The satellite, along with a smaller test prototype, was launched from the country's space center on a remote southern Japan island atop an H-2A rocket, the workhorse of Japan's space program.

Japanese space agency spokesman Satoki Kurokawa described the liftoff -- which had been postponed three times due to poor weather -- as a success. Television footage showed the rocket racing up through cloudy skies.

The launch of the radar satellite enhances a multibillion dollar (euro), decade-old plan for Japan to have round-the-clock surveillance of the secretive North and other areas Japan wants to peer in on.

But weaknesses in the satellites' capabilities have led to criticism that the program is a waste of money and, with better data available on the commercial market, that Japan will continue to be dependent on Washington for its core intelligence.

Japanese space officials say the satellites provide an important means for the country to independently collect intelligence, and say improvements in the satellites' capabilities are in the works.

The prototype launched Friday, for example, features higher-resolution optics that can be used in the future to improve the quality of the satellites' photographs from orbit.

Japan launched its first pair of spy satellites into orbit in March 2003. The program grew out of concern following North Korea's launch of a ballistic missile over Japan's main island in 1998.

The government's original plan was to put a total of eight intelligence-gathering satellites into orbit through 2006. However, it suffered a major setback in November 2003, when a rocket carrying the second set of spy satellites malfunctioned and was destroyed in mid-flight.

Officials say they are back on course now.

"Our crisis management has improved substantially," said Yasuhiro Itakura of the Cabinet office in charge of the program.

Though Japan's intelligence-gathering satellites are not under military control, Japan's ruling party proposed late last year that the military be allowed to use the country's space program. The proposal still needs to be approved by Parliament.

Since 1969, Japan's space program has been limited by a parliamentary resolution committed to peaceful uses. The new proposal would restrict military use of the program to self-defense, officials say.