Meteor
Balloon Update:
The balloon was released at 6:47 p.m. CDT on Sunday April 11,
1999. It ascended to a maximum altitude of 95,000 ft where it
burst, as planned. The payload descended by parachute to a location
near Pinson, Georgia, landing at 8:37 p.m. A replay of the video
stream from the complete flight may be viewed here.
Apr. 9, 1999: On Saturday, April
10, NASA scientists will release a weather balloon designed to
capture cosmic meteoroids flying through the stratosphere. The
payload includes a xerogel microparticle capture device, similar
in some respects to the cosmic dust collector on NASA's Stardust
spacecraft, as well as a digital video camera to record a balloons-eye
view of the flight. Links to a live webcast of the flight will
be available at StarTrails.com.
Weather permitting, the launch will take place at 4 p.m. Central
Daylight Time on Saturday, Apr. 10.
Right: Artist Duane Hilton's concept
of the science balloon launched at dusk, ascending toward the
stratosphere.
Saturday's flight is part of a campaign by NASA scientists that
began with a balloon flight in Nov. 1998 during the Leonids meteor
shower.
"Last November's experiment went very well,"
says John Horack, a scientist at the NASA/Marshall Space Flight
Center. "Our engineering tests and video downlink were highly
successful, and the meteoroid collector hovered in the stratosphere
for nearly 2 hours during the peak of the Leonid meteor shower.
After we recovered the payload we looked at these xerogel collectors
with an electron microscope -- there were lots of tiny craters
caused by impactors measuring 20 to 50 um. We caught something,
but the question is 'What is it?' Did we catch meteoroids or
something else?"
Saturday's flight is intended to help answer that question. Unlike
last year's flight, which took place during the most intense
meteor shower since 1966, this mission coincides with an annual
lull in meteor activity.
"It's a simple control experiment," continued
Horack. "We've flown one balloon when the meteoroid flux
at the very top of the atmosphere was high, and now we're going
to fly another when the expected flux is low."
During the first quarter of every year there is a minimum of
meteor activity when Earth is relatively far from dense cometary
debris streams.
"Other than a few very minor showers, the only meteors to
be seen between January 15 and late April of each year are sporadics,"
says Dr. Tony Phillips, a NASA astronomer. "Sporadic meteors
are not associated with the debris stream from any particular
comet. They come from a diffuse, low-level background of dust
particles that permeates the inner solar system. On any given
night you can see a few sporadic meteors per hour, on average,
compared to hundreds of shooting stars per hour during an intense
Leonids shower."
The rate of meteor activity is greatest near dawn because the
earth's orbital motion is in the direction of the dawn terminator
(see the figure). Earth scoops up meteoroids on the dawn side
of the planet and outruns them on the dusk side.
"That's why we're launching the balloon near sunset,"
continued Phillips. "The body of the earth will act as a
shield, or a barrier between the balloon and most incoming meteoroids."
Readers
can also participate in this innovative experiment by counting
meteors on the evening of the balloon flight and reporting their
results back to the NASA Star Trails Society. Click
here for more information about how you can help. |
A remotely controlled video camera attached to the balloon
will record its ascent into the stratosphere. At first, the downward-looking
camera will show the earth, the horizon, and distant clouds as
illuminated by the setting sun. If all goes as planned, the 2
to 3 hour flight will continue after sunset and the camera will
be pointed to show the night sky as viewed from the stratosphere.
All video recordings will be transmitted to ground receivers
and rebroadcast live over the Internet. Links to the real time
webcast as well as replays after the flight can be found on www.StarTrails.com. |