1 of 10Image
After two decades in orbit, a 6.5-ton U.S. science satellite will plummet to the earth
on Friday evening, Sep. 23 or early Saturday, Sept. 24. NASA officials estimate 1,200 pounds of debris will survive the atmospheric re-entry, but are unsure where the plunging debris will
precisely hit. The latest projections show that North America is not in the line of fire.
Before relegated to space junk, the Upper Atmosphere Research Satellite (UARS)
collected data about the earth's atmosphere soon after astronauts aboard shuttle
Discovery deployed it in September 1991. The $750 million was decommissioned in
late 2005 and allowed to enter a phase known as orbital decay.
Falling orbital debris poses little threat to people and property on earth. In fact,
not many will witness the firework display that UARS will create as it falls back to
earth and the chances of anyone in the world getting hit by a piece of it is 1 in 3,200.
According to NASA, over the past 40 years an average of one cataloged piece of
debris fell back to Earth each day.
The real danger, however, is in space. Researchers have warned that space junk
floating around the Earth poses more of a threat than ever to spacecraft in orbit.
On the following pages are ten factoids about space junk that every stargazer, amateur astronomer,
or armchair satellite tracker should know:
It’s not just whole, abandoned satellites that constitute space junk. The term also
encompasses pieces of broken satellites, deployed rocket bodies, human waste,
tiny flecks of paint released by thermal stress or small particle impacts and other
random human-made objects. For instance, the glove lost by astronaut Ed White
during his historic 1965 spacewalk.
A swarm of at least half a million and possibly even tens of millions of pieces of space junk is currently circling the earth. NASA approximates 19,000 objects in Earth orbit larger than 10 centimeters, about half-million particles between 1 and 10 cm in diameter, and tens of millions of particles smaller than 1 cm. The most concentrated area for orbital debris is in low Earth orbit (LEO), the region of space within 2,000 km of the Earth's surface. The geosynchronous region (around 35,785 km altitude) also contains space junk, mainly weather and television satellites.