Two Chinese satellites seem to have had a close encounter – and may have even touched – 600 kilometres above Earth, a new analysis shows. The unannounced rendezvous – a first for China – could be a test of technology needed to build a space station, but it also shows the country has the capability to approach and potentially interfere with other satellites.

The rendezvous, first reported by Russian media, occurred between two Chinese “Shi Jian” (“Practice”) spacecraft, SJ-06F and SJ-12, that are officially designated as science satellites. A new analysis by Brian Weeden, a technical consultant at the Secure World Foundation, which promotes the peaceful use of space, confirms that the probes seem to have come close to each other.

According to tracking data collected by the US military, SJ-12 has performed multiple manoeuvres since its launch in June, slowly shifting its orbit to match that of SJ-06F. The satellites may even have made contact, Weeden says. Preliminary data suggests that SJ-06F may have been nudged slightly on 19 August, and natural causes – such as the drag of Earth’s atmosphere – do not seem to be responsible.

In the past, US satellites have been commanded to approach and dock with other spacecraft. But “to the best of my knowledge, [this is] the first time anyone but the US has done a close rendezvous outside of space station work,” Weeden told New Scientist. “It is an important milestone in the development of Chinese technology and their ability to operate in space.”


Dual-use technology

The ability to rendezvous in orbit could be used to help clear out space junk or inspect or fix satellites. But the capability is considered dual-use, in that the technology could also be used to damage or interfere with satellites from other countries.

“This set of skills serves a whole lot of purposes,” says Dean Cheng, a Chinese policy expert with the Heritage Foundation, a think tank in Washington DC.

The most immediate application, Cheng says, may be testing sensors and control systems to help pave the way for docking procedures to be used with China’s first space station module, Tiangong-1, which is set to launch in 2011.

“This sort of thing may very well be consistent with wanting to test drive the hardware and software before you test it on your space laboratory,” Cheng says. “You’d be doing it on a smaller, cheaper, less prestige-oriented item so that if something went wrong, it wouldn’t necessarily be politically disastrous.”

Weeden agrees. He says it is likely that the technology is not intended for military purposes, since it would be easier to interfere with satellites using other methods, such as by blinding them with ground-based lasers.

But he adds that the test highlights the need for transparency to prevent misunderstanding. “If the purpose was benign, then why have they been so quiet about this?” Weeden says. “If these sorts of activities are done secretly, if they’re done without a level of transparency, then that can create misperception.”

Two satellite shoot-downs in recent years have fuelled fears of space-based battles. In January 2007, China destroyed a defunct satellite with a ballistic missile, and in February 2008, the US did likewise.