Hull Mounted Sonar Flashcards
What is the purpose of HMS?
To provide STJ with an active and passive sonar system to detect, track, localize and classify surface and sub-surface targets.
Active noise limiting sonar equation
SL + DI_t + TS - 2TL - (NL - DI_r) > DT
Active reverb limited sonar equation
SL + DI_t + TS - 2TL - NL - RL > DT
How many SETs are there
360 arranged in vertical stacks of ten SETs per STAVE.
What are the transmit frequencies?
6.4, 7.2, 8.9 kHz
What are the receive frequencies?
2.2 - 5.5 kHz (Active)
2.2 - 8.6 kHz (Passive)
What is the output power?
1.2 kW per stave (43.2 kW total) in high
316 W per stave in low power
How many active and passive track?
64 active
36 passive
What is the range of HMS?
9 nautical miles
What is the beam width?
Omni: 360 degrees
DT Wide: 30 degrees
DT Narrow: 10 degrees
What is the purpose of the operators console?
This is the HMI for the system. It is a dual display system with an audio jack. Target classification is performed here.
What is the purpose of the instructors console?
This is a laptop where operators can upload scenarios and synthetic targets for training purposes.
What is the purpose of the data recorder?
This is a magnetic tape recorder where you can store up to 24 hours of unprocessed audio data. This could be used later with the instructors console for training.
What is the Sonar Control Cabinet (SCC)?
This is where main control of the system is performed. It is made up of the Sonar Control Assembly (SCA) and the Sonar Interface Assembly
What is the Sonar Control Assembly (SCA)?
This is a series of CCAs responsible for control, operation, display, detection and tracking. Additionally, there is a database of active and passive tracks stored here.
What is the Sonar Interface Assembly (SIA)?
This controls the generation and transmission of the active ping signal. It also receives the incoming acoustic signals, digitizes them and sends them to the SCC for further processing and distribution.
What is the purpose of the High Speed Signal Processor (HSSP)?
This receives acoustic data from the SIA in normal mode or the data recorder in replay mode. It also provides simulated outputs in training mode.
The HSSP performs Fast Fourier Transforms (FFT) to shift signals from the time to frequency domain for spectrum analysis.
What is the purpose of the maintenance console?
This connects to the SCC to run diagnostics, upload software and display a fault log.
What is the purpose of the maintenance console?
This connects to the SCC to run diagnostics, upload software and display a fault log.
What is the purpose of the Junction Box Interconnect?
It interfaces the Transmitter Group, SCC and C5 main control panel. It is a main controller for the system and tells the SCC the transducer position.
What is the purpose of the Junction Box Interconnect?
It interfaces the Transmitter Group, SCC and C5 main control panel. It is a main controller for the system and tells the SCC the transducer position.
What is the Sonar Transmit Unit
The transmit unit consists of seven drawers.
One drawer is the Integrated Test Equipment
The other six drawers are called Transducer Driver Assemblies (TDA). In each TDS, there are six Sonar Power Inverters (SPI) for a total of 36 (one per stave). Each is capable of amplifying an incident signal to 1.2kW
What is the purpose of the TR switch?
It is a 36 solid state switches that allow the passage of transmit or receive signals.
Define the transducer
The transducer is comprised of 360 Single Element Transducers arranged in vertical stacks of ten SETs per STAVE. There are 36 staves that provide 10 degrees of azimuth coverage each for a full 360 degree.
What is the sonar dome?
The sonar dome is the housing for the transducer. It is fitted to the hull of the ship and is filled with sea water for impedance matching.
What is the purpose of the Main Control Unit?
It is misnamed as the main controller of the system. You can use it to raise or lower the transducer, and see the status of the transducer.
What is the purpose of the Alternate Control Unit?
This is where the transducer is actually controlled from. You can raise and lower and see status from here.
What is the sonar hull outfit?
This is a 5hp motor used to raise and lower the transducer. In the event that the motor fails, you can use the handwheel as a back up.
What are the modes of HMS operation?
Active - Transmitting acoustic energy in the 2.2-5.5 kHz range and processing the returns.
Passive - Listening in the 2.2 -8.6 kHz range and processing the returns
Normal - Collecting acoustic information and presenting it to the operator. This is the default mode.
Replay - Processing and displaying acoustic data stored in the data recorder.
Training - Using the instructors console to simulate an environment for training. You can also use the replay mode here to superimpose actual recorded data to the simulation.
Diagnostic - Used to fault detect and isolate.
What are the HMS System interfaces (6)
1) EPG&D
2) HVAC
3) CMS
4) NDDS for GPS and attitude (AUX B)
5) UWT for blanking
6) Bridge Panel for status
What are the HMS redundancy and survivability considerations (6)
1) Can operate in standalone if CMS is lost
2) Two SETs/stave can be lost and maintain functionality
3( 35 SETs can be lost in total
4) Transducer can be lowered by hand if the motor fails
5) Some parts can be used from the HSSP in CANTASS
6) Transmitter assembly drawers are interchangeable if do get desired STAVE arrangement.
7) Battle short to override environmental restrictions.
What are the HMS safety considerations?
1) General electrical safety
2) Divers down precautions (keys)
3) MMM (NAVORD 4003-6)
4) Interlocks when a drawer is opened
5) Down locks that prevent Tx unless transducer is fully down.
