Mystery Still Surrounds Iridium Debris Incidents

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PARIS — Two unexplained debris-producing events in 2014 involving active Iridium mobile communications satellites produced 14 pieces of identifiable debris whose source remains unknown, NASA’s Orbital Debris Office said Jan. 20.

In its quarterly assessment of space-debris developments, NASA’s Johnson Space Center in Houston said the two events, one in June and the second in November, “illustrate how mysterious many of the debris phenomena in Earth orbit still remain.”

McLean, Virginia-based Iridium Communications said after both incidents that the two satellites that NASA assumes produced the debris are working fine and recorded no anomalies on either occasion. Iridium satellites orbit at an altitude of about 781 kilometers.

NASA concludes the November event, which produced four pieces of debris following a low-velocity event, could have resulted from a small piece of junk striking the Iridium 91 satellite without upsetting the satellite’s orbit. Alternatively, it could have been “a sloughing off of insulation material that has been seen in other types of satellites before.”

The June event involving the Iridium 47 satellite produced 10 pieces of debris and is harder to explain, NASA said. “Some of these pieces were created with considerable delta velocity – in one case exceeding 80 meters per second. … [It] clearly was due to some sort of high-energy event.”

“In the absence of evidence of an explosion on board the spacecraft, a collision with a piece of untracked debris is the most likely culprit,” NASA concluded.