Australian authorities are poised to announce the next phase of the underwater search for Malaysia Airlines flight MH370 this week, five months after the plane vanished without a trace.
The Australian Transport Safety Bureau (ATSB), which is leading the search for the missing plane at the Malaysian government's request, is expected to engage a single, private contractor to search for the Boeing 777-200ER, and if successfully located, to positively identify and map the wreckage.
The operation, which the ATSB says is likely to begin in early September and will last up to a year, will include a number of underwater vehicles that will slowly scan some 60,000 square kilometers (23,000 square miles) of the southern Indian Ocean, looking for any sign of aircraft debris.
It's not yet clear exactly how the deep-sea search, which Australia has estimated will cost $56 million, will play out. While the ATSB has developed the overall search strategy, the independent contractor will be responsible for day-to-day operations in the search zone.
"We have the shape of a plan based on information we have available to us," says Martin Dolan, the ATSB's Chief Commissioner. "It's a concept we need to test out with the operation experts and come up with the detailed plan... for the conduct of the search."
Mapping the ocean floor
Some 1,800 kilometers (1,100 miles) off the coast of Western Australia, a pair of survey ships continue their efforts to give search teams a better understanding of what lies thousands of meters below the surface in one of the most uncharted, remote places on the planet.
The Chinese Navy's Zhu Kezhen and the Australian-contracted Fugro Equator have covered roughly half of the priority search area, which the ATSB says is the most likely resting place of MH370. A Malaysian survey ship is on schedule to join them in August, and underwater mapping is expected to wrap up in September.
According to the ATSB, the data collected by survey ships is being converted into detailed topographical maps. Dolan says so far those maps show ocean depths ranging from 1,500 meters to nearly 5,000 meters (roughly one to three miles), and wide-ranging terrain that includes everything from flat, sloping surfaces, to rugged terrain like mountains, ridges, and cliffs.
David Gallo, an oceanographer and director of special projects at the Woods Hole Oceanographic Institution, who was involved in the search for Air France Flight 447, says that a high level of detail is critical to make sure the search is carried out effectively and safely.
"You have to know where you're going or you'll end up impacting the bottom," Gallo says. "We're looking at less than a handful of tools that can work in this depth and that are available, so you really don't want to risk anything."
One of the most challenging spots, Gallo points out, is at the southern end of the search area, where he expects to see pockets of terrain up to 7,000 meters deep (four miles).
"The south side of that Broken Ridge is a monstrous wall... almost two miles top to bottom, almost vertical," Gallo explains, adding that there are only a few pieces of equipment worldwide that would even have a chance of reaching such extreme depths.
A slow, painstaking search
According to the ATSB's tender request, the contractor chosen to lead the search for MH370 will be required to begin the search no later than one month after signing the contract, and will be required to search all 60,000 square kilometers within 300 days.
Gallo says he expects a variety of different search assets to be used in the operation, including towed side-scan sonar devices, which are attached to a ship with a cable and can transmit data to the surface in real-time.
Robots known as underwater autonomous vehicles (UAVs) could also be used. They scan the ocean floor with similar acoustic technology but have to be brought in and out of the water, much like the Bluefin-21, which was deployed in April after search teams thought they had located pings from the plane's black boxes.
Each type of system has its strengths and weaknesses, Gallo says, noting that towed systems work well on flat terrain and cover ground quicker, while in more rugged areas, a drone which hugs the bottom will likely do a better job, albeit at a slower pace of around 65 square kilometers a day (25 square miles). For the most extreme terrain, Gallo says, search teams may need a remotely operated vehicle (ROV), steered from a surface ship with a tether.
Malaysia has already partnered with American and Australian contractors to supply additional search equipment, including a towed side-scan sonar and ROV. It's not yet clear how these will be integrated into the larger,
Where to start?
Where the search teams begin their work will depend on what the underwater maps show. "If there's a chunk of fairly smooth terrain and fairly shallow, you could get a lot of ground covered early on, which raises spirits a little bit," Gallo says.
But there's a lot of ground to cover. The area search teams hope to tackle over the next year is four times the size of the search zone for Air France 447, which went down in the mid-Atlantic in June 2009.
And with more ground to search, and potentially up to half-a-dozen search assets involved, Gallo says, the operation becomes far more complex.
"The worst thing that we could do is have a ship show up with technology, have them go over the spot...and you write that spot off forever."
But Gallo adds that he is completely confident in the ATSB's ability to manage the overall operation and says that if the wreckage of MH370 is in the designated search zone, it will be found.
Are they looking in the right place?
There is far less confidence about whether search teams are looking in the right spot. The search for MH370 continues to focus along the seventh arc, the so-called "partial handshake," which experts believe was the last signal sent between the Malaysia Airlines plane and a communications satellite operated by Inmarsat.
"What I'm a little concerned about... is that there still seems to be some confusion about Inmarsat data and how it's being interpreted," said David Soucie, a former safety inspector at the U.S Federal Aviation Administration and author of "Why Planes Crash."
In late June, the ATSB announced it was moving the priority search area several hundred kilometers southwest, the second major shift of the search zone along the arc. That move was based on analysis of the satellite data and a review of aircraft performance limits, including speed and altitude, by an international group of experts.
That analysis also made a series of assumptions, "in order to define a search area of practical size," the ATSB's June report says, including that the plane was flying on autopilot for a long period of time until it eventually ran out of fuel and crashed. Not making that assumption, the report says, "would result in an impractically large search area."
The ATSB's Dolan says that the Inmarsat data will continue to be reviewed during the next phase of the search. And the bureau says there is still a chance the search may be extended outside the 60,000 square kilometers designated as the priority area.
"The haystack is a big chunk of terrain in the Indian Ocean," Gallo of Woods Hole says. And even though the haystack is huge there's no guarantee that the needle is in that haystack."
Soucie agrees, however, he adds the ATSB is going about the search in a smart way. "Am I confident they will find the airplane in that area? No. But if it were my search, I would be doing exactly what they're doing.
Despite a potentially vast search zone, Dolan says he's cautiously optimistic search teams will find the missing plane "We're doing this, in a large part, because we want to give some certainty to those who are grieving the loss of their loved ones, and we're fully committed to doing that."
MH370 departed Kuala Lumpur for Beijing early on the morning of March 8 carrying 239 passengers and crew. On March 24, Malaysian Prime Minister Najib Razak announced that the flight had ended in the southern Indian Ocean.
To date, no trace of the plane has been found.