Ammonia radiators on Station

NASA Astronaut Nicole Stott, Expedition 20 flight engineer, during a six-hour spacewalk. Nicole and NASA astronaut John Olivas removed an empty ammonia tank from the Station and retrieved the European Technology Exposure Facility and Materials International Space Station Experiment from outside ESA’s Columbus laboratory module and installed them in Space Shuttle Discovery for return to Earth.

The white ammonia-cooled radiators can be seen in the background.