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Los Alamos Array Detects Large, Bright Meteor

Public Affairs Office (PAO)
Los Alamos National Laboratory
 
CONTACT: James E. Rickman, 505-665-9203 (97-155)
 
Los Alamos array detects large, bright meteor: Laboratory researcher joins
the search
 
LOS ALAMOS, N.M., Oct. 10, 1997 -- Researchers at Los Alamos National
Laboratory were able to use an array developed to listen for clandestine
nuclear weapons tests to help locate a large meteor that flashed in the sky
Thursday afternoon above Southern New Mexico.
 
The object -- presumably a large, bright meteor known as a bolide -- was
seen in the skies Thursday at about 12:47 p.m. Witnesses said the object
was at least as bright as the full moon or as bright as the setting sun.
 
"The meteor made a huge sonic signal," said Doug ReVelle, a meteorologist
in Los Alamos' Atmospheric and Climate Sciences Group. "They heard it
like a freight train in El Paso."
 
Using data from Los Alamos listening stations originally set up to monitor
nuclear explosions, ReVelle and other researchers in Los Alamos'
Atmospheric and Climate Sciences Group analyzed the infrasonic signature
created when the meteor entered the atmosphere.
 
When a meteor enters the atmosphere -- or when a large explosion is
detonated -- it creates a sound or pressure wave that is below the range of
human hearing. This infrasonic wave travels through the atmosphere and
can be detected by special microphones that are set up in an array. By
looking at the time of arrival of the sounds at different stations and the
frequency of the infrasonic boom, researchers can pinpoint the location of
the source and the determine the amount of energy that created it.
 
"The data from our array puts the meteor 441 kilometers due south of Los
Alamos," said ReVelle. "We'll be looking for it in a location we've identified
near El Paso."
 
ReVelle will join researchers from Canada, the University of New Mexico
and Sandia National Laboratory on a search this weekend for any meteor
fragments that may have reached the ground.
 
"The object's infrasonic signature was equivalent to the explosive yield of
about 500 tons of TNT," ReVelle said. "That means the object was
somewhere around one half to three-quarters of a meter in diameter."
 
Thanks to the infrasound array at Los Alamos, researchers at the
Laboratory were able to narrow down the location where it may have
landed pretty well.
 
In addition to searching for remains of the meteor -- which may have
exploded into tiny bits in the sky -- the researchers will interview witnesses
about the object: how bright it was; what it sounded like.
 
The object created a brilliant light as it streaked toward Earth. Witnesses
in Santa Fe, Los Alamos, Albuquerque, El Paso and points in between
saw the object in the sky.
 
ReVelle and the others will search all weekend for the object and collect
other data as well.
 
"It could take weeks to find, but it could take a day or less, depending on
how lucky we get," ReVelle said.
 
Infrasonic waves are very low frequency sounds that exist somewhere in
the realm between hearing and meteorology, ReVelle said. The sounds
are well below the range of human hearing, which ends at about 30 hertz,
but actually can be detected as small changes in atmospheric pressure. If
someone had a barometer that was sensitive enough, that person would
be able to see fluctuations of several microbars when infrasonic waves
arrive.
 
During the 1960s and early 1970s, before the rise of the satellite era, the
United States Air Force operated a network of stations to listen for nuclear
weapons tests. The listening stations were the nation's first line of
detection for nuclear explosions worldwide.
 
The four arrays of listening stations operated by Los Alamos are the only
infrasonic network left in full-time operation in the world. They can detect
meteors that are as small as a few centimeters in diameter. The stations
are useful because they can help validate other non-proliferation and
verification techniques, and they cost very little to operate and maintain.
 
The Los Alamos stations, around since 1983, still are enlisted in the
nation's nuclear non-proliferation efforts, but have provided a way for
scientists to detect bolides, larger-than-average space debris that slams
into Earth's atmosphere and creates brilliant fireballs in the sky.
 
Each year a number of large meteors enter the atmosphere and are
detected by the Los Alamos array. Some meteors are tens of meters in
diameter. ReVelle said each year about 10 meteors that are two meters in
diameter -- with an energy equivalent of a one-kiloton blast -- enter the
atmosphere. Most burn up or explode in brilliant flashes. Some hit the
ground.
 
For this weekend's search, ReVelle will join Peter Brown of the University
of Western Ontario; Alan Hildebrand from the National Research Council in
Ottawa, Ontario; a researcher from University of New Mexico's Institute of
Meteoritics; and Mark Boslough of Sandia National Laboratory.
 
Los Alamos National Laboratory is operated by the University of California
for the U.S. Department of Energy.