Ancient satellite and rocket stage nearly collide in potential ‘worst-case scenario’

Conceptual image of space junk in Earth orbit.
Drawing: SCIPHO (PA)

An old rocket body and a military satellite – large chunks of space junk from the Soviet Union – nearly crashed into each other. Friday morning in an uncomfortable near miss that would have resulted in thousands of pieces of debris had they collided.

LeoLabs, a private company that tracks derelict satellites and objects in low Earth orbit, Point the near miss in the radar data. The company, which can track objects as small as 3.9 inches (10 centimeters) in diameter, operates three radar stations, two in the United States and one in New Zealand.

The two objects passed each other at an altitude of 611 miles (984 kilometers) on the morning of Friday January 27. LeoLabs “calculated a missed distance of only 6 meters [20 feet] with a margin of error of only a few tens of meters,” the company said in a Tweeter.

It’s incredibly close, as Harvard-Smithsonian astrophysicist Jonathan McDowell put it in a chart posted on Twitter. The body of the SL-8 rocket (NORAD ID 16511), more precisely its second stage, has been in space since 1986, while the military satellite Cosmos 2361 (NORAD ID 25590), known as Parus, has been launched into low Earth orbit in 1998. A collision between the two objects would have produced thousands of new debris fragments that would have remained in Earth orbit for decades.

The conjunction occurred in an orbit”bad neighborhoodlocated between 590 and 652 miles (950 and 1,050 km) above the surface, according to LeoLabs. This group has “significant potential for debris generation“in low Earth orbit” due to a mix of rupture events and abandoned derelict objects,” the company explained in a series of tweets. The so-called Bad Neighborhood hosts approximately 160 SL-8 rocket bodies along with their approximately 160 payloads launched decades ago. LeoLabs said about 1,400 conjunctions involving these rocket bodies have been reported between June and September 2022.

LeoLabs describe this type of potential collision between “two massive abandoned objects” as a “worst-case scenario”, saying it would be “largely beyond our control and would likely lead to a ripple effect of dangerous collisions”. Indeed, a collision on this scale would most certainly accelerate the ongoing Kessler syndrome, the constant accumulation of space debris that threatens to render parts of Earth’s orbit inaccessible.

Related story: What to know about Kessler syndrome, the ultimate space disaster

Near-misses in space are becoming more common, whether conjunctions between defunct satellites or clouds of debris threatening the International Space Station. Avoidance maneuvers are now commonplace for satellite operators, SpaceX, for example extreme, in front of perform more than 26,000 collision avoidance maneuvers of its Starlink satellites from December 1, 2020 to November 30, 2022.

In addition to focusing on collision avoidance, LeoLabs recommended implementation of debris mitigation and remediation efforts. This could take the form of sensible guidelines for the removal of satellites once they have been removed, as well as the introduction of debris disposal technologies.

Following: FCC wants 5-year deadline to de-orbit defunct satellites

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