You can watch the spacewalk live on the internet.
Josh and Frank are going to the International Space Station. It is expected to last up to seven hours. You can watch it here at Space.com or via the agency. At 6 a.m., coverage starts. The sun rises at 1100GMT.
NASA astronauts Nicole Mann and Koichi Wakata will help install the iROSA in the space station.
There are pictures of the most memorable spacewalks.
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Mann and Wakata will assist the astronauts in and out of their EMUs, maneuver the Canadarm2 robotic arm, as well as monitor the spacewalkers during the excursion.
The groundwork for Saturday's installation was laid during a spacewalk in November. It was the first spacewalk for the two astronauts.
Two of the planned iROSA array have been installed by astronauts. New panels will not replace the current system. The electricity supply will increase by 20% to 30% once all six iROSAs are up and running.
NASA officials said that on Saturday, Cassada will be an extravehicular crew member 1 and will wear a red suit. The EV2 will be wearing a suit.
They are going to install another iROSA during a spacewalk in December. The red-striped suit will be worn by Rubio during that excursion.
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