A NASA power outage disrupted communication between Mission Control and the International Space Station on Tuesday.

Mission Control couldn’t send commands to the station and talk with the seven astronauts in orbit. The power outage hit as upgrade work was underway in the building at Houston’s Johnson Space Center.

Space station program manager Joel Montalbano said neither the astronauts nor station were ever in any danger and that backup control systems took over within 90 minutes. The crew was notified of the problem through Russian communication systems, within 20 minutes of the outage.

It’s the first time NASA has had to fire up these backup systems to take control, according to Montalbano. He said NASA hoped to resolve the issue and be back to normal operations by the end of the day.

NASA maintains a backup control center miles from Houston in the event a hurricane or other disaster requiring evacuations. But in Tuesday’s case, the flight controllers stayed at Mission Control since the lights and air-conditioning still worked.

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The Associated Press contributed to this article.