NASA Meteor Balloon Rises Again
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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.
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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.
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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."
Above: This time-frequency plot (or dynamic spectrum) shows two whistlers, one at 9 minutes and one at 12 minutes. They are caused by VLF radio emissions from lightning strokes that travel long distances along magnetic field lines. Other types of VLF radio emissions include tweeks, chorus, and spherics. To learn more about the physics of these emissions, click here. To hear what they sound like, click here.
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.
Right: This photo shows the payload from the 1998 Leonids meteor balloon after it was recovered from a briar patch in Chatsworth, Georgia on November 18, 1998.
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. Web Links
Leonids Live! -site of the live webcast of the 1999 Leonids
Leonids in the Crystal Ball -- Oct 27, 1999. Is 1999 the year for a Leonids meteor storm? Experts make their predictions.
Pop! Ping! Perseids! -- Aug 13, 1999. The Science@NASA meteor balloon popped before reaching the stratosphere but many meteor enthusiasts still saw and heard the Perseid shower.
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.
The Leonid Meteor Outburst of 1997 -- July 16, 1999.Newly released video shows a flurry of Leonids in 1997 that briefly rivaled the great meteor storm of 1966.
Leonids on the Horizon -- June 22, 1999. What's in store for the 1999 Leonid meteor shower? Experts make their predictions.
Hunting for Halley's Comet -- May 7, 1999. A high flying weather balloon ascends to the stratosphere in hopes of capturing an Eta Aquarid meteoroid
A Wild Ride to the Stratosphere -- Apr. 14, 1999. A weather balloon hits the stratosphere in search of meteoroids
Meteor Balloon set for Launch -- Apr. 8, 1999. This weekend scientists will launch a weather balloon designed to capture meteoroids in the stratosphere.
Leonid Sample Return Update -- Apr. 1, 1999. Scientists will describe initial results from a program to catch meteoroids in flight at the NASA/Ames Leonids Workshop April 12-15, 1999.
The Ghost of Fireballs Past -- Dec. 22, 1998. RADAR echoes from Leonid and Geminid meteors.
Bunches & Bunches of Geminids -- Dec. 15, 1998. The Geminids continued to intensify in 1998
The 1998 Leonids: A bust or a blast? -- Nov. 27, 1998. New images of Leonid fireballs and their smoky remnants.
Leonids Sample Return payload recovered! -- Nov. 23, 1998. Scientists are scanning the "comet catcher" for signs of Leonid meteoroids.
Early birds catch the Leonids -- Nov. 19, 1998. The peak of the Leonid meteor shower happened more than 14 hours earlier than experts had predicted.
A high-altitude look at the Leonids -- Nov. 18, 1998. NASA science balloon catches video of 8 fireballs.
The Leonid Sample Return Mission -- Nov. 16, 1998. NASA scientists hope to capture a Leonid meteoroid and return it to Earth.
Great Expectations: the 1998 Leonid meteor shower -- Nov. 10, 1998. The basics of what the Leonids are and what might happen on November 17.
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|For more information, please contact:
Dr. John M. Horack , Director of Science Communications
|Author: Dr. Tony Phillips
Curator: Linda Porter
NASA Official: M. Frank Rose