
A NASA handout picture shows Expedition 24 Flight Engineer Doug Wheelock (R) and Tracy Caldwell Dyson (L) working outside the International Space Station (ISS) during the first of two spacewalks to replace a failed ammonia pump module on 07 August 2010. Two astronauts left the ISS to perform a complicated spacewalk to fix a broken cooling system that last weekend prompted the shutdown of some systems onboard the orbiting spacecraft. EPA/NASA TV - HANDOUT QUALITY FROM SOURCE EDITORIAL USE ONLY/NO SALES

A NASA handout picture shows Expedition 24 Flight Engineer Doug Wheelock working outside the International Space Station (ISS) during the first of two spacewalks to replace a failed ammonia pump module on 07 August 2010. Two astronauts left the ISS to perform a complicated spacewalk to fix a broken cooling system that last weekend prompted the shutdown of some systems onboard the orbiting spacecraft. EPA/NASA TV - HANDOUT QUALITY FROM SOURCE EDITORIAL USE ONLY/NO SALES