14, 2009) For the first time ever, two large satellites have collided
in Earth orbit. It happened on Tuesday, Feb. 10th at 1655 UT, when
crashed into Iridium
33 approximately 800 km over northern Siberia. The relative
speed of impact was about 10 km/s or 22,000 mph. Both satellites
to view a 2.3 MB animation
U.S. Strategic Command is tracking hundreds of satellite fragments.
Within days of the collision, the debris swarm spread around both
orbits. Experts characterize the distribution as a pair of "clumpy
rings"; one ring traces the orbit of Iridium 33, the other
traces the orbit of Kosmos 2251.
This injection of debris substantially increases the population
of space junk at altitudes near 800 km. Collisions are now more
likely than ever. Fortunately, the International Space Station orbits
Earth at a much lower altitude, 350 km, so it is in no immediate
danger. The Hubble Space Telescope is not so safe at 610 km. Researchers
are studying the make-up and dynamics of the debris to estimate
when fragments will begin to drift down to lower altitudes.
FIREBALLS VS. SATELLITE DEBRIS:
A series of bright fireballs observed in Texas, Kentucky and Italy
over the weekend of Feb. 13th were attributed by some news sources
to debris from the satellite collision. Not true. The fireballs
were natural meteoroids: full story.
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