After picking up signals from what investigators hope is missing Malaysian Airlines Flight 370's black box over the weekend, searchers have again detected underwater pings, raising hopes that they are getting closer to finding the plane. 

Houston. REUTERS/Richard Polden

Australian Angus Houston, in charge of coordinating the search, said on Wednesday that the two new signals, one picked up for five minutes and 32 seconds and the other for about seven minutes, are consistent with the type of data sent out by black boxes. "I'm now optimistic that we will find the aircraft, or what is left of the aircraft, in the not-too-distant future — but we haven't found it yet, because this is a very challenging business," he said, adding "I think that we're looking in the right area, but I'm not prepared to say — to confirm — anything until such time as somebody lays eyes on the wreckage." 

The signals have made it possible for officials to narrow down the search area, but they need to do so even more before sending out submarines to search the ocean floor for possible debris. The Associated Press explains

Picking up the sound again is crucial to narrowing the search area so a small, unmanned submarine can be deployed to create a sonar map of a potential debris field on the seafloor. It takes the sub, dubbed "Bluefin 21," six times longer to cover the same area than it does the towed pinger, which is pulled behind the boat at a depth of 9,800 feet. U.S. Navy Capt. Mark Matthews said the detections indicate the device emitting the pings is somewhere within about a 12 mile radius. Still, he said, that equates to a 500 square mile chunk of the ocean floor, which would take the sub about six weeks to two months to canvass. 

Officials have been relying on black box detecting technology to determine the parameters of a contained search area before sending out submarines. They have also deployed sonar buoys: 

The new pings come 31 days after the plane lost contact with ground control. As has been repeatedly noted, the plane's black box is only expected to emit signals for 30 days following a crash before it loses battery power, so fears are high that the signals could stop being sent out at any moment. Sunday's signals lasted much longer than Tuesdays, one of which was heard for two hours and 20 minutes and another for 13 minutes, suggesting that the black box (if that is what is sending out the signals) is losing battery or possibly sinking into ocean silt. Once the batteries die, officials will have very little help to direct their search — a daunting prospect, considering just how deep into the ocean the plane could have gone.