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(meteorobs) Threat To Spacecraft From Meteor Storm Said To Be Elevated But Not Serious
DIRECTORATE OF PUBLIC AFFAIRS
HEADQUARTERS
U.S. SPACE COMMAND
250 S. PETERSON BLVD, STE 116,
PETERSON AFB, CO 80914-3190
PHONE: (719) 554-6889 DSN: 692-6889
http://www.spacecom.af.mil/usspace
Release No. 98-26 October 6, 1998
Threat to Spacecraft From Leonid Meteor Storm Said to be Elevated But Not
Serious
PETERSON AIR FORCE BASE, Colo. -- The November 17 Leonid meteor storm will
present an elevated, though not serious, threat to spacecraft in the
vicinity of the Earth for about half a day, according to Department of
Defense and NASA experts who have been studying the potential risk to
spacecraft.
The annual Leonid shower -- this year a storm -- is expected to have an
intensity not seen in more than three decades. Even so, the event could
provide a dramatic "light show" for some parts of the world, particularly
East Asia and the western Pacific region.
The Leonid meteors originate from the debris released from the Comet
Tempel-Tuttle which completes an orbit around the Sun every 33 years,
leaving a trail of debris such as dust and other tiny particles. The Comet
passed perihelion, its closest approach to the Sun, early in 1998, setting
the stage for probable meteor storms in 1998 and 1999.
Conditions exist for encountering larger than normal numbers of meteors --
"shooting stars" -- streaking through Earth's upper atmosphere at rates of
thousands per hour. Leonid meteors will disintegrate upon entering Earth's
atmosphere and pose no threat to aircraft or the Earth's surface.
Leonid meteors travel at about 45 miles per second compared to about 12
miles per second for typical meteors. This risk of physical or electrical
damage to near-Earth spacecraft will be greater than normal.
Space operations crews have developed comprehensive strategies to limit the
potential effects of the storm. Crews have anomaly resolution procedures in
place that are based on years of experience and numerous recovery actions.
Several contingency plans exist that deal with specific anomalies for each
constellation of spacecraft.
NASA and the U.S. Air Force Space Command will conduct studies of the 1998
Leonid storm and will use these data in forecasting the potential 1999
storm.
Additional information on the expected Leonid meteor storm can be found on
the worldwide web at http://web99.arc.nasadot gov/~leonid/ and
http://www.spacecom.af.mil/usspace/leonid.htm.
Simple software to calculate the probability of impacts by Leonid meteors on
spacecraft in Earth orbit can be found on the worldwide web at
http://see.msfc.nasadot gov.
-30-
Donald Savage
Headquarters NASA, Washington, DC
(Phone: 202/358-1547)
Ed Campion
Johnson Space Center, Houston, TX
(Phone: 281/483-5111)
Major Perry Nouis
U.S. Space Command Public Affairs
250 S. Peterson Blvd, Suite 116
Peterson Air Force Base, CO 80914-3190
(Phone: 719/554-3525)
FACT SHEET
Threat Posed by the 1998 Leonid Meteor Storm
The Leonid meteors originate from the debris released from the Comet
Tempel-Tuttle which completes a path around the Sun every 33 years. Each
November the Earth passes through the plane of the comet, giving rise to the
Leonid meteor shower. When this passage occurs within a few years of the
comet's closest approach to the Sun, called perihelion, conditions for
encountering larger than normal numbers of meteors, i.e., a meteor storm,
may exist. Comet Tempel-Tuttle passed perihelion early in 1998, setting the
stage for a probable meteor storm in 1998 and perhaps again in 1999, as
jointly reported by the NASA Johnson Space Center's Orbital Debris Program
Office and the Air Force Deputy Chief of Staff for Air and Space Operations.
On November 17, 1998, the annual Leonid meteor shower is expected to arrive
with an intensity not seen for more than three decades. U.S. Government
agencies, led by NASA and the Department of Defense, have been studying the
potential risk of the Leonids to spacecraft in near Earth orbit out to the
L1 location, 1 million miles from the Earth toward the Sun. Projections are
the 1998 Leonids will not reach the levels of the 1966 meteor storm but will
present an elevated, though not serious, threat to spacecraft in the
vicinity of the Earth during a period of about half a day. However, the
'light show' visible in some parts of the world, particularly East Asia and
the western Pacific region, may be dramatic.
Due to the changes in the relative positions of the Earth and Comet
Tempel-Tuttle, Leonid meteor storms do not occur every 32-33 years. The
Leonids did not reach storm levels in 1900 or 1933, but did reach major
storm proportions in 1966. The 1998 outburst is likely to be much lower than
that observed in 1966. In fact, the stream of Leonid meteors for all sizes,
ranging from dust to sand-like particles, will probably not exceed the
typical daily meteor exposure. However, the higher velocity of the Leonid
meteors (~45 miles per second) as compared to the typical daily meteors (~12
miles per second) means the risk of physical or electrical damage to near
Earth spacecraft will be greater than normal.
The kinetic energy of a Leonid meteor will be 13-18 times that of a typical
meteor of the same mass. However, since the mass of Leonid meteors are
expected to be much less than that of typical meteors, the Leonids energy
level should be equivalent to normal exposure of a few hours to days. The
electrical discharge potential of the Leonids during the 12-hour period
centered around the peak activity may be equivalent to as much as months to
years of normal daily exposure.
Simple software to calculate the probability of impacts by Leonid meteors on
spacecraft in Earth orbit can be found on the worldwide web at
http://see.msfc.nasadot gov. For further information please contact Dr. Walter
Marker of the NASA Johnson Space Center at 281-483-0117 or
walter.marker1@jsc.nasadot gov or contact the Department of Defense focal
point, 14th Air Force Public Affairs at (805)734-8232.