Sinking Mir doesn't weigh down some sky watchers

(CNN) -- The rickety flagship of the Russian space program is poised for a plunge into the atmosphere. But some space scientists give little weight to fears about a rain of debris from the heavy orbiter.

Moscow plans to send the Mir space station to its end over the Pacific Ocean, prompting concerns that errant station chunks could threaten nearby nations such as Japan or Australia.

The 135-ton station is expected to make a fatal dive in about a week. Most of it should burn up, but Russian authorities expect more than 1,000 fragments to survive, including some the size of a small automobile.

GALLERY File pictures of Mir taken by astronauts aboard space shuttles   ALSO In-Depth Special: Mir falls to Earth   RESOURCES Check out this NASA satellite tracker Projected Mir re-entry path NASA's Mir tracker   MESSAGE BOARD Human spaceflight   ALSO

The heaviest object orbiting our planet other than the moon, Mir will become the largest spacecraft ever to return to Earth. Scientists who track large objects near our planet consider this information hardly the stuff of doomsday predictions.

"Asteroids weighing as much as Mir hit Earth perhaps 10 times each year," said NASA researcher Bill Cooke in a statement. "We know this because we observe the flashes of explosions in the upper atmosphere via Department of Defense satellites."

Some are even bigger. One year ago a 200-ton space rock ignited into a brilliant fireball as it broke up over the Yukon in Canada. Few pieces survived -- none was larger than several hundred grams.

Mir will be different. Chunks weighing up to 25 tons could survive, including everything from bolts to pieces of clothing to heavy metal bulkheads.

Solar panels and segments should rip apart from one another in the atmosphere. Pressurized modules will likely explode into incandescent fragments and streak across the sky. Passengers onboard an airplane chartered to chase the dying Mir hope to witness the spectacular fireworks.

"We expect Mir to break into six or more main pieces when it hits the atmosphere," said NASA's Nicholas Johnson in a statement. Johnson is the chief scientist for orbital debris studies at the agency's Johnson Space Center.

Sinking about 1 mile (1.5 km) each day, Mir had dropped to an altitude of about 150 miles (241 km) by Tuesday. Once it falls to within 137 miles of the planet, a series of thruster firings will position the orbiter for its final plunge.

The last suicidal burn should take place on or about March 20, pushing the craft though the atmosphere. Forty minutes later, Russian authorities hope, the remains of Mir will fall over a remote expanse of the Pacific between Australia and Chile.

Mir demise causes international high anxiety
March 6, 2001
Last rendezvous for Mir
January 27, 2001
Beginning of the end for Mir
January 24, 2001

NASA
Mir Home Page
Russian Space Agency

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