The USS Greeneville's sonar detected the Ehime Maru an hour before the submarine struck and sank the Japanese trawler, a federal investigator has said. But a crew member plotting sonar readings was interrupted by the presence of civilians in his work space.
Mr John Hammerschmidt, a member of the National Transportation Safety Board, told reporters in Hawaii the submarine's sonar detected what US Navy analysis later determined to be the Ehime Maru more than an hour before the collision on February 9th.
The Greenville's sonar picked up the Japanese vessel at 12.32 p.m. and held it on a track designated Sierra 13, he said.
The submarine's fire control man of the watch told investigators he was plotting sonar tracks with pencil and paper but was unable to continue less than an hour before the collision because of the presence of civilians in the work space, Mr Hammerschmidt said.
"He told us in interview that he was not able to continue his plotting because of the civilians in the area, and he also said that he did not ask anyone to move."
Mr Hammerschmidt said investigators still do not know how important that lapse was to the collision, which sank the Ehime Maru in minutes and left nine of its 33 crew members missing and presumed dead.
"We thought it was an anomaly we thought should be reported," he said.
The navy refused to comment on either the NTSB findings or a report by the Washington Times that cited an unnamed navy source as saying the Greeneville's sonar had picked up sound from a vessel but concluded from its noise signature that it was a small boat at a safe distance.
The Times said a fire control technician also detected the Ehime Maru's sonar signature at 4,000 yards, or two nautical miles, from the Greeneville but did not report it to the ship's commander.
The Japanese Prime Minister, Mr Yoshiro Mori, said yesterday he would delay a visit to Washington to meet President Bush, losing a chance to repair relations damaged by the sinking of the trawler.