The Australian Transport Safety Bureau (ATSB) is leading the underwater search for missing Malaysia Airlines flight MH370. All the available data indicates the aircraft entered the sea close to a long but narrow arc of the southern Indian Ocean.
The search is a complex operation that will involve a range of vessels, equipment and expertise to cover 60,000 square kilometres of ocean floor.
During the first stage of the search, the ATSB is tasking a Chinese PLA-Navy ship to undertake a bathymetric survey of the 60,000 square kilometre search area. A contracted commercial vessel with join the survey in June. The bathymetric survey will provide a map of the underwater search zone, charting the contours, depths and hardness of the ocean floor.
While the ocean depth of the search zone is understood to be between 1000 m and 6000 m, we currently have very limited knowledge of the sea floor terrain facing the underwater search operation. The information we receive from the bathymetric survey will give us crucial data to plan and conduct the intensified underwater search.
How the survey’s done
The operation will involve a ship surveying the ocean floor using multi beam sonar, which is capable of collecting high quality data to water depths of up to 6,000 m.
Multibeam sonar is a common offshore surveying tool that uses multiple sound signals to detect the seafloor. Due to its multiple beams it is able to map a swath of the seabed under the ship, in contrast to a single beam sonar which only maps a point below the ship. Different frequencies are used to map different water depths, with higher frequencies (>100kHz) used for shallow water and low frequencies (<30 kHz) for deep water.
Generally, the multibeam sonar transducer is mounted rigidly to the hull of the survey vessel and its position can be calculated very accurately. Other parts of the multibeam system include auxiliary sensors such as motion-sensing systems and Global Positioning Systems (GPS) to ensure accurate positioning, motion sensing and sound speed measurement system.
A modern multibeam sonar transducer typically uses the Mills Cross telescope array. The sound is transmitted from transducers that are perpendicular to the survey track. Consequently, the sound pulses forms a transmit swath that is wide across-track and narrow along-track. The returning sound pulses, which are mainly recording the impedance contrast and seafloor topography, are received by the receivers which are mounted parallel to the survey track. These return beams are narrow across-track. Unlike the sidescan sonar which commonly produces only acoustic backscatter data (i.e. hardness), the multibeam sonar generates both water depth and seafloor hardness data concurrently.1
How many vessels will be involved in the survey
The Chinese PLA-Navy ship Zhu Kezhen (872) is already in the search area conducting a bathymetric survey of an area provided by the ATSB. A contracted survey vessel will arrive in the search area in early June.
How long it will take
It is expected that the bathymetric survey will take around three months to complete, but this will depend on a number of factors, such as weather conditions, during the survey operations.
The underwater search will begin when we have enough data from the bathymetric survey to start searching. This means that the underwater search will begin while the survey is still being completed.
More information on bathymetric surveys can be found on the Geoscience Australia website at www.ga.gov.au
1 Multibeam Sonar, Geoscience Australia
|Type:||Educational Fact Sheet|
|Publication date:||26 May 2014|
The Australian Transport Safety Bureau continues to refine the area where the aircraft entered the water based on ground-breaking and multi-disciplinary technical analysis of satellite communication and aircraft performance, passed from the international air crash investigative team comprising analysts from the United States, the United Kingdom and Australia.
All the available data indicates the aircraft entered the sea close to a long but narrow arc of the Indian Ocean. Prioritising the most probable search area along this arc is the focus of current activities.
The Australian Government accepted responsibility for search operations in the southern Indian Ocean on 17 March 2014.
The initial activities involved a surface search of the southern Indian Ocean for floating debris and a sub-surface search for the aircraft black boxes.
The surface search was coordinated by the Australian Maritime Safety Authority (AMSA), supported by the Australian Defence Force and other agencies.
The initial search phase involved 22 military aircraft and 19 ships, covering search areas of more than 4.6 million square kilometres. Civilian aircraft contracted to AMSA also participated in the search.
- MH370 Facts and Statistics—Surface Search of the Southern Indian Ocean PDF: 39 KB
The Australian Transport Safety Bureau has been leading, in consultation with Malaysia and China, the review and analysis of all data and information relating to the likely flight path of MH370, together with information acquired in the course of the search to date.
A bathymetric survey of the areas of the arc commenced in May. The bathymetric survey—or mapping of the ocean floor—is being done in preparation for the underwater search.
Further information is available here.
The underwater search will involve a comprehensive search of the sea floor for a debris field and will utilise towed vehicles equipped with side scan sonar, synthetic aperture sonar, multi-beam echo sounders, with video cameras available to be deployed to locate and identify MH370.
This activity will need to be operated from specialised vessels by teams of qualified experts. On 6 August 2014, Australia awarded a contract to Fugro Survey Pty Ltd (Fugro) to conduct a search of the southern Indian Ocean sea floor for missing Malaysia Airlines flight MH370.
The ATSB is leading the search using vessels funded jointly by Malaysia and Australia, including Fugro Discovery, Fugro Equator (which is currently being used to survey the search area) and GO Phoenix.
Once the search enters the underwater phase, the search of the priority areas is anticipated to take up to 12 months to complete.
Please see the ATSB website for further fact sheets on the search for MH370.
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