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25th March 2014, 21:54 |
#171
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Banned
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Indian Ocean sea floor under suspected MH370 wreckage unmapped and unknown
The cluster of suspected debris from Malaysian Airlines flight MH370 has been sighted above a giant undersea chain of volcanoes whose complex terrain has barely been charted, says an Australian marine geologist. Robin Beaman from James Cook University said so little of the southern Indian Ocean sea floor, including the search zone, had been mapped in detail that any attempt to retrieve wreckage would require extensive 3D mapping, likely by ships with deep ocean multibeam echo sounders. But Australia no longer has the capacity to chart depths of 3000 metres, the average depth of the search area, because the only government vessel capable of conducting mapping of that kind, the RV Southern Surveyor, had been decommissioned in December. The research vessel's replacement was being built in Singapore and was about to undergo sea trials, Dr Beaman said. ''It's bad timing really. Australia has no capability of mapping these depths,'' he said. Multibeam echo sounders send out sound pulses in the shape of a fan, returning depths of the sea floor directly under the ship and on either side, a pattern known as a swath. Dr Beaman said the first piece of debris spotted by DigitalGlobe satellites on March 16 was located about 60 kilometres south-west of the active zone of the South-East Indian Ridge, a chain of underwater volcanoes. Another object, sighted by a Chinese aircraft, was about 180 kilometres south-west of the ridge. The suspected debris spotted by an Australian aircraft on Monday was seen about 200 kilometres to the north-east of the ridge, he said. ''On the flanks of the ridge, which is very likely where any crash zone occurred, there has been virtually no … mapping apart from the odd strip,'' Dr Beaman said. Read more @ http://www.theage.com.au |
25th March 2014, 22:18 |
#172
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Banned
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The British Air Accidents Investigation Branch (AAIB) announcement:
In recent days Inmarsat developed a second innovative technique which considers the velocity of the aircraft relative to the satellite. Depending on this relative movement, the frequency received and transmitted will differ from its normal value, in much the same way that the sound of a passing car changes as it approaches and passes by. This is called the Doppler effect. The Inmarsat technique analyses the difference between the frequency that the ground station expects to receive and that actually measured. This difference is the result of the Doppler effect and is known as the Burst Frequency Offset. The Burst Frequency Offset changes depending on the location of the aircraft on an arc of possible positions, its direction of travel, and its speed. In order to establish confidence in its theory, Inmarsat checked its predictions using information obtained from six other B777 aircraft flying on the same day in various directions. There was good agreement. While on the ground at Kuala Lumpur airport, and during the early stage of the flight, MH370 transmitted several messages. At this stage the location of the aircraft and the satellite were known, so it was possible to calculate system characteristics for the aircraft, satellite, and ground station. During the flight the ground station logged the transmitted and received pulse frequencies at each handshake. Knowing the system characteristics and position of the satellite it was possible, considering aircraft performance, to determine where on each arc the calculated burst frequency offset fit best. The analysis showed poor correlation with the Northern corridor, but good correlation with the Southern corridor, and depending on the ground speed of the aircraft it was then possible to estimate positions at 0011 UTC, at which the last complete handshake took place. I must emphasise that this is not the final position of the aircraft. There is evidence of a partial handshake between the aircraft and ground station at 0019 UTC. At this time this transmission is not understood and is subject to further ongoing work. No response was received from the aircraft at 0115 UTC, when the ground earth station sent the next log on / log off message. This indicates that the aircraft was no longer logged on to the network. Therefore, some time between 0011 UTC and 0115 UTC the aircraft was no longer able to communicate with the ground station. This is consistent with the maximum endurance of the aircraft. |
6th April 2014, 11:47 |
#173
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Banned
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Report: A Chinese patrol ship detects "pulse" signal in search for Malaysia Airlines Flight MH370.
