A Nasa power outage disrupted communication between Mission Control and the International Space Station on Tuesday.
Mission Control could not send commands to the station or talk to the seven astronauts in orbit.
The power outage hit as upgrade work was under way in the building at Houston’s Johnson Space Centre.
Space station programme manager Joel Montalbano said neither the astronauts nor the station were in any danger and that back-up 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 is the first time Nasa has had to fire up these back-up systems to take control, according to Mr 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 centre 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.
