Two Russian cosmonauts and a US astronaut touched down safely in central Kazakhstan today, following a 173-day mission aboard the International Space Station. <br/><br/><br/>Of the trio that blasted off towards the ISS together in October, only Ryzhikov completed a first mission. Former Gulf War helicopter pilot Kimbrough spent close to 16 days on the US space shuttle Endeavour in 2008, while Borisenko was on his second ISS mission following a 164-day stint in 2011.