Signals from a transmitter attached to a rocket booster -- believed to have been the cause of the failure of the launch in November of an H-IIA rocket carrying spy satellites -- have been detected in the Pacific off the Philippines, Japan's space agency said Thursday.
But the Japan Aerospace Exploration Agency is still unable to pin down the exact location of the booster.
Mechanical problems in the passive sonar being used have forced investigators to return to Japan and the search will be resumed next week at the earliest.
The sound waves were detected on Jan. 1 in an area measuring 10 km by 5 km and between 5 km and 6 km deep, where the agency had earlier assumed the booster had fallen, a JAXA official said.
But the sonar broke down as they were narrowing the area down to a 3-km by 3-km range, the official said.
The sound waves were sent by a transmitter attached to the booster. It generally emits signals for about three months.
The agency suspects the booster failed to separate from the H-IIA rocket after a nozzle that emits fuel gas was damaged. It is not known how the component may have been damaged.
If the booster is located, an underwater search vessel equipped with cameras will take pictures of it and the agency will then decide whether it should be recovered, the official said.
The agency launched the H-IIA on Nov. 29 from the Tanegashima Space Center in Kagoshima Prefecture to send two satellites into space to monitor North Korea.
But the mission failed when the launch vehicle was deliberately destroyed by the ground crew shortly after liftoff because one of the two boosters failed to disengage after burning off its fuel.