It is consistent with where this signal's frequency supposed to be found, at 37.5 kilohertz. All parties seemed to be cautiously optimistic that this is the black box signal they've been looking for since this past week. "I have been advised that a series of sounds have been detected by a Chinese ship in the search area. The characteristics reported are consistent with the aircraft black box," Angus Houston of Joint Agency Coordination Centre said. The agency had also received reports of white objects sighted on the ocean surface about 90 kilometers (56 miles) from where the electronic signals were detected. |
6th April 2014, 12:02 |
#174
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Banned
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MH370: Australia PM Abbott 'hopeful' about pulse signal
On Saturday, Chinese vessel Haixun 01 picked up a so-called "ping" signal at about 25 degrees south latitude and 101 degrees east longitude, state-run Xinhua news agency said. The signal reportedly had a frequency of 37.5kHz - the same as that emitted by the flight recorders. Three people on board the boat were said to have heard the pings, which were not recorded as they came suddenly. Xinhua also reported that a Chinese military plane had spotted a number of white floating objects about 90km away a few hours earlier. Two Chinese naval ships were reported to have joined the Haixun 01 patrol ship in the search area. "The characteristics [of the signal] reported are consistent with the aircraft black box," said retired Air Chief Marshal Angus Houston, the head of the Australian search operation, late on Saturday. "However, there is no confirmation at this stage that the signals and the objects are related to the missing aircraft." |
6th April 2014, 14:26 |
#175
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Banned
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More ‘pings’ heard in Indian Ocean, MH370 search shifts further south Three 'acoustic events' in MH370 search Retired Air Chief Marshal Angus Houston confirmed this at a press conference in Perth, according to a report on the Sydney Morning Herald. Houston said Australia’s Ocean Shield picked up the “acoustic detection” at an area some 300 nautical miles from where a Chinese vessel heard a similar electronic pulse yesterday. “It's something that needs to be investigated. The search is a dynamic thing,” he was quoted as saying in the daily. Yesterday, the Chinese ship Haixun 01 reported receiving two pulse signals at a 37.5kHz frequency, which is consistent with that of an aircraft's black box pinger, first on Friday and then again yesterday. Retired Air Chief Marshal Angus Houston, who is co-ordinating the search, told reporters in Perth on Sunday the Chinese ship Haixun 01 had detected two "acoustic events" which provided "some promise" and required a full investigation. The first signal was detected on Friday and the second, which lasted 90 seconds, was detected on Saturday within two kilometres of the original detection. “The fact that we’ve had two detections, two acoustic events in that location, provides some promise,” Houston said at a press briefing in Perth. “We’re running out of time in terms of the battery life on the emergency locator beacon.” |
Last edited by patplan; 6th April 2014 at 14:29.. |
7th April 2014, 23:46 |
#176
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Banned
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The equipment being used on Haixun 01 which detected the first two pings last Saturday is designed for local searches for divers in shallow, sheltered waters, such as harbours, hardly the tool for the job in the very deep waters of the southern Indian Ocean. The Benthos Diver Pinger listening device that they were using is designed to identify sounds at depths of less than 1,000 feet, while the ocean bottom in parts of the search area exceeds 14,000 feet. It was also reported that the Chinese did not make any recording of what they heard explained possibly by the fact that recording is not a capability of the Benthos Diver Pinger. Meanwhile, 300 nautical miles away the Australian Navy ship HMAS Ocean Shield equipped with a Towed Locator supplied by the US Navy looks to be conducting far more promising searches. Yesterday, those leading the Australian-led search effort announced that a detected sonar signal continued for two hours and 20 minutes with a second lasting for 13 minutes. On the second occasion two distinct ping returns were audible, something which was deemed to be the most promising lead yet. “Detection with the Towed Pinger Locator (TLP) is a completely different matter to that with the hand-held device. The TLP is a purpose-built detector, which is towed deep underwater to provide maximum detection range of any pinger signals,” says Winter. Even so, detecting the signal from the data recorder pinger will be highly difficult, even if HMAS Ocean Shield gets close to it. “The ocean is a very noisy place,” he says, “and there are many noise sources that can be mistaken for the pinger. Steady contact with proper equipment over a significant period of time is the only way to detect it.” The search effort will need to fix on a precise location before sending an underwater vehicle to investigate the finding, in an area of ocean whose depths are at the absolute limit of the unmanned underwater vehicle aboard Ocean Shield. Also, a phenomenon in the ocean, known as the thermocline, which acts as a horizontal acoustic mirror below the surface makes it difficult for sound to propagate from the deep ocean up through this layer. “That means that to detect pings from deep objects, you need to get below this layer, as the TPL is designed to do,” says Winter. There is cause for some optimism in the fact that search chief Air Chief Marshal Houston said there may have been the possibility that on the second run HMAS Ocean Shield detected two signals – one from each of the recorders. A slight variation in frequency between the two sonar signals could be because the pingers of the two recorders aren’t precisely the same age and their acoustic signals could vary slightly as a result. |
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