What are the HMS test and trial considerations?
1) Integrated tests
2) Sonar performance figure trials in three parts.
3) HATS conducted by UWSE
What are the ocean layers?
1) Surface layer
2) Seasonal Thermocline
3) Permanent Thermocline
4) Deep Isothermal Layer
What are the six sound propagation paths through water?
1) Surface ducting
2) Secondary Sound Channel
3) Convergence Zone
4) Bottom Bounce
5) Shadow Zone
6) Direct Path
What is surface ducting?
Sound waves stuck between surface layer and seasonal thermocline
What is the secondary sound channel?
This is where the surface layer meets the seasonal thermocline.
What is the Convergence Zone?
Sound is reflected off the deep isothermal and converge to a small area at the surface.
Define the shadow zone
Where the speed of sound changes at the permanent thermocline and sound is randomly reflected.
What factors affect UW signal propagation?
1) Temperature
2) Salinity
3) Pressure (depth)
Define the deep sound channel
This occurs at the point where the speed of sound has reached its minimum value before steadily increasing.
How does beamforming work?
A series of signals are sent out and they are slightly time shifted relative to each other. As the signals constructively and destructively interfere, they create an incident beam that is transmitted in the desired direction.
In receiving, sound will be picked up by different hydrophones at different times and angles. Applying time delays, means we can steer the focus to where the sound originated.
How many SETs and STAVES can be lost and still be operational
1) 35 SETs
2) 3 STAVES
Can you isolate a stave? What is a tie back?
Yes, you can tie back a set/stave by routing them to a dummy load.
There are six Sonar Power Inverters (SPI), what is their purpose?
Each SPI powers a stave on the transducer amplifying 1.2kw of total power. The SPIs are located in drawers in the transmitter cabinet. There are six SPIs per drawer for a total of 36.
What is a SET?
A ceramic piezoelectric device in a ring shape between two plates. When current is applied, the disc deforms sending acoustic energy into the water. When it receives sound, it vibrates, creating an electrical signal.
How can HMS push a track to CMS?
After three sweeps a track is created on HMS. Once this happens, an operator can push the track to CMS to be used by the UWWO.
What reference governs confined space entry?
SEMS S08
Describe a Fast Fourier Transform
FFT takes a time domain signal and converts it to a frequency domain signal. From this, we can identify the frequencies in the signal, and eliminate the noise. This process is reversed for listening and display purposes.
Where are the outfit limit switches?
Located at the top and bottom of the transducer travel path. They indicate when the transducer is full up or down.
What does ASPO stand for? Where do they sit?
1) Anti-submarine plotting operator
2) Front row, STBD side
What equipment is used to test the SETs?
VIP 250
What are the transmission limitations?
1) Greater than 5 degrees or roll
2) Greater than 0.08 G of roll or pitch acceleration
3) Equivalent to sea state 6 or cresting a 15 foot wave.
What are the different types of scans we can use?
1) A Scan - Amplitude vs range - used for detection.
2) B-Scan - Amplitude vs range vs bearing - used to monitor target motion.
3) C Scan - Displays the signal strength vs range. Used with DT Narrow
4) D Scan - Signal strength vs target doppler by omnidirectional CW ping
5) T Scan - Like B Scan with expanded range and width
6) P Scan - Displays passive data for the last 11 minutes in 10 degree segments (used for torpedo detection)
7) Noise Field Monitor - displays noise estimates for each beam.
What is a SPF 1?
Done alongside to determine transducer operation.
What is a SPF II?
Done in the basin with a test bed boom to test transmitter and receiver function.
What is a SPF III?
Done at sea to determine the self noise vs speed
What is a SPF?
Sonar Performance Figure - give sonar range for given conditions.
Why are the ranges for passive and active different?
With active you’re depending on the power of your output, the target strength and the losses going both ways.
How does HMS get MET information?
Through CMS to the SCC
How many tracks can the system handle?
1) 100 total (64 active, 36 passive)
2) 84 auto and 16 manual
3) 8 can be sent to CMS
Can you hear further than the 9 NM range.
You can use the convergence zones. How effective that it? No idea.
Why do we have 3 transmit frequencies?
To operate multiple HMS in the same area.
How many staves are used for DT wide and narrow?
14 each
What SETs if lost will immediately render HMS U/S
SETs in a cross formation
Why is 115V 400Hz required for HMS
What information is on the bridge panel other than the transducer being up or down?
Name ALL the system safety interlocks
Are there any issues with going straight to high power?
You should progress from low power first.
Can SETs be interchanged?
In theory, yes, but the process would be daunting.
Explain how the reverse waterfall display works
Why is there a GPS feed for HMS?
What is ADAC?
Acoustic Data Analysis Center
How do we classify targets?
What does the CMS symbology for a submarine look like?
It’s an upside down house with an expanding circle around it. The circle indicates an area where the sub could be. The larger the circle, the larger the potential location area.
What is a torpedo limiting line?
How does ASW appear on CMS?
What are reverberation losses?
Reverberations are the losses that occur close to the sonar due to reflections. They could be reflections off the sea floor, mammals, cavitation.
What is the detection threshold?
