A radar spy satellite impervious to darkness and a second-generation craft with optical cameras were successfully launched into space Saturday to begin top secret reconnaissance missions for the Japanese government.

The radar craft is the second such satellite to be orbited in Japan's spy satellite program. Two other satellites with optical instruments were launched in 2003 and last year. The third optical spacecraft launched Saturday reportedly features upgraded imaging capabilities, according to Japanese media agencies.

Liftoff of the two-stage H-2A rocket was at 0441 GMT (11:41 p.m. EST Friday) from the Yoshinobu launch complex at the Tanegashima space center. The launcher was fitted with a pair of 50-foot-long solid rocket boosters and four other smaller solid-fueled motors.

The rocket flew south from Tanegashima before deploying its classified payloads into the planned polar orbit about 300 miles above the Pacific Ocean. Power-producing solar panels aboard the two satellites were to be deployed several hours later.

The launch was postponed for more than a week due to poor weather conditions, which included low clouds, gusty winds and consistent precipitation. The gray clouds parted and winds diminished to finally permit launch Saturday afternoon, Japan time.

Next for the secretive radar satellite will be the activation of its synthetic aperture radar equipment. The radar system sends radio signals toward Earth, and those beams are reflected back to receivers aboard the spacecraft.

Because the radar does not require ideal ground conditions, the instrument can see regions shrouded in clouds and darkness. Experts believe the craft can see objects between five and ten feet wide.

Less is known about the experimental optical spacecraft delivered into orbit Thursday. It could signal the next phase of Japan's space-based reconnaissance program.

Cameras on the fleet's earlier optical satellites likely have a resolution of around three feet, which is comparable to most commercial remote sensing satellites currently in use.

The newest optical craft may include upgrades in its instruments and cameras that could improve image resolution, but officials remain silent on technical details.

The launch was the final step in the secretive fleet's full recovery from the loss of a pair of spy satellites during a launch failure in November 2003.

Program managers split the second pair of optical and radar craft into two launches in the wake of the failed 2003 mission, and an optical satellite was launched alone in September. Saturday's launch also marked the return to dual launches for the program.

With a full constellation of reconnaissance satellites, Japan now has the ability to gather imagery of any place in the world every day. It is believed radar and optical spacecraft orbit in tandem in Sun-synchronous orbits.

The satellites are believed to be designed to operate in pairs in two orbital planes - one flying over during the morning and the other in the afternoon. The spacecraft launched Saturday were likely placed into the afternoon orbital plane.

Using two Sun-synchronous orbits "effectively double(s) the number of imaging opportunities each day," veteran satellite-watcher Ted Molczan said in a 2003 interview.

The spacecraft are operated by the Japanese government, which established the spy satellite program after North Korea fired a ballistic missile over Japanese territory in 1998. Japanese intelligence analysts previously relied on U.S. government reconnaissance imagery and commercial observation satellites.

The satellites are publicly called Information Gathering Satellites by Japan's government, and officials have long touted the program's ability to provide aid in natural disasters and environmental monitoring. Critics say the program violates a 1969 Japanese law that banned military use of space assets.

Upcoming launches for Japan include the nation's first lunar probe, which is set for blastoff in July. An advanced broadband communications test satellite should launch aboard another H-2A rocket late this year.