PERTH, Australia -- A ship searching for the missing Malaysian jet has detected two more signals that are consistent with a plane's black boxes, the Australian official in charge of the search said early today.
Angus Houston, the head of a joint agency coordinating the search for the missing plane in the southern Indian Ocean, said that the Australian navy's Ocean Shield picked up the two signals in a sweep on Tuesday.
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The Ocean Shield first detected the sounds late Saturday and early Sunday before losing them, but managed to find them again on Tuesday, Houston said. The ship is equipped with a U.S. Navy towed pinger locator that is designed to pick up signals from a plane's black boxes.
"Hopefully in a matter of days, we will be able to find something on the bottom that might confirm that this is the last resting place of MH370," Houston said at a news conference in Perth, the starting point for the search in the southern Indian Ocean.
Finding the sound again is crucial to narrowing the search area so a small submarine can be deployed to chart a potential debris field on the seafloor. If the autonomous sub was used now with the sparse data collected so far, covering all the potential places from which the pings might have come would take many days.
"The better Ocean Shield can define the area, the easier it will be for the autonomous underwater vehicle to subsequently search for aircraft wreckage," Houston said.
Malaysia Airlines Flight 370 carrying 239 people on board went missing March 8 on a trip from Kuala Lumpur, setting off one of aviation's biggest mysteries. The search has shifted from waters off of Vietnam, to the Strait of Malacca and then finally to waters in the southern Indian Ocean as data from radar and satellites was further analyzed.
The locator beacons on the black boxes have a battery life of only about a month -- and Tuesday marked exactly one month since the plane vanished. Once the beacons blink off, locating the black boxes in such deep water would be an immensely difficult, if not impossible, task. "This is an herculean task -- it's over a very, very wide area, the water is extremely deep," Johnston said. "We have at least several days of intense action ahead of us."
Houston also warned of past false leads -- such as ships detecting their own signals. Because of that, other ships are being kept away, so as not to add unwanted noise.
"We're very hopeful we will find further evidence that will confirm the aircraft is in that location," Houston said.
"There's still a little bit of doubt there, but I'm a lot more optimistic than I was one week ago."
Such optimism was overshadowed by anguish at a hotel in Beijing where around 300 relatives of the flight's passengers -- most of whom were Chinese -- wait for information about the plane's fate.
One family lit candles on a heart-shaped cake to mark what would have been the 21st birthday of passenger Feng Dong, who had been working in construction in Singapore for the past year and was flying home to China via Kuala Lumpur. Feng's mother wept as she blew out the candles.
A family member of another passenger said staying together allowed the relatives to support one another through the ordeal. "If we go back to our homes now it will be extremely painful," said Steve Wang. "We have to face a bigger pain of facing uncertainty, the unknown future. This is the most difficult to cope with."
Investigators have not found any explanation yet for why the plane lost communications and veered far off its Beijing-bound course, so the black boxes containing the flight data and cockpit voice recorders are key to learning what went wrong.
"Everyone's anxious about the life of the batteries on the black box flight recorders," said Truss, who is acting prime minister while Tony Abbott is overseas. "Sometimes they go on for many, many weeks longer than they're mandated to operate for -- we hope that'll be the case in this instance. But clearly there is an aura of urgency about the investigation."
The first sound picked up by the equipment on board the Ocean Shield lasted two hours and 20 minutes before it was lost, Houston said. The ship then turned around and picked up a signal again -- this time recording two distinct "pinger returns" that lasted 13 minutes. That would be consistent with transmissions from both the flight data recorder and the cockpit voice recorder.
The black boxes normally emit a frequency of 37.5 kilohertz, and the signals picked up by the Ocean Shield were both 33.3 kilohertz, U.S. Navy Capt. Mark Matthews said.
Houston said the frequency heard was considered "quite credible" by the manufacturer, and noted that the frequency from the Air France jet that crashed several years ago was 34 kilohertz. The age of the batteries and the water pressure in the deep ocean can affect the transmission level, he said.
The Ocean Shield is dragging a pinger locator at a depth of 1.9 miles. It is designed to detect signals at a range of 1.12 miles, meaning it would need to be almost on top of the recorders to detect them if they were on the ocean floor, which is about 2.8 miles deep.