The mystery of the missing Malaysia Airline flight MH370 is closer to being solved as authorities have revealed that they have tracked the final unexplained signal emitted by the jet, to the same point in the Indian Ocean, where the jet was believed to have crashed. Time will tell whether this is a definitive lead […]
The mystery of the missing Malaysia Airline flight MH370 is closer to being solved as authorities have revealed that they have tracked the final unexplained signal emitted by the jet, to the same point in the Indian Ocean, where the jet was believed to have crashed. Time will tell whether this is a definitive lead or a false alarm. We all hope it is the beginning to a successful answer.
Calling the latest development a promising lead, retired Air Chief Marshal Angus Houston, who is leading the search, said that an Australian navy ship had detected two sets of pulse signals that sounded just like an emergency locator beacon.
While the first set was heard on Saturday and lasted for two hours and 20 minutes, the Ocean Shield ship then lost contact with the “pings” but turned around and later heard further signals for 13 minutes, the Sydney Morning Herald reported.
However, the ship lost contact again and has been trying to relocate the signals.
Houston said that in the search so far it is probably the best information that the team has had, adding that the search team is encouraged that it is very close to where it needs to be.
He added that he would want more confirmation before he could say ‘this is it’.
Here is a list of the equipment that is being employed by the searchers.
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1. Beacon Black Box Locator Acoustic 37.5 KHz Pingers
An underwater locator beacon (ULB) or underwater acoustic beacon, also known informally as a pinger, is a device fitted to aviation flight recorders such as the cockpit voice recorder (CVR) and flight data recorder (FDR). ULBs are also sometimes required to be attached directly to an aircraft fuselage. ULBs are triggered by water immersion; most emit an ultrasonic 10ms pulse once per second at 37.5 kHz ± 1kHz.
Maximum detection range
A 37.5 kHz (160.5 dB re 1 μPa) pinger can be detectable 1–2 kilometres (0.62–1.24 mi) from the surface in normal conditions and 4–5 kilometres (2.5–3.1 mi) in good conditions. A 37.5 kHz (180 dB re 1 μPa) transponder pinger can be detected 4–5 kilometres (2.5–3.1 mi) in normal conditions and 6–7 kilometres (3.7–4.3 mi) in good conditions.
• Operating Frequency: 37.5 kHz Â ± 1 kHz (Doppler can shift the measured frequency)
• Operating Depth: Surface to 20,000 feet (6100 m or 3.33 nmi)
• Pulse Length: Not less than 9 milliseconds (10 millisecond nominal)
• Pulse Repetition Rate: Not less than 0.9 pulse per second (1 pulse per second nominal)
• Acoustic Output, Initial: 1060 dynes/cm2rms pressure at 1 meter (160.5 dB re 1 UPa/ meter)
• Acoustic Output, After 30 days: 700 dynes/cm2rms pressure at 1 meter (157.0 dB re 1 UPa/meter or about 70 % of the nominal range as it degrades)
• Radiation Pattern: Rated output over 80 percent of sphere, near omni-directional
• Size: 1.3″ diameter x 4″ long (DK100/DK120)
• 1.3″ diameter x 2.97″ long (DK130/DK140)
• Weight: Less than 7 oz (including battery) (DK100/DK120)
• Less than 4.9 oz (including battery)(DK130/DK140)
• Power Source: Lithium Battery
• Expected range: about 2 nmi slant range radius from source for 37.5 KHz
Expected Transmission Loss at 37.5 Khz assuming absorption of 4.2 dB per KIM plus spreading loss of 20 log R or 60 dB + 10 log r for R> 1000 meters
37.5 KHz ———————— 0.31 mi .62 mi 1.25 mi 3.25 mi 6.2 mi 10 mi 100 mi mi
Range in KM ———————— 0.5 1 2 5 10 16 160 KM
TL =20 log Rkm*1000+ alpha*Rkm 56.1 64.2 74.4 95.0 122.0 151.3 776.1 TL (dB)
TL =20 log Rkm*1000+ alpha*Rkm for RKM <1 Km 56.1 64.2 71.4 88.0 112.0 139.2 754.0 TL (dB)
TL =60 +10*log Rkm+ alpha*Rkm for RKM.>1
2. Autonomous Underwater Vehicle – Bluefin-21 Search Vehicle
The Bluefin-21 is a highly modular autonomous underwater vehicle able to carry multiple sensors and payloads at once. It boasts a high energy capacity that enables extended operations even at the greatest depths. The Bluefin-21 has immense capability but is also flexible enough to operate from various ships of opportunity worldwide.
EdgeTech 2200-M 120/410 kHz side scan sonar for search
Reson 7125 400 kHz multibeam echosounder for site mapping
3 Side Scan Sonar Option – EdgeTech 2200
The Full Spectrum chirp side scan sonar is a calibrated wide band digital FM sonar that provides quantitative and qualitative, high resolution, low-noise side scan imagery. It simultaneously transmits linearly swept FM pulses and the user may select the combination of these frequencies dual simultaneous as follows:
120/410 kHz, (most likely for Malaysia Airline Flight 370 Search)
75/120 kHz or
A Digital Signal Processor (DSP) in the Full Spectrum (FSDW) electronics on the AUV or ROV holds the two chirp waveforms to be transmitted.
ATI thinks the side scan frequency is likely to be 120/410 KHz which will give ranges of 250 m to 500m at 120 KHz and 130M to 200m at 400 Khz.
That will imply short detection ranges even for the 120 KHz sonar, say 250 – 500 m per side. The 410 KHz is then used at shorter range (130 – 200 m) to get a higher resolution image. The search pattern must overlap to leave no coverage holes, so the offsets in range between passes may be at most 90 percent of the assured range.
Expected Operational Ranges for the EdgeTech 2200- side scan sonar, depending on Water temperature and salinity. The absorption factor is estimated based on a model from Francois and Garrison, JASA 1982, and a depth of 50m. Absorption decrease slightly as the side scan is towed deeper. The range is to each side and the search rate is likely to be limited to 2.5 or 3.0 knots to keep the autonomous underwater vehicle (AUV) near the bottom on a long cable scope.
Quoted from http://www.edgetech.com/docs/app_note_range.pdf
||14,763 ft (4,500 m)
||25 hours @ 3 knots with standard payload
- Freq : 120Khz, Range: 250 to 500m
- Freq: 410kHz, Range: 130 to > 200m
4. SeaBat 7125 – Reson 7125 400 kHz multibeam echosounder
The fundamental acoustics with 400 kHz for high resolution, high density surveying which exceeds the most stringent of specifications, and 200kHz for greater range performance. The SeaBat 7125 can be installed on any platform from survey vessels to ROVs and AUVs down to 6000m water depth.
The 400 kHz multibeam echosounder is a multibeam mapping sonar. ATI would expect that it will need to be towed about 150 – 400 m off the bottom to get good signal to noise. It is likely used to map the wreckage after it has been found using the side scan sonar.
Then ATI expects some short range video to confirm and map the wreckage.
- Freq : 75kHz, Range: 700 to 800m. 1000m is possible at extreme depths and with special pulses
- Freq : 270kHz, Range : 150 to 300m
- Freq : 540kHz, Range: 100 to 150m
- Freq : 850kHz, Range: 50 to 75m