On December 21, 2015 American astronauts Scott Kelly and Timothy Kopra performed the spacewalk. They freed up a stalled robot arm-carrying transporter so it could be moved to a nearby anchor point and locked down, clearing the way for a Russian Progress supply spacecraft to dock on December 23. The EVA lasted 3 hours and 16 minutes. This was the 191st spacewalk since station assembly began in 1998, the third for Kelly and the second for Kopra.