With the Earth's horizon in the background, spacewalker Dan Tani performs a routine glove check in this view provided by his helmet camera and shown on NASA TV December 18, 2007. Tani and spacewalker Peggy Whitson (not pictured), who are on the International Space Station, will check for damage to a critical part of the outpost's power system during the planned 6.5-hour spacewalk. [Agencies]