NASA Meteor Balloon Rises Again
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NASA Meteor Balloon Rises Again
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.
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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. 
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!
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. 
Left: This photo from a laboratory
experiment shows the cone-shaped track made by a tiny high-velocity
particle in aerogel. The captured particle is located just beyond
the narrow end of the cone. Photo credit NASA/JPL.
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.
Leonids Live! -site of the live webcast of the 1999 Leonids
Related Stories:
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 |