Update for 4 pm, Dec. 21: NASA astronauts Josh Cassada and Frank Rubio will now spacewalk outside the International Space Station on Thursday, Dec. 22, after a one-day delay due to a space debris encounter on Dec. 21 that forced the station to maneuver away from a piece of an old Russian Fregat rocket upper stage. The spacewalk will begin at 8:30 a.m. EST (1330 GMT), with NASA TV coverage beginning at 7 am ET (1200 GMT).
Two NASA astronauts will conduct a spacewalk early Thursday (Dec. 22) to install new solar arrays on the International Space Station (ISS), and you can watch it live.
Josh Cassada and Frank Rubio are scheduled to venture outside the orbiting lab at 8:30 a.m. EST (1330 GMT) Wednesday on a spacewalk expected to last about seven hours. You can follow the action live here at Space.com, courtesy of NASA, or directly via the agency (opens in new tab), beginning at 7 a.m. EST (1200 GMT).
Cassada and Rubio will install a new ISS Roll-Out Solar Array (iROSA), the fourth of six such structures pegged for the orbiting lab's exterior. The iROSAs will augment the station's current solar panel system; when all six are up and running, the orbiting lab's power supply will increase by 20% to 30%, NASA officials have said.
NASA astronaut Nicole Mann and Japan's Koichi Wakata will aid Cassada and Rubio on Wednesday from inside the orbiting lab.
Mann and Wakata "will be at the robotics workstation commanding Canadarm2 and assisting the spacewalking duo during the fine-tuned installation job," NASA officials wrote in an update on Tuesday (opens in new tab) (Dec. 20).
Thursday morning's spacewalk was originally scheduled to take place on Monday (Dec. 19). But NASA pushed it back two days, because the agency wanted to use the cameras on the end of the robotic, 57.7-foot-long (17.6 meters) Canadarm2 to inspect a leaky Russian Soyuz capsule that's docked with the ISS. It was delayed another day after the late discovery of a potential close call by a piece of space debris from an old Russian Fregat upper stage booster on Dec. 21. That debris concern prompted ISS managers to postpone the spacewalk and move the station clear of the debris.
That Soyuz, known as MS-22, suffered a coolant leak on Dec. 14, as two Russian cosmonauts were prepping for a spacewalk of their own (which ended up being canceled).
During the Sunday (Dec. 18) Soyuz inspection, Canadarm2's cameras spotted a small hole near the suspected leak site. Russian space officials are studying the hole as they try to determine the flightworthiness of the Soyuz, which is supposed to return Rubio and two cosmonauts to Earth in March. If MS-22 can't fly safely, Russia will launch another Soyuz to the ISS to take the trio home.
Mike Wall is the author of "Out There (opens in new tab)" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall (opens in new tab). Follow us @Spacedotcom (opens in new tab), Facebook (opens in new tab) and Instagram (opens in new tab).