Soviet cosmonauts Vladimir Titov and Musa Manarov took a spacewalk Thursday and replaced a telescope component on the Mir orbital space station, the Tass news agency said. The cosmonauts, seeking to break the space endurance record, replaced a detector unit on an X-ray telescope of an astrophysics module attached to the outside of the space platform. Titov and Manarov, who blasted off last Dec. 21, hope to beat cosmonaut Yuri Romanenko's record of 326 days in space, which was set last year.