The recent
trials of an out-of-control communications satellite and a defunct, leaky
Soviet-era spacecraft toting its own nuclear reactor call up the question: What
exactly happens when satellites die in space?
There are
actually a few possibilities, some good, and others not
so much.
Bury the
dead
If mission
controllers spot a glitch in time, they can force a still-functioning satellite
to fire its engines and reach a so-called "graveyard orbit" a few hundred miles
above its initial flight path in order to safeguard its neighboring spacecraft
against possible damage.
That's what
engineers are trying to do for the telecommunications satellite Astra 5A, which
inexplicably failed on Jan. 15 after 12 years of operation. The satellite has
since been adrift
in space, moving out of its geostationary position about 22,300 miles (35,888
km) above Earth and is moving eastward along its orbital arc.
Astra 5A's owners, SES of Luxemburg, are pessimistic they'll
be able regain communications with the satellite and order it out to a safe orbit,
and have since warned the owners of other nearby satellites that they may need
to take measures to avoid an in-space collision.
Satellites
at the end of their lifetime have periodically been sent into graveyard orbits.
In 2006,
Russia's Express-AM11 communications satellite was moved to an orbital grave
after being hit by space debris.
Shoot it
down
In some
extreme cases, ailing satellites can be blasted
out space entirely.
Last year,
the U.S. military launched a missile from the Pacific Ocean that obliterated
the spy satellite USA 193. The missile destroyed the satellite, which was
plunging to Earth with a full tank of toxic hydrazine fuel, on Feb. 20, 2008.
Other
satellite shootdowns have not been so tidy. When China blasted an aging weather
satellite to bits in a 2007 anti-satellite test, the explosion generated a cloud
of orbital debris and sparked widespread criticism from other nations.
Watch
and see
Analysts
can also leave a problematic satellite to its own devices. That appears to be
the case with the Soviet-era
satellite Cosmos 1818. Launched by the former Soviet Union in 1987, Cosmos
1818 was the first of two satellites to test the use of advanced nuclear power
plants in space.
But this
month, NASA's Orbital Debris Program Office issued a quarterly update reporting
that Cosmos 1818 spewed a cloud of debris on July 4, 2008 that may have been
the result of leaking reactor coolant from a debris strike or fragmentation.
According
to a Thursday report by the Associated Press, Russia's Space Forces
chief Gen. Alexander Yakushin confirmed the fragmentation of Cosmos 1818, but
stressed it does not pose any risk of damaging the International Space Station
or raining radiation-contaminated debris on Earth because of its intentionally
high orbit. The satellite is breaking up in an orbit 500 miles (800-km) above
Earth - well above the 220-mile (354-km) plane of the space station - and its
status is being monitored daily, the Associated Press reported.
While
Cosmos 1818 appears to be under control, the same can't be said for Cosmos 954,
a Radar Ocean Reconnaissance Satellite (RORSAT) that spiraled out of control in
1978. The satellite re-entered the Earth's atmosphere and spread radioactive
debris across parts of Canada.
Fix it
or bring it back
Ailing satellites used to have a lifeline in NASA's space shuttles, which have
payload bays large enough to fit small spacecraft inside to be returned to
Earth or fixed in space.
The 18-year-old Hubble Space Telescope, for example, is one of the crowning
achievements of satellite resurrections. NASA astronauts have visited the
space-based observatory no less than four times, first to correct its blurry
vision, then to add new cameras and instruments that extended its mission.
NASA plans to launch the fifth and final servicing mission
to Hubble on May 12.
With NASA's space shuttle fleet slated to retire in 2010, sick satellites may
soon be visited by robotic surgeons. In 2007, the Pentagon successfully tested
flew a pair of spacecraft that demonstrated the ability to refuel and service
satellites robotically. The $300 million Orbital Express mission used a target
satellite and a robotic-arm wielding service vehicle to demonstrate autonomous
rendezvous and servicing tasks.
The
fiery plunge
One of the
more common ends for defunct spacecraft and garbage is death by cremation, in
which old spacecraft and debris are intentionally burned up in the Earth's
atmosphere.
Russia's
unmanned Progress cargo ships routinely end their spacefaring lives as
fireballs after delivering cargo shipments to the International Space Station.
The Russian Space Station Mir was also discarded in a similar funeral pyre in
2001.
Jules Verne,
Europe's first-ever Automated Transfer Vehicle, gave scientists a
spectacular light show when it ended its debut flight last fall in a fiery
blaze over the Pacific Ocean. Two chase planes were dispatched to record the
death of the spacecraft, which was as large as a London double-decker bus.
Some pieces
of debris don't burn up in controlled cremations.
Last
November, a tank of toxic ammonia the size of a refrigerator burned up over the
Southern Pacific Ocean more than a year after a spacesuit-clad astronaut
chucked it from the International Space Station. NASA did not know where the
tank would ultimately re-enter and the U.S. Space Surveillance Network tracked
the object to make sure its toxic remains did not endanger people on Earth.
Perhaps the
most memorable piece of U.S. space junk was the 77-ton Skylab space station,
which re-entered the Earth's atmosphere in July 1979, spreading debris across
areas of the Southeastern Indian Ocean and parts of Western Australia.
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