(off topic) Kachina, more stuff on meteor shower:
Meteor Storm Could Pose Threat To Earth Satellites
Date: 10/6/98
Author: Reinhardt Krause
(first El Nino, now a meteor storm???)
Satellite operators are bracing for a possible
onslaught from the heavens next month - a meteor storm
that may be the worst of its kind in three decades.
Serious damage to satellites and service disruptions
are unlikely, industry officials say. But satellite
operators are taking precautions to reduce possible
effects of the meteor onslaught, expected to last
roughly two hours on Nov. 17.
Scientists say the storm's intensity is unpredictable,
and the consequences may be dire. There now are 500
commercial and military satellites flying above the
Earth, compared with a few dozen in '66.
That's the last time this type of meteor shower,
called the Leonids, flared up to this degree.
''To knock a satellite off course, you really need
a large chunk of matter,'' said Peter Jenniskens, a
scientist at NASA's Ames Research Center at Moffett
Field, Calif., who will head a team studying the
meteor storm. ''What is of concern, though, are the
smaller grains, which can come in with a big punch.''
Meteor showers occur when the Earth travels through
clouds of particles left by a comet. In the case of
the Leonids, the dusty debris comes from a comet called
Tempel-Tuttle.
The Leonids bring annual meteor showers to Earth that
intensify into a stronger storm roughly every 33 years.
That's when Tempel- Tuttle visits the inner part of the
solar system. In these stronger storms, Tempel-Tuttle
sheds more matter.
While the Leonids meteor storm has been observed for
centuries, scientists aren't sure what to expect this year.
They do agree the coming storm should be the worst since '66.
Back then, the Leonids produced 150,000 meteors in an hour,
say Web sites devoted to the storm. That's about 7,000 times
its normal rate of 15 to 20 meteors per hour.
The difference between '66 and today lies in where the
Tempel-Tuttle comet passes through the solar system.
It whizzed by the Sun about 10 months ago.
The consensus among many astronomers is that the coming
storm won't be as bad as the one in '66. Current projections
estimate there will be as many as 10,000 meteors per hour.
But even computer models and high-powered telescopes come
up short in predicting the Leonids' intensity. This year
or next could spell trouble for satellite operators.
''We're not going straight through the comet's orbit,
but we might catch a cloud of debris,'' said William Ailor,
who heads the Center for Orbital and Re-entry Debris Study
at Aerospace Corp. El Segundo, Calif.-based Aerospace is a
nonprofit institute funded by the military.
Researchers don't expect particles from the Leonids storm
to punch a hole in a satellite's protective covering. One
reason is that most meteors typically are smaller in diameter
than a human hair. Larger objects are much less frequent.
But the particles are expected to whiz by at a speed of up
to 70 kilometers per second. That's about three times faster
than a run-of-the-mill meteor, or 1,700 times faster than
star pitcher Roger Clemens can throw a baseball, says NASA's
Jenniskens. The tiny particles could create an electrical
charge when smashing into a satellite.
''The more likely scenario is that these small particles
create charged (ionized) plasma at impact,'' Ailor said.
''That's like a small lightning strike that can cause
electronic problems within an aircraft.''
Still, most satellite operators are downplaying the Leonids'
threat. Greenwich, Conn.-based PanAmSat Corp. says it ''doesn't
believe the Leonids meteor storm poses a significant risk to
its satellites.'' With 16 satellites in orbit, PanAmSat is
the largest provider of commercial satellite services.
PanAmSat estimates the probability of an ''adverse collision''
at one-tenth of 1% for the duration of the storm. But in a
statement given to a congressional subcommittee in May,
PanAmSat left itself wiggle room.
''No assurance can be given by PanAmSat that its satellites
will be free of any effect or damage from the meteor storm,''
the company said.
PanAmSat already experienced poor luck this year. In May,
one of its satellites failed because of a short circuit.
That knocked out pager service throughout the U.S.
Which satellites could be most at risk in case the Leonids'
threat is real?
Naturally, the bigger the satellite, the higher the risk,
scientists say. One way to lower risk is shifting solar
panels to make a satellite's exposed area smaller.
Satellites with sensitive optics, like the Hubble Telescope,
may be more at risk.
''It depends from satellite to satellite what the concerns
are,'' Jenniskens said. ''The big issue in how dangerous
this is going to be is how many small grains there are in
the (meteor) shower.''
Other satellite firms are more upbeat about what will happen.
One is Intelsat, a global consortium that operates 24 commercial
satellites.
''We'll get our backup crews on the ground ready, on
stand-by to respond to anything,'' said Ahmet Ozkul, principal
scientist for satellite operations at Intelsat. ''But we aren't
overly concerned, and that's our message to customers.''
Iridium World Communications Ltd. and its partners have put
66 working satellites into orbit over the last year. In
September, Iridium delayed the commercial launch of its
global phone and paging services.
But Motorola Inc.-backed Iridium is in the final stages of
testing the system with a few thousand users. It should be
done in a month or so.
The Leonids storm isn't expected to disrupt Iridium's
services.
''I don't believe we are expecting anything, even though
it's a bigger shower,'' said company spokeswoman Michelle
Lyle. She adds that Motorola will move the angle of
Iridium's satellites to minimize risk.
(C) Copyright 1998 Investors Business Daily, Inc. |
