Space object 2014-28E was launched from the Plesetsk Cosmodrome in northern Russia on 23 May alongside three communications satellites. The US Air Force Space Command is believed to be monitoring it closely.
The three satellites that launched alongside it – Kosmos 2496, 2497 and 2498 – are thought to be for military communications, says David Todd, an analyst with space-flight data provider Seradata of Welford, UK. "The fourth spacecraft, Kosmos 2499, is making regular changes to its orbit, including making a visit on 28 October to the Briz-M rocket stage that launched it," he says.
A satellite-killing spacecraft – also known as an anti-satellite weapon, or ASAT – needs to be able to carry out such manoeuvres. Such a spacecraft could visit and cripple spy satellites, say, by placing a small disabling explosive charge on them, or using a robot arm to disable their solar panels.
Severing the solar arrays makes more sense, says Todd, because it creates less space debris, which can harm all space users. "Disabling the arrays kills the power supply, and once you lose that you are dead, as we saw with the Philae comet lander this week."
Space debris from ASATs is already a threat: in 2007, China tested used a ground-to-air missile to destroy a defunct weather satellite. The shot caused international opprobrium and the resulting shower of 3000 pieces of debris is still troubling spacecraft. The International Space Station needs to change orbit regularly to avoid it.
Very cold war
In the 1960s, the Soviet Union had an active ASAT programme, but this was abandoned as the cold war came to an end. However, in 2010, with relations between the West and Russia deteriorating, Russian space commander Oleg Ostapenko revealed that such weapons were being studied again.
News of Kosmos 2499 comes as Russian relations with the West hit a new low, after president Vladimir Putin left the G20 meeting in Brisbane, Australia, early after enduring days of criticism over Russia's intervention in Ukraine.
But there may be a more prosaic explanation for Kosmos 2499. Other nations, including the US, have spacecraft to carry out maintenance on satellites. Kosmos 2499 might just be doing the same, Todd says.
And the US air force X-37B space plane, which spends many months on mystery missions in orbit at a time, is also capable of precision movements – and may have the ability to inspect, if not destroy, satellites.