The most dangerous debris on orbit includes big, derelict Russian rocket bodies and fragments from a 2007 Chinese anti-satellite test. In June 2025, a rocket body and a fragment passed within about 12 meters of one another, a leading space tracker said — not the most worrying close approach, but one that showcases low Earth orbit’s biggest threats.
The encounter was reported by Darren McKnight, senior technical fellow with California-based LeoLabs, in his biweekly newsletter highlighting close orbital approaches, or conjunctions. The size of a city bus and the weight of a large, African elephant, the rocket body carries the designation SL-16 R/B. The Chinese fragment is small, the size of a baseball or bigger, among the 19,000 pieces of debris tracked by U.S. Space Command. It comes from a Feng-yun 1C weather satellite deliberately blown up by a Chinese missile.
“First, the SL-16 R/B is the epitome of the intact derelict problem in low Earth orbit. It is massive … and was abandoned at 840 km where it will linger for centuries,” McKnight wrote. That’s the altitude around which some Earth observation, weather, communication and research satellites operate. “Second, the Feng-yun 1C breakup represents the most populous fragment cloud in LEO with over 3,500 fragments generated in 2007 of which nearly 2,400 are still in orbit.”
The conjunction occurred above the Atlantic Ocean, some 2,414 kilometers northwest of the African coast. The two objects approached at a near head-on angle at about 15 kilometers per second, close to 10 times faster than a bullet. The probability of a collision was 1.4%, McKnight said. Debris colliding in space can create more debris, depending on factors such as mass and speed, to endanger working satellites.
“Both objects were initially deposited in orbit in the 1990s, highlighting that much of the current debris-generating potential in LEO is due to actions taken last century,” McKnight said.