A planned spacewalk outside the International Space Station has been postponed due to a “medical concern” with one of the crew members aboard the orbital complex, NASA announced Wednesday.

The excursion was set to begin Thursday morning. Astronauts Mike Fincke and Zena Cardman planned to head outside the space station for six-and-a-half hours to prepare for the installation of new roll-out solar arrays set to arrive later this year. The arrival of the new solar arrays will be the final major upgrade to the lab’s electrical system before the space station’s decommissioning in 2030.

Privacy paramount

NASA said the crew member’s medical concern arose Wednesday afternoon, and officials will reschedule the spacewalk.

“Due to medical privacy, it is not appropriate for NASA to share more details about the crew member,” the agency said in a statement. “The situation is stable. NASA will share additional details, including a new date for the upcoming spacewalk, later.”

This was supposed to be the first of two spacewalks this month. On a second excursion next week, astronauts were expected to complete a series of maintenance tasks outside the station.