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Pop! Ping! Perseids!


A Perseid Meteor in 1995.
Credit: Northeast Florida Astronomical SocietyAugust 13, 1999: Skywatchers around the globe enjoyed a modest Perseid meteor shower during the predawn hours of August 12 and 13, 1999. Observers in Europe and North America reported seeing 40 to 60 meteors per hour around the time of the Perseid maximum.

While meteor enthusiasts were enjoying the shower from the ground, the Science@NASA meteor balloon was launched to film the Perseids from a vantage point in the stratosphere, over 100,000 ft above sea level. Unfortunately it was not to be. The latex balloon ruptured earlier than planned at 65,000 ft, 40,000 ft shy of the anticipated maximum altitude.

Right: On August 12, 1995 this Perseid meteor appeared as bright as a full moon and left a visible smoke trail that could be observed in binoculars for as much as 6-8 minutes. The 1999 Perseid meteors were numerous, but fireballs were rare. The meteors which made up this year's shower tended to be fast, brief, and no brighter than about 2nd magnitude. Image credit: the Northeast Florida Astronomical Society.

According to Ed Myszka, an engineer who built the meteor balloon payload, the balloon popped not long after passing through the tropopause. The rapid change in temperature at that layer of the atmosphere caused the latex membrane to become brittle and it ruptured.

"We had a bit too much helium in the balloon for this payload and flight profile," explained Myszka, "but we learned something and that's important. This flight was really intended to be an engineering test to prepare for the 1999 Leonids. We flew a new GPS telemetry system, a new CCD video camera, and some new meteoroid capture media. Aside from the balloon bursting early, everything worked like a champ!"

Above: A RealVideo replay of the balloon popping may be viewed by clicking here. It is a five minute segment of the Perseids Live! webcast beginning at 17,116 m. The gurgling sounds during the first 3.5 minutes are caused by high altitude winds blowing past the balloon's onboard microphone. John Horack can be heard providing a voice-over commentary about the flight and the Perseids meteor shower. Three minutes and thirty-nine seconds into the replay, at an altitude of 18,898 m, the balloon pops. The rupture itself was relatively soundless, but you can immediately hear the gurgling sound transformed into a screech of rushing wind as the payload plummets toward the earth.

Myszka says that there will probably be at least one more round of engineering tests before the November Leonids, but that the Perseids flight has already verified many of the payload's critical subsystems.

The balloon descended by parachute from 65,000 ft and landed in a cow pasture near Huntsville, Alabama. Ed Myszka contributed this account of the payload recovery:

"Several of us found the package, which had landed in the corner of a pasture area, by tracking its GPS signal. While we debated waking the owners at 04:45 a.m., they walked up from their house to see what was causing their dogs to create such a commotion, and to further investigate the 'beepin noise' that had started about an hour earlier. Once we explained who we were and what we needed, they gave us permission to retrieve the package from their property. The payload was intact with no visible damage, except for a crushed antenna that was damaged on landing."

Meteor Pings

While most observers looked for the Perseid meteors with their eyes, some enthusiasts used ham radios to listen to the shower. When fast-moving meteoroids strike Earth's atmosphere they heat and ionize the air in their path. The luminous ionized trails are not only visually striking -- they also reflect radio waves. During a major meteor shower such as the Perseids, radio signals from TV stations, RADAR facilities, and AM/FM transmitters are constantly bouncing off short lived meteor trails. Whenever a meteor passes by with the correct geometry, listeners hear a brief "ping" on the receiver's loudspeaker.

Left: Stan Nelson points his radio antenna toward the Navy Space Surveillance transmitter in Texas.

In New Mexico on August 12, 1999, Stan Nelson monitored 217 MHz transmissions from the Navy Space Surveillance Radar located in Lake Kickapoo, TX. The Perseids shower was scheduled to peak at about 2 p.m. in Nelson's time zone while the sun was still out. The bright sunlight, which would be an impediment to visual observers, didn't stop Nelson from detecting the Perseids on the radio. He recorded 30 meteor radar reflections during an interval lasting just over a hour.

Click to hear a Perseid radar "ping"!
700 kb WAV file, courtesy Stan Nelson

It's not over yet

If you missed the Perseids shower on August 12 and 13, don't worry, the shower continues at a lower level until August 22. You can watch the action by following the simple observing tips explained in a previous Science@NASA headline, "Here Come the Perseids!" Web Links

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Perseids Live! -site of the live webcast of the 1999 Perseids


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For more information, please contact:
Dr. John M. Horack , Director of Science Communications
Author: Dr. Tony Phillips
Curator: Bryan Walls
NASA Official: John M. Horack