NASA astronauts Jessica Meir and Christina Koch are taking their third spacewalk outside the International Space Station today (Jan. 20) to replace the orbiting laboratories aging batteries and you can catch the epic action live online.

The spacewalk began at 6:35 a.m. EST (1335 GMT) today, marking the third time an all-woman team has worked together outside the station. You can watch the spacewalk live here and on Space.com's homepage, courtesy of NASA TV.

Meir and Koch are wrapping up work that began in October 2019, to upgrade the batteries that store power generated by the space station's solar array. Their first spacewalk (which was the first all-woman spacewalk ever) took place Oct. 18. A second spacewalk successfully wrapped up Jan. 15.

Related: The amazing spacewalks of Expedition 61 in photos

Astronauts use power in space for everything from lighting rooms to conducting experiments. The upgraded batteries are lithium-ion batteries, which are expected to last longer and to generate more power than the previous generation nickel-hydrogen batteries that were installed several years ago.

If Koch and Meir finish the last battery spacewalk as expected, there's another spacewalk by other astronauts coming shortly. NASA astronaut Andrew Morgan and Italian ISS commander Luca Parmitano are expected to exit the ISS Saturday (Jan. 25), but for a different task.

Parmitano and Morgan spent much of the end of 2019 working on the Alpha Magnetic Spectrometer (AMS), which is an aging dark matter experiment on the ISS. The astronauts, in concert with teams on the ground, are doing a complex repair that NASA says is the toughest work the agency has done in space since the last Hubble Space Telescope upgrade in 2009.

The duo completed three of four planned AMS spacewalks in 2019. In December, NASA warned that the battery spacewalks (which are more urgent than the AMS spacewalks) and a busy schedule of visiting space vehicles could delay the last AMS spacewalk.

As of this week, however, NASA is projecting all spacewalks will be finished before half of the six-person Expedition 61 crew returns to Earth in a Russian Soyuz spacecraft. Three astronauts will remain in space as NASA works out the sequence of future missions, which is under discussion as final tests are being run for American commercial crew vehicles to fly astronauts. (Currently, all astronauts fly to the ISS using the Soyuz, but NASA is seeking to shift most of their astronauts to commercial crew vehicles.)

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Spacewalking astronauts are upgrading the space station today. Here's how to watch it live. - Space.com