Japan is poised to have four working Information Gathering Satellite (IGS) spacecraft on orbit following the successful Sept. 23 launch of IGS Optical 4. But the constellation of reconnaissance satellites is still many months from delivering its intended operational capability.

The satellite, which promises the same half-meter resolution imagery as the IGS Optical 3 satellite launched in November 2009, lifted off from Tanegashima Space Center aboard an H-2A rocket. Originally scheduled for August, the launch was delayed twice — once because of a glitch with the rocket’s range safety system and a second time because of a typhoon.

Designed to enable reasonably close coverage of North Korea and other parts of East Asia, the IGS constellation is supposed to consist of two optical and two radar satellites. A series of launch mishaps and on-orbit failures, however, has left Japan with three working optical satellites and no working radar satellites.

Japan plans to launch an IGS radar satellite within the next six months, according to an official with Japan’s Cabinet Satellite Intelligence Center. A second radar satellite is expected to launch before the end of March 2013, the official said. A third-generation optical satellite is in the plans for a late 2013 or early 2014 launch.

“We are continually investing in improving both the radar and optical satellites, but beyond the improved optical satellite we don’t have any fixed development schedule yet,” the official said.

IGS satellites are built by Mitsubishi Electric Corp. in its Kamakura factory near Tokyo.