CCNet DIGEST, 7 October 1998

    Andrew Yee <>

    E.P. Grondine <>

    Mike Baillie <>

    Bob Kobres <>

    Ron Baalke <>


From Andrew Yee <>

PETERSON AFB, CO 80914-3190
PHONE: (719) 554-6889   DSN: 692-6889

Release No. 98-26 October 6, 1998

Threat to Spacecraft From Leonid Meteor Storm Said to be Elevated But Not

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

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

Additional information on the expected Leonid meteor storm can be found on
the worldwide web at and

Simple software to calculate the probability of impacts by Leonid meteors on
spacecraft in Earth orbit can be found on the worldwide web at


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 For further information please contact Dr.
Walter Marker of the NASA Johnson Space Center at 281-483-0117 or or contact the Department of Defense focal
point, 14th Air Force Public Affairs at (805)734-8232.


From E.P. Grondine <>

     I note that several members of the Conference will be speaking
on the impact hazard at the Space Frontier Foundation annual meeting
to be held a few days from now in Los Angeles.  Having taken a
close look at these people before, and in concurrence with Perry and
Kiefer-Olsen, I'd like to suggest to those panelists that their
presentations should emphasize the following points:

1)  It shows a callous disregard for human life to advocate a manned
mission to Mars before adequate funding is insured for NEO detection
and the development of a planetary defense system.

2)  Due to the resources required for this enormous task, it will
have to be undertaken on a governmental level. Furthermore,the
problem is so large that the effort will have to be undertaken on an
international level.

3) No manned flight to Mars will be possible before it is determined
absolutely that Mars harbors no biological pathogens which present
a threat to life on Earth.

4) It will most likely be necessary to use nuclear charges to stop
Earth impactors, and therefore it will be necessary to see that these
are kept under some kind of international control.

Panelists may also be asked about the desirability of using Moon
based telescopes and radars to find smaller impactors. I know
opinions differ on this, but I point out that if you demand billions
you may succeed in getting millions.

                             Best wishes -


From Mike Baillie <>

I have noticed in a number of sources that Halley's computed return
time of 575 years for this comet is "known to be wrong".  However, I
have not yet noticed a source for this piece of information.  I'm sure
the readership will be able to enlighten me.  It seems interesting that
the very comet which Newton used to compute the conic section and which
Halley studied in some detail was actually not well understood by
either of them (?).

Mike Baillie
Palaeoecology Centre
School of Geosciences, Queen's University, Belfast
(01232) 335147


From Bob Kobres <>

From CNN Intercative

Research raises fear of dramatic  temperature change during warming

October 2, 1998

WASHINGTON (CNN) -- Ice core samples from Antarctica suggest that
the warming trend that ended an ice age 12,500 years ago may have
overtaken the Earth in only a few decades -- raising concerns that the
current warming trend may bring equally dramatic changes.

A University of Colorado team led by climatologist James White
will publish their findings in the journal Science on Friday.

Previous research had shown a simultaneous but even greater
increase in Arctic temperatures. Ice cores from Greenland, near
the Arctic Circle, show a temperature increase of almost 59
degrees within a 50-year-period.

And White's team said the Antarctica ice cores show a temperature
increase of about 20 degrees F within a few decades.

"What we see in Antarctica looks very, very similar to what we see in
Greenland,"  said White. "We used to suspect that some of these big
changes that occurred naturally in the past were only local. Since we
see the same thing at opposite ends of the Earth, it does imply that
the warming was a global phenomena."

He said the findings "throw a monkey wrench into paleo-climate research
and rearrange our thinking about climate change at that time."

White said researchers need to look more closely at how the Earth's
climate slipped  from an ice age that ended about 12,500 years ago and
shifted into the current, more temperate climate.

The findings, he said, also increases the urgency for researchers to
understand climate shifts because it appears they could be abrupt and
happen all over the Earth at roughly the same time.

Could we adapt?

"The challenge is to determine if a climate change will be a nice and
gradual thing that we can adapt to, or will it be a mode shift that
happens suddenly," said White.

The warming 12,500 years ago came within a typical human lifetime. Such
rapid shifts in the climate on a global basis would make it very
difficult for humans to adjust, he said. Climate affects agriculture,
energy use, transportation and population shifts, and rapid changes
would make adjustment in these things more difficult.

The Colorado researchers also found that the rapid temperature
increases prompted huge releases of methane.

Methane is one of the principal gases  responsible for the so-called
greenhouse effect, in which gases like carbon dioxide and methane form
a "blanket" around the Earth, entrapping solar heat and increasing
land, water, and air temperatures. Methane is a by-product of the decay
of plant matter.

Huge reserves of methane are trapped in frozen ground in the Arctic,
and researchers have speculated that a rapid polar melting could
release these trapped gases. Such methane releases would amplify the
greenhouse effect.

The Intergovernmental Panel on Climate Change, a global group of over
2,000 climate scientists, estimated in 1995 that the world should
expect temperature gains of 2 to 6 degrees by the year 2100,
potentially causing dramatic changes in weather patterns, severe storm
frequency, farm productivity, and enhancing the spread of tropical

Such a temperature rise would cause substantial melting of the polar
ice caps and would cause warming ocean waters to expand, raising sea
levels by up to 3 feet and obliterating low-lying lands.

The Colorado researchers' findings could suggest that the Earth is in
line for larger, swifter temperature changes. The new research does not
address how human activity could add to or impact climate change.

Sice 1980, 15 warmest years on record

The cause of the apparently rapid change that ended the ice age is
still largely unknown. A majority of climate scientists agree that
industrialization could be accelerating the current warming trend. 

But some scientists dispute the link between human activity --
primarily the use of fossil fuels -- and a steady increase in global
temperatures. They say that current record temperatures are simply part
of a centuries-long trend that is not a result of automobile and
factory emissions.

White said that global warming caused by man-made greenhouse gases may
be very similar to warming that may occur naturally.

"What humans are doing is in a way no different than what natural
systems do," he said. "Humans add methane to the atmosphere. So does
nature.. We are simply doing it faster."

For this reason, said White, studying natural climate change of the
past may give a fundamental understanding of how human actions could
change the climate in the future.

The 15 warmest years on record have occurred since 1980, with 1998 on
track for the highest average temperatures since record-keeping began
twelve decades ago.

Accompanying papers to be published in Friday's Science explore the
role of the oceans' currents in climate change. Columbia University
researcher Mark Cane suggests that ocean current changes may also
trigger long-term ice ages and warming trends, similar to the
short-term changes that produce El Nino weather patterns.


From Ron Baalke <>

The Deep Space 1 press kit is now available (PDF file - 1.5 MB):

Deep Space 1 is a technology demonstration mission scheduled for
launch near the end of October 1998.  The spacecraft will also
fly by asteroid 1992 KD in July 1999.

Ron Baalke

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