Two astronauts completed the first space walk of shuttle Endeavour's final mission Friday to install antennas and routing cables outside of the International Space Station.

The nearly 6 1/2 hour walk was cut short after mission controllers noticed Gregory Chamitoff's carbon dioxide sensor wasn't working.

This was the first of four space walks for the Endeavour crew.

Mark Kelly, the husband of Ariz. Rep. Gabrielle Giffords, is leading the final Endeavour mission.

Giffords has been recovering for months from an assassination attempt against her in Tucson, Ariz., that killed six people and wound 12 others.

A helmet to protect her injured scull was removed this week. Doctors, who are now calling her "gorgeous Gabby," say she's awake, communicating and doing bedside therapy.