GeoAcoustics – Topas
TOPAS PS18 is designed for sub-bottom profiling with very high spatial resolution in water depths from less than 20 metres to full ocean depth. The +80% relative bandwidth, low frequency signal is generated in the water column by non-linear interaction between two high frequency signals (centred symmetrically around 18 kHz). Similarly, a sum frequency signal is also generated. However, only the low frequency signal is used for sub-bottom profiling.
| SYSTEM SPECIFICATIONS | |
| The Kongsberg TOPAS PS 18 parametric sub-bottom profiler comprises the following units: | |
| UNITS | |
| • Transducer – 8 x 16 channels | |
| • Transceiver Unit – Linear, switched mode power amplifier – Built-in T/R-switch – Low noise receiver with 24 bit ADC – High dynamic range; >110 dB | |
| • Operator Console – MMI – Real-time processing – PC-based platform (Windows) | |
| • Optional – Multi-channel receiver (MCR) and beamformer | |
| PARAMETRIC SOURCE CHARACTERISTICS | |
| The parametric sources have the advantage of generating a low frequency signal beam with no distinct sidelobe structure. The beam tapers off smoothly, reducing the possibility of spurious signals due to sidelobes in the received signal. | |
| The transducer is hull mounted. This removes the need for deployment or recovery of tow-fishes during survey operations, resulting in more efficient survey time and higher positioning accuracy for the profile. Manoeuvrability of the vessel is also improved. | |
| In a “low noise” vessel, excellent profiling results are achieved even at survey speeds of +14 knots. | |
| SIGNAL MODES | |
| The system can operate with various signal waveforms for optimum performance: | |
| Ricker pulses are used for very high resolution work. | |
| Chirp pulses are used for deep water, high penetration work. | |
| CW pulses are used for narrow band, frequency sensitive work. | |
| STABILISATION & BEAM CONTROL | |
| The transmitted beam is electronically stabilised in roll, pitch and heave (requires input from a vertical reference unit), ensuring that the insonified area on the sea floor is accurately positioned. | |
| The transmitter can be used in a sequentially beam steering mode covering a larger sector. This is of importance in object detection and location applications. | |
| PENETRATION PERFORMANCE | |
| Penetration performance depends on sediment characteristics, water depth, transmitted signature and noise level. | |
| Penetration of more than 200 metres has been achieved in water depths of more than 3,800 metres with a sediment layer resolution of typically 15 cm or better. |
| SYSTEM SPECIFICATIONS | |
| The Kongsberg TOPAS PS 18 parametric sub-bottom profiler comprises the following units: | |
| TRANSDUCER | |
| 8 x 16 channels | |
| TRANSCEIVER UNIT | |
| Linear, switched mode power amplifier | |
| Built-in T/R-switch | |
| Low noise receiver with 24 bit ADC | |
| High dynamic range; >110 dB | |
| OPERATOR CONSOLE | |
| MMI | |
| Real-time processing | |
| PC-based platform (Windows) | |
| OPTIONAL | |
| Multi-channel receiver (MCR) and beamformer |
| TECHNICAL SPECIFICATIONS | |
| TYPICAL SPECIFICATION | |
| Primary Frequency | 15 – 21 kHz |
| Secondary Frequency | 0.5 – 6.0 kHz |
| Output Power | >32 kW |
| Beamwidth – Primary | ~3.5 deg |
| Beamwidth – Secondary | ~4.5 x 4.5 deg |
| Source Level (4 kHz) | ~209 dB / 1 μPa @ 1 m |
| Dynamic Range | >110 dB |
| Range Resolution | <0.15 m |
| Penetration Capability | >200 m |
| Depth Range | <20 – >11,000 m |
| Beam Steering | 80 / 20 deg (across / along) |
| REAL-TIME PROCESSING | |
| Digital band-pass filter | Spiking deconvolution / Matched filter | Time Varying Filter (TVF) | Bad trace removal | Dereverberation | Time Variable Gain (TVG) | Automatic Volume Control (AVC) | Stacking (Trace mixing) | Swell filter | Manual/automatic gain | Attribute processing | Statistics | Power Spectral Density (PSD) display | |
| ADDITIONAL OFF-LINE PROCESSING | |
| Synthetic Aperture Sonar processing (SAS) | Interpretation / Digitization of interfaces | