TANEGASHIMA, Japan (AP) -- Japan's struggling space program suffered a setback Monday, when its biggest rocket to date gracefully blasted off the launch pad but left half its payload initially lost in space.

Japan's H-2A rocket lifts off from the Pacific Coast at 9:45 p.m. EST on Feb. 3, 2002.

Hours after the black and orange H-2A rocket peeled into a pale blue sky on a billowing column of white smoke, mission controllers were still trying to figure out whether one of two probes had been put in orbit.

The rocket itself fired almost perfectly and successfully deployed the second satellite.

But the initial payload glitch, affecting a 600 million yen ($4.5 million) research module, was another blot on Japan's bid to compete with the United States and Europe in the lucrative satellite launching business.

``If you can't get a satellite in orbit it doesn't count,'' said space analyst Joan Johnson-Freese, of the Asia-Pacific Center for Security Studies. ``It's a blow to the space program, but not an unrecoverable one.''

Japanese space officials tried to stress that point, pledging 11 more launches over the next three years.

``We will study 1,500 points of data from this flight, and make improvements for the future,'' mission spokesman Shinji Nio said, calling Monday's launch a success despite the probe problem.

The space shot of the 8.5 billion yen (dlrs 64 million) rocket was the second and final H-2A test flight from Japan's space center in Tanegashima, a small island more than 980 kilometers (610 miles) southwest of Tokyo.

Japan watched in relief last August when the first H-2A rocket cleared the tower.

NASDA had to scrap an earlier series of rockets, the H-2, when one failed to get its payload in orbit and another had to be exploded by remote control so it wouldn't veer out of control. U.S.-based Hughes Space and Communications International dumped an order for 10 satellite launches with Japan after those snafus.

On Monday, communication with the DASH probe was lost during its scheduled deployment time, halfway across the Pacific Ocean. By late Monday night, scientists at Japan's Institute of Space and Astronautical Science, the probe's creator, determined that it failed to separate from the rocket's second stage.

They said they were still investigating the cause and would try to salvage the probe. But ISAS official Morita Yasuhiro said at an earlier press conference that the DASH mission could be not completed if it stayed attached.

Designed to test re-entry technology for future manned flights, the DASH probe was to circle the earth for three days before plunging to the Sahara Desert.

The second satellite, the 5.7 billion yen (dlrs 43 million) SDS-1, was correctly deployed. It will orbit for about a year testing how commercial components such as microchips, batteries and solar cells perform in outer space.

Among Monday's other successes was the firing of four strap-on booster rockets, used for the first time to give the 57-meter (188-foot) H-2A extra lifting power for its dual cargo.

Successful launches aren't easy, and developing a viable commercial program is even more difficult. Of the 11 H-2A missions tentatively scheduled, all carry Japanese government _ not commercial _ payloads.

The H-2A can lift cargo of up to 4.5 tons, in line with Europe's Ariane rockets and the Delta rockets of the United States. But unlike its competitors who have flexible launch schedules from space centers in Florida and French Guiana, Japan has a limited launch window.

Concessions made to fishermen around Tanegashima restrict rocket launches to 190 days a year. That makes booking flights more difficult, an important issue to commercial customers who often want their satellites launched as soon as possible.

Another question is whether two test launches for the H-2A are enough. The H-2 line had five successful launches in a row before the sixth misfired and the seventh ended in a fireball.

Johson-Freese says Japan may need two more successful back-to-back launches before it wins insurance coverage for commercial missions.