, creating a carrot-shaped track up to 200 times its own
> length. Since aerogel is translucent scientists can use these tracks to find
> the tiny particles. The track is largest at the point of entry, and the
> particle can be collected intact at the point of the cone.
>
> Experimenters agree that the chances of catching a Leonid meteoroid are
> slim, but that it's worth a try. Costing less than $4,000, the balloon
> mission could snag a tiny piece of comet Tempel-Tuttle (the parent of the
> Leonid meteoroid stream) and enable scientists to study material formed in
> the outer solar system.
>
> The balloon is scheduled to lift off from the The Atmospheric Research
> Facility (ARF) on the Marshall Space Flight Center (MSFC) Campus in
> Huntsville, AL at 0130 EST on Thursday, November 18. It will climb to a
> maximum altitude of approx. 105,000 ft in 200 minutes, followed by a
> 20-minute descent. Video and audio from the payload will be downlinked as an
> amateur TV signal at 426.25 MHz transmit frequency (Cable Ready TV Channel
> 58). The transmission should be detectable for several hundred miles around
> the launch site for readers who would like to directly monitor the flight.
>
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