large satellites have collided in Earth orbit. It happened on Tuesday,
Feb. 10th at 1655 UT, when Kosmos 2251 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 were
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 apparently natural meteoroids:
LISTEN UP: The US Air Force Space Surveillance Radar is monitoring the
skies above Texas for echoes from satellite fragments. Try listening
on Thursday, Feb. 19th between 22:40 and 22:50 pm CST (0440 - 0450 UT
on Feb. 20th). That's when the main fragment of Iridium 33 is due to
pass over the radar. UPDATE: A Valentine's Day overpass of possible
Iridium 33 fragments produced this echo.
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