Gerst walks on ISS wild side

German astronaut Alexander Gerst on Tuesday faced his toughest test so far during four months aboard the International Space Station (ISS), completing a spacewalk lasting more than six hours with his US crewmate Wiseman.

Gerst quoted a Lou Reed song on Twitter ahead of the challenging mission, inviting Wiseman to join him for a "walk on the wild side."

He also offered "greetings to all German space travel enthusiasts" at the end of the mission. Weisman decided to opt for muted understatement on his Twitter account, describing the view afforded by the mission as "reasonably INSANE."

Gerst was following in the footsteps - not that any were actually laid - of German astronauts Thomas Reiter and Hans Schlegel, who completed spacewalks at the ISS in 2006 and 2008, respectively.

Gerst and Wiseman completed the NASA-run "EVA" (extra-vehicular activity) in 193 minutes, performing clean-up, replacement and installation tasks on the exterior of the station. Originally slated for August, EVA-27 was delayed due to concerns with battery units in the "Extravehicular Mobility Unit" (EMA). The latest cargo runs to the ISS - by a private-sector US-built CRS-4 Dragon capsule and most recently a Russian Soyuz capsule - delivered new longer-life batteries for the unit.

Neither astronaut had ever conducted a spacewalk before. Crewmate Barry "Butch" Wilmore of NASA, who arrived at the station late in September, operated the robotic arm and guided the duo as they worked. The three Russian cosmonauts completing the six-person ISS crew helped monitor the mission.

One task completed on Tuesday was the permanent relocation of a failed Pump Module that had been placed in temporary storage outside the station last December after two successful spacewalks to fit a replacement part. That complex mission was expected to require three EVAs - but once the ISS crew finished the crucial tasks in just two, they decided to postpone moving the faulty pump to its permanent point of storage. Only one valve on the Pump Module has been identified as faulty, meaning that it could be repaired and re-used as a back-up system in future.

The astronauts also installed Mobile Transporter Relay Assembly (MTRA), which serves as a secondary source of power for a system - the Mobile Transporter - used to shift supplies on rails along the station's backbone.

European Space Agency astronaut Gerst, or "Astro Alex," arrived at the ISS in May this year, and is scheduled to depart in November. During his time in space, he has posted numerous pictures and updates to his Twitter account, both about his mission and some of the sights he can take in from orbit.

msh/rc (AFP, dpa)