Japan’s fleet of reconnaissance satellites has been reduced to two operational satellites following the malfunction of the fleet’s remaining radar satellite only halfway through its nominal five-year mission, according to an official at the Cabinet Satellite Intelligence Center.

The official, who asked not to be named, said that the IGS-Radar-2 satellite, which was launched in February 2007, stopped sending radar data on Aug. 23 due to an undisclosed problem with the satellite’s electrical system.

The breakdown echoes the premature malfunction of the satellite’s predecessor radar satellite, which was of the same design and also stopped operating due to an undisclosed electrical systems malfunction. That failure occurred in March 2007, four years into the satellite’s five-year mission. Both satellites were built by Mitsubishi Electric Co. of Tokyo.

The official declined to state the suspected nature of the failure and any connection between the most recent and the prior malfunctions. “We can’t say whether or not it was the battery or other systems officially, or whether the two incidents are connected in any way, as it’s still under investigation,” the official told Space News Aug. 31. However, the loss does leave a gaping hole in the IGS’s coverage.

Japan’s reconnaissance satellite program is designed to function as a fleet of two radar and two optical satellites to provide coverage of North Korea and the rest of East Asia.

Japan’s first-generation radar satellites are able to peer through clouds to resolve objects on the ground as small as 1 to 3 meters across. Its optical satellites provide 1-meter resolution imagery.

The latest failure means that the fleet will be without radar coverage until the launch of the next radar reconnaissance satellite in fiscal 2011, the official said.