The International Space Station was given a shove by supply ships docked to it over the weekend in order to evade a cloud of high-velocity orbital shrapnel created when a Russian military satellite crashed into an Iridium comsat in 2009.
Aviation Week reports that astronauts and cosmonauts aboard the station fired three different thruster systems late on Friday night. Without this manoeuvre, according to US space tracking, debris generated by the collision above Siberia just over two years ago would have passed within 6.5 miles of the station.
The main shove for the shrapnel dodge came from the European Space Agency's ATV-2 robo supply capsule, docked at the station. The ISS' Russian service module also fired thrusters to provide pitch and yaw control during the burn, and roll control was provided by the thrusters of the Russian Progress supply capsule, also docked at the station.
The collision in 2009 saw Cosmos 2251 – a defunct military communications satellite launched in 1993 – crash into an up-and-running Iridium bird above northern Russia. The Iridium constellation was originally intended to be the world's first global mobile phone network, but as things turned out international GSM roaming beat it to the punch.
Iridium went bankrupt, but was then reborn with US government backing: it remains one of the few solutions offering truly worldwide voice and data (albeit very limited bandwidth) without requiring a cumbersome directional dish. As such it is often used in military and intelligence applications – for instance certain kinds of tracking bugs, communications with submerged submarines etc etc – perhaps offering a clue as to why the US authorities were keen to see it saved.
The 2009 collision was thought to result in only brief, local network outages for the Iridium system and full coverage was restored swiftly. The resulting wreckage pushed up overall space debris levels in near-Earth space by around 3 per cent. Initially the debris cloud was not dangerous to the ISS, but as time has gone by some of the fragments have descended to the same orbital level as the station.
Following the satellite crash, conspiracy theories circulated widely to the effect that Russia might have taken the Iridium satellite out on purpose – perhaps in order to prevent a particular satphone call/tracking bug report/submarine "page" etc from getting through.
Regardless of such considerations, debris is a growing threat to all space operations. At the moment most countries rely on the US military Space Surveillance Network to monitor the situation, but the ESA has aspirations towards a system of its own in future. ®