Astronauts completing four-year power upgrade on International Space Station

Nasa astronauts Mike Hopkins, left, and Victor Glover work outside the International Space Station on Monday February 1 (Nasa/AP)

A pair of Nasa astronauts ventured out on their second spacewalk in under a week to complete a four-year effort to modernise the International Space Station’s power grid.

Over the weekend, flight controllers in Houston used the station’s big robot arm to replace the last pair of old-style batteries with a single better-quality one.