The Mission Control team at NASA's Johnson Space Center in Houston confirmed Friday night that a backup computer on the exterior of the International Space Station (ISS) called a Multiplexer-Demultiplexer (MDM) is not responding to commands. The station's MDM computers control some systems associated with robotics aboard the space station.

The primary MDM operating aboard the space station is functioning normally and there is no immediate impact to space station operations. The computer outage does not pose a risk to the six crew members aboard the space station. ISS teams are assessing next steps to attempt to bring the computer back online or replace it. Replacing the backup MDM, if needed, would require a spacewalk.

The backup MDM would provide redundancy for robotic systems that will be needed to attach the SpaceX Dragon spacecraft currently scheduled to launch on Monday and rendezvous with the ISS on Wednesday. NASA is continuing to work toward a Monday launch of the SpaceX cargo resupply mission pending further evaluations by the ISS Program.

The six-member Expedition 39 crew was off-duty Friday in recognition of Cosmonautics Day. Russian President Vladimir Putin called the International Space Station to congratulate the crew the day before Cosmonautics Day, April 12, the anniversary of the historic first human spaceflight by Yuri Gagarin.

The station is set for an orbital reboost Saturday morning when the ISS Progress 53 resupply craft, docked to the Zvezda service module, will fire its thrusters for 13 minutes, 32 seconds. This will put the orbital lab at the correct altitude for a crew swap in May.

Expedition 38/39 crew members Mikhail Tyurin, Koichi Wakata and Rick Mastracchio will return to Earth May 14 inside the Soyuz TMA-11M spacecraft. They will be replaced May 29 when the Expedition 40/41 crew of Maxim Suraev, Reid Wiseman and Alexander Gerst arrive inside the Soyuz TMA-13M spacecraft.

Another cargo ship is set for a launch to the space station on Monday at 4:48 p.m. EDT. The Dragon commercial cargo craft will liftoff atop a Falcon 9 rocket on the SpaceX-3 mission from Cape Canaveral Air Force Station, Fla.

The third Dragon capsule to visit the station will deliver about 5,000 pounds of gear and return 3,500 pounds of cargo, including science results for analysis, to Earth. When Dragon is captured and berthed to the Harmony node, there will be five space vehicles parked to the international space laboratory.