PARIS — The international space station required no collision-avoidance maneuvers in 2013, after a record four such moves in 2012, despite a growing orbital-debris population intersecting its orbit, according to NASA data compiled from the U.S. Space Surveillance Network (SSN) of ground- and space-based sensors.
NASA said the relatively quiet year from a debris-threat perspective reflects “the chaotic nature of the [debris] population,” which has forced the station to fire its engines to avoid a debris threat on 16 occasions in the 15 years it has been in orbit.
In addition to these 16 collision-avoidance maneuvers, one attempted maneuver failed and three others were never undertaken because the debris-proximity warnings came too late. In these three latter instances, the station crew was forced to retreat to the docked Soyuz spacecraft to be ready for an emergency undocking.
Collision avoidance means spending costly fuel to move a facility that is as big as a football or soccer field and weighs some 420,500 kilograms. Maneuver orders are given if there is a greater than one-in-10,000 chance of a debris strike.
SSN data show that the amount of debris that passes through the station’s orbit of 415-420 kilometers in altitude has increased by 60 percent since the first station module was launched in November 1998.
But that figure, now more than 800 objects with a mass ranging from less than a kilogram to more than 1,000 kilograms, includes only those objects that have been identified and cataloged by the SSN. The network has recorded some 5,000 other objects intersecting the station orbit that are awaiting entry into the master catalog.