[Prev][Next][Index][Thread]
(meteorobs) ACE Spacecraft Braces For Fierce Meteor Storm
Applied Physics Laboratory
Johns Hopkins University
Laurel, Maryland
Contact:
For ACE Spacecraft Design and Construction:
Ben Walker
JHU Applied Physics Laboratory
Phone: 240-228-6792 E-mail: Ben.Walker@jhuapldot edu
For ACE Mission Operations:
Jim Sahli
Goddard Space Flight Center
Phone: 301-286-8955 E-Mail: james.sahli.1@gsfc.nasadot gov
FOR IMMEDIATE RELEASE: 10 November 1998
ACE SPACECRAFT BRACES FOR FIERCE METEOR STORM
Like Key West store owners anticipating a hurricane, flight controllers at
the NASA Goddard Space Flight Center, Greenbelt, Md., are doing what they
can to prepare the 22 orbiting spacecraft under their command to meet the
November 17 Leonid meteor storm, predicted to be the fiercest in more than
three decades.
Each November 17 the Earth and its swarm of orbiting satellites passes
through the Leonid meteor stream, which originates from the wake of Comet
55P/Tempel-Tuttle. In most years the Leonid shower (so named because the
meteors appear to come from the direction of the constellation Leo) is
unimpressive. But once every 33-1/4 years -- this year - the Earth passes
through Tempel-Tuttle's path just after the comet has made its closest
approach to the sun, when dust, sand, and other materials have been freshly
boiled up from the comet's surface by the sun's radiation and left in its
trail.
NASA technicians are changing the orientation of spacecraft and ramping down
their high voltage supplies to reduce the risk of damage as they plunge
through the massive cloud of Leonid particles at a speed of 45 miles per
second for approximately six hours. They are maneuvering the Hubble Space
Telescope so its mirrors face away from the storm and adjusting other
spacecraft so their solar arrays will meet the storm "edge-on."
At most risk, scientists say, will be the Advanced Composition Explorer
(ACE) spacecraft designed and built by The Johns Hopkins University Applied
Physics Laboratory (APL), Laurel, Md. Launched in August 1997, ACE is in
orbit at a point 1 million miles from Earth toward the sun, a position that
will take it closest to the center of the comet's wake as we pass through.
ACE carries nine instruments designed to study energetic particles from the
sun, interplanetary space, and regions beyond. But none of these instruments
is designed to look at the tiny dirt and dust particles the spacecraft will
soon encounter. In fact, they'll be ducking their heads.
Mary Chiu, ACE Program Manager at APL, says, "We hope for the best, but we
really can't predict what will happen. The probability of getting hit by a
particle that could cause damage is still fairly small, but, depending on
the size of any given particle and where it might hit, the possibility for
problems exists."
To the extent possible, NASA will maneuver ACE so that the backs of solar
arrays will face the meteor storm and three of the most sensitive
instruments -- the Solar Energetic Particle Ionic Charge Analyzer, the Solar
Isotope Spectrometer, and the Cosmic Ray Isotope Spectrometer -- will be
pointed away from it.
"We're standing by to help the NASA team analyze and assess any problems
that might result from the storm," Chiu says. "But at the same time, we're
crossing our fingers in hopes for an uneventful day on November 17."
This dramatic encounter with the Leonid meteor storm will not be visible to
amateur stargazers in America, who, like sensitive instruments on NASA
spacecraft, will be on the back side of the Earth as it roars through the
cloud of particles.
The Applied Physics Laboratory is a not-for-profit laboratory and
independent division of The Johns Hopkins University. APL conducts research
and development primarily for national security and for nondefense projects
of national and global significance. APL is located midway between Baltimore
and Washington, D.C., in Laurel, Md.
To UNSUBSCRIBE from the 'meteorobs' email list, use the Web form at:
http://www.tiacdot net/users/lewkaren/meteorobs/subscribe.html