From south to north, the Indian Ocean begins at -60 degrees south latitude where it meets Antarctica’s Southern Ocean. Moving north, the Indian Ocean lies between Africa and southwestern Tasmania. It crosses Bass Strait north of Tasmania and reappears at Cape Londonderry, west of Darwin, Australia. Moving west, the Indian Ocean laps the southern shores of Indonesia’s Java Island, and the western shores of Sumatra. It extends north into and including the Bay of Bengal. On the west, the Indian Ocean includes the Red Sea, the Arabian Sea, the Persian Gulf, and Madagascar to the south. It meets the south Atlantic Ocean at Cape Algulhas at the southern tip of the African Continent.
At its widest point between southern Australia and South Africa, the Indian Ocean is about 10,000 kilometers across. It covers 74 million square kilometers of earth’s 510 square kilometer surface, meaning it engulfs 15 percent of earth’s surface.
That 15 percent was the initial and daunting scope of the search effort as investigators concluded the plane was airborne for hours, and may have flown south as far as fuel would take it: perhaps within 3,000 kilometers of Antarctica’s Southern Ocean.
Preliminary surface searches were conducted in the Gulf of Thailand and the southeastern portion of the South China Sea where it meets Vietnam and the Gulf of Thailand. There was no shortage of debris, but none of it seemed to be linked to MH370.
From the greater Gulf of Thailand region, the search crossed the Malaysian Peninsula on the second day of the disappearance, but Search and Rescue (SAR) efforts, as they were still termed at that point, were confined to Malaysia’s portion of the Straits of Malacca. Then SAR expanded again, well into the South Andaman Sea on the fourth day.
From the South Andaman Sea, the search moved quickly to the Southern Indian Ocean when it was learned that the aircraft continued to ping its 3-F1 satellite hours after it left Kuala Lumpur International Airport.
The United States National Transportation Safety Bureau helped move the search away from Malaysia when it indicated data seemed to put the plane either north or south along a long curved radius around the 3-F1 satellite extending from Kazakhstan in the north to the Southern Indian Ocean. There did not seem to be the slightest possibility the plane had gone down sooner and simply continued to ping its satellite.
And we do not know if it is even possible for a plane to go down and continue to somehow ping its satellite until batteries are depleted. But when you have a satellite network that doesn’t know earth has a Southern Hemisphere, as is the case with Inmarsat’s 3-F1 network, you have to be prepared for surprises and revelations guaranteed to amaze.
In the hope of overcoming daunting odds, it was eventually decided that the most likely terminal location along the Seventh Arc was a strip of seafloor about 1,000 kilometers long and up to 70 kilometers wide, beginning south of an ocean floor feature known as Broken Ridge. As the underwater search effort took shape, it was decided that the first step would be to conduct bathymetric mappings of the entire 60,000 square kilometer primary seafloor location.
Toward that end, Australia, which had taken day to day control of the search off of its western shore, contracted with Fugro, a Dutch firm with expertise in deep ocean surveys.
One of Fugro’s survey vessels, Equator, was assigned to do bathymetric scanning, and did some initial work north of Broken Ridge before permanently relocating to the primary search area south of Broken Ridge. Bathymetry was well on its way by October 2014 when Fugro Discovery was assigned to do some of the sidescan sonar work.
Malaysia continued to work with Australia in a limited partnership role, and separately arranged for another vessel, Go Phoenix, to assist in the search effort.
Go Phoenix was outfitted with an SLH-ProSAS-60 sidescan sonar towfish; Fugro Discovery was outfitted with an EdgeTech DT-1 towfish. The technical specifications of each were similar. Both allowed technicians aboard the vessels to monitor images in real time; both were capable of scanning seafloor widths of about 1.5 kilometers (1 mile).
Once Fugro Equator finished its bathymetric work, it was also outfitted with an EdgeTech DT-1 towfish and worked near its sister ship, Discovery, in the southern half of the search area.
Before examining the various areas covered in the surface, bathymetric, and sidescan sonar efforts, it must be said that there was no small amount of cheeky self-assurance involved in dropping vessels and crews into a sliver of ocean less than one-tenth of one percent the size of the Indian Ocean, and seriously expecting them to locate an object that “may” have flown for five hours from an unknown location in the northern hemisphere, on an unknown heading, at an unknown altitude , at an unknown speed. Did those in charge of the effort seriously believe they had a chance of finding the plane with so many unknowns? We may never know.