A European space satellite that has
been mapping the Earth's
gravitational field is set to crash
down to Earth in the coming days,
and it could provide a "real treat"
for space watchers.
But could GOCE (pronounced "GO-
chay"), which is set to make an
"uncontrolled entry" into the
atmosphere, present a risk to
anyone on the ground?
"For the most part, these
uncontrolled re-entries are the
norm," Space.com's Tariq Malik told
Yahoo News in a phone interview.
"It's not so much that we've been
lucky to not get hit by one as it is
the planet is so big."
The European Space Agency does
not know exactly when GOCE, short
for Gravity field and steady-state
Ocean Circulation Explorer, will
crash to Earth, and experts there
don't know exactly where it will
land. But the general consensus is
that it will re-enter Earth's
atmosphere sometime between
Friday and Monday.
"It's rather hard to predict where
the spacecraft will re-enter and
impact," the ESA's Rune
Floberghagen told the New York
Times. "Concretely our best
engineering prediction is now for a
re-entry on Sunday, with a
possibility for it slipping into early
Monday."
And if all goes well, people may be
able to watch the satellite safely
enter the atmosphere and explode
into a fireball of smaller fragments.
"The one thing I'm really wondering
about is where the re-entry might
be visible from," Malik said. "It's
very instructive to watch this stuff
burn up. From the ground, it's like
watching a giant fireball. If that
happens, viewers on the ground
could really get a treat."
So far, the odds have worked out
incredibly well for people on Earth.
No known satellite has ever
impacted a person or destroyed a
significant piece of property.
However, that doesn't mean space
junk hasn't come close to civilization
before. In 1979, fragments from the
first U.S. space station SKYLAB
landed in Western Australia , though
no one was hurt in the impact. And
in 2004, NASA's Genesis satellite
crashed into the desert in Utah
when its parachute failed to deploy
on re-entry. And again, even though
the impact created a crater, no
person or private property was
harmed by the impact.
And it was estimated last year that
ENVISAT, the largest satellite in
history, could pose a 150-year threat
to Earth. Having run out of fuel, no
one knows when the 17,636-pound
satellite will return to Earth and
what kind of impact it might have.
Malik says that within about 24
hours of GOCE's re-entry observers
should have an accurate estimate of
when it will enter the atmosphere.
Then, within about 12 hours of its
re-entry, scientists will begin to
more closely predict where
fragments from the satellite will
land.
"It will start off as wide as a
continent or an ocean," Malik said.
"By the end, nearly all of the
possible trajectory lines will have
been eliminated and they'll have a
good idea of where it's headed."
But even though it's extremely
unlikely that GOCE will pose a risk
upon re-entry, Malik still says any
would-be collectors would be wise to
leave any found debris alone.
"It's not really wise to touch it, even
though it's fallen down from space,"
he said. "It was powered by an
engine and you don't know what
kind of chemicals or residue are in
there."