Astronauts onboard the U.S. space shuttle Atlantis have embarked on their first of three spacewalks.
The U.S. space agency NASA says astronauts Garrett Reisman and Steve Bowen are venturing outside the International Space Station to install a second antenna.
They will also add a spare parts platform, as well as loosen battery bolts in preparations for later spacewalks.
Monday's spacewalk is expected to last six-and-a-half hours.
Atlantis, which is on its final mission before the shuttle is retired, arrived at the orbiting space station Sunday.
The six shuttle astronauts are spending a week working at the space station. The crew also delivered batteries and parts for a Russian-made laboratory that will be used to conduct scientific experiments.
NASA has used Atlantis for 25 years, and plans only two more shuttle missions after this one, using other shuttles.
After the space agency retires its shuttle fleet later this year, partners in the International Space Station will use Russian and private rockets to send astronauts and supplies to the center, which is orbiting the Earth.