Video: Soyuz MS-01 leaves the space station for landing

Space station commander Chris Cassidy and Robert Behnken plan to float outside Friday for the first of up to four spacewalks needed to complete the replacement of aging batteries in the lab’s solar power system. NASA managers hope to get the work done in time for Behnken and crewmate Douglas Hurley to return to Earth aboard their Crew Dragon capsule by around Aug. 2, officials said Wednesday.

Launch of a Russian Soyuz spacecraft Friday carrying three fresh crew members to the International Space Station will boost the lab’s crew back to six and, most important from NASA’s perspective, dramatically boost research with four crew members — three NASA astronauts and a veteran European flier — available to operate experiments in the American segment of the laboratory.

The sixth commercial cargo delivery by Orbital ATK’s Cygnus spacecraft, and the first using an Antares rocket since a launch failure in 2014, will carry more than 5,000 pounds of equipment to the International Space Station.