Having been idle for more than a year, one of the satellites went hundreds of metres off its orbit last month to within 1,200 metres of a piece of a Chinese weather satellite that China smashed in a 2007 anti-satellite rocket test.
The manoeuvre, which is pretty impressive for such a small spacecraft, is also rather close by orbital standards.
No one quite knows what the satellites are for, but some experts say they could be "technology-demonstrators" or even "precursors to orbital weapons", according to The Daily Beast.
Code named Kosmos-2491, Kosmos-2499 and Kosmos-2504, the three satellites manoeuvred several times in the last three years to within a few dozen feet of their old booster shells.
This means that they could be inspection satellites that can scan and match the orbit of other spacecraft, possibly even interact with it physically for repairs, modifications or to dismantle it.
It's also possible that these satellites could be used for warfare. "You can probably equip them with lasers, maybe put some explosives on them," Anatoly Zak, an independent expert on Russian spacecraft, told The Beast in 2015.
"If [one] comes very close to some military satellite, it probably can do some harm."
In 2012, US intelligence completed a report analysing "the growing vulnerability of US satellites that provide secure military communications, warn about enemy missile launches, and provide precise targeting coordinates", anonymous sources told Reuters.
The report raised many concerns about China's ability to disrupt satellites in higher orbits, possibly putting sensitive US spacecraft at risk, the sources told Reuters.
But Russian space agency chief Oleg Ostapenko claimed in 2014 that the satellites were for peaceful purposes.
Read the full article from The Daily Beast here.
This article was originally published by Business Insider.