On Christmas Day 2013, a relatively small Russian rocket was launched from Plesetsk in the north of the country. The mission carried three small military communications satellites, but observers noted that the mission appeared to eject a fourth object into orbit.
Several months later, the Russians confirmed that this object was a satellite, and it became known as Cosmos 2491. To the surprise of many sky watchers, the satellite then began to perform new orbital maneuvers, such as raising and lowering its orbit, indicating rendezvous and approach operations.
Then, something similar happened again. In May 2014, another rocket booster brought three communications satellites into orbit as well as a fourth object, which was named Cosmos 2499. Finally, it happened a third time in April 2015, with a third mystery satellite known as Cosmos 2504.
This satellite, which became known as "Object E" because it was the fifth object cataloged from this launch in addition to the high-level satellite and three communications satellites, has attracted the attention of the US national security community.
However, it is not entirely clear what the purpose of these satellites is or for what purposes Russia is using these rendezvous and proximity operations. Some of these maneuvers are cataloged in detail on the Russian Space website.
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Quoted from Ars Technica, there is no evidence that they were part of weapons tests, experts said. However, the Object E satellite is now causing even more significant concern in low Earth orbit.
In 2019, Cosmos 2491 spilled about 20 pieces of debris. Then, on Monday (13/2/2023), the US military's 18th Space Defense Squadron confirmed that Cosmos 2499 had broken apart in early January.
The split occurred at an altitude of 1169 km and yielded 85 pieces of traceable debris, said the military squadron, which is tasked with tracking all man-made objects in Earth orbit.
Brian Weeden, a space debris expert at the Secure World Foundation who has studied the Object E satellites, said he did not think the debris release events on Cosmos 2491 and Cosmos 2499 were caused by an in-orbit collision. Instead, they seem to be part of a repeating pattern.
"This suggests that perhaps this event was the result of a design flaw in the fuel tank or other system that broke apart after several years in space rather than something like a collision with debris," Weeden said.
In terms of the orbital debris, this does not appear to be a catastrophic event, Weeden said. There aren't many large enough chunks of debris from a small satellite.
However, this debris will live a long time because it started from such a high altitude above the Earth's atmosphere. In comparison, debris generated by China's anti-satellite tests in 2007, when a 750 kg satellite was crushed at an altitude of 865 km, is expected to remain in orbit for many more decades.
So it appears that the shards will likely be with us for the rest of the 21st century before finally falling into Earth's atmosphere. Naturally, experts are increasingly concerned about the presence of debris in Earth's orbit.