Six months ago, Malaysia Airlines flight 370 disappeared with 239 passengers on board after departing from Kuala Lumpur. After an initial frantic search to find the Boeing 777's black boxes before their batteries petered out, rescue crews called off efforts and began a major undertaking to map the seafloor. Now, four months later, those maps are complete, and the search is beginning anew this month as three ships plan to scour the search area for debris by dragging a sensor device just 330 feet (100 meters) above the seabed at a speed of seven miles per hour, according to the Associated Press.

The device, known as a towfish, is equipped with sonar to produced detailed imagery of the ocean floor, and they are tethered to the ships with six-mile cables. They also have jet fuel sensors on board, and crews can lift the devices and attach a video camera to investigate regions of particular interest.

The first ship is set to reach the search area, in a far-flung, previously unmapped stretch of the south Indian Ocean, tomorrow. Two additional ships, paid for by the Australian government, will join the first Malaysia-provided vessel in a few weeks' time. The search area encompasses a strip of ocean covering some 23,000 square miles. The final satellite pings from the flight led search crews to focus on the area, known as the "seventh arc." Both governments are said to be providing roughly $60 million to aid in the search.