 There
are 88 of them weighing more than half a ton each, and they could
start falling toward Earth next month--chunks of them splashing
down in oceans and outbacks.
Not killer
asteroids, but $4 billion worth of Iridium global communication
satellites launched within the last five years--but for which
no one in the world can seem to find a use. Motorola Inc., the
system's largest backer, last week gave notice to a U.S. bankruptcy
court and to the Clinton administration that it is set to begin
the process of controlled "deorbiting" and destruction
of the network, which failed to attract many customers to its
telephone services.
The system
orbiting 485 miles high costs several million dollars a month
to maintain, according to the company.
Motorola
officials have declined to discuss their deorbiting plan until
they complete what spokesman Scott Wyman called "voluntary
and courtesy reviews" with government agencies. There are
also continuing last-ditch bids to save the network.
If the 53
tons of Iridium cast-offs find no savior, they will join a rain
of junk that has been peppering Earth throughout much of the space
age. Officials say the Iridium hardware is within government guidelines
for acceptable risk: less than a one in 10,000 chance of hitting
a person on the ground.
But the risk
is not zero, experts note. Not all of the Iridium components will
burn up during the fiery reentry through the atmosphere. The largest
hardware likely to survive the trauma and make it to Earth's surface
is the 2-by-3-foot titanium fuel tank.
Most of the
surviving chunks are expected to plunge into one of the oceans
that cover two-thirds of the planet. Those that strike land have
a good chance of dropping into remote, uninhabited areas. Officials
point out that no one in the space age has yet been harmed by
a piece of incoming space junk.
"It's
still a big world," said a government orbital debris expert.
"And even 6 billion people don't cover much of it."
He said the
Iridium fuel tanks "are not atypical" in size and mass
for spacecraft debris. Delta rocket stages, he added, reenter
regularly with much larger stainless steel tanks, one of which
landed outside Austin in January 1997, with no ill effect. In
space, astronauts have maneuvered the space shuttle several times
to avoid a collision with a piece of junk hardware, and the new
international space station was diverted in order to avoid a head-on
last October.
Although
there are larger satellite constellations aloft than the Iridium
system, he said, no one has decommissioned all their craft to
reenter the atmosphere in such numbers.
U.S. policy
calls for satellite makers to remove defunct objects from orbit
within 25 years in order to minimize the growing accumulation
of old rocket bodies and other detritus. The U.S. Space Command
is tracking about 9,000 orbiting manufactured objects four inches
across or larger. By controlling the reentry and timing the final
thruster firings properly, experts say, the ground team can maximize
the chances the hardware will hit empty ocean. "There are
controlled robotic ballistic reentries that are done with a high
degree of accuracy," said one specialist.
The National
Aeronautics and Space Administration (NASA) last June, for example,
made a controversial decision to deorbit the 17-ton Compton Gamma
Ray Observatory in this fashion, rather than waiting until it
deteriorated into a less controllable state. Aware that too many
pieces would survive reentry for the craft to meet the government
safety standard, controllers at Goddard Space Flight Center in
Greenbelt successfully guided the craft into the eastern Pacific.
Participants
in the seven-month government review of Motorola's deorbit plan
include the White House science office, Justice Department, NASA,
Federal Aviation Administration, Federal Communications Commission,
and security and economic officials.
The electronically
linked network of Iridium satellites, operated by the now-bankrupt
Iridium LLC, was designed to permit any type of telephone transmission--voice,
paging, fax or data--to reach its destination anywhere on the
planet, using either a cell phone or land line. The system made
its commercial debut in 1998 but suffered from marketing mistakes,
technical problems, bulky telephones and competition from proliferating
land-based cell phone networks.
The system
found perhaps its greatest popularity among skywatchers fond of
glimpsing the occasional flash of sunlight reflected off one of
the craft as it passed overhead, a phenomenon dubbed "Iridium
flares."
In order
to function as advertised, the constellation required 66 satellites,
but the backup craft bring the total to 88. Of these, sources
said, there are 74 "active" ones and 14 craft that stopped
functioning after reaching orbit. The latter are expected to make
uncontrolled reentries into the atmosphere over the next 100 years
or so.
Thirteen
feet long, with a solar wing span of 28 feet, each satellite has
a "dry" (unfueled) mass of 1,215 pounds.
There is
still a remote chance that the costly constellation might be saved.
Senior federal
officials are involved in an eleventh-hour effort to rescue the
system, with revived interest being expressed by some of the players
involved in a major earlier bid, according to an informed source.
The federal role, he said, is to help resolve "some technical
glitches."
"I can't
say everything is hunky dory," said a government source familiar
with the negotiations. "But there is still hope."
There have
been about 30 expressions of interest to date, according to Motorola's
Wyman. He declined to comment on any one of them but said, "We
have been involved in no formal discussion with any parties in
recent days. . . . The track that we are on is to decommission
the system."
The latest
report that a California group had offered $30 million to acquire
the $5 billion system (including ground-based assets as well as
satellites) prompted gallows humor at one federal agency: a suggestion
that the Iridium system might end up for sale as a gift in the
Neiman Marcus Christmas catalogue.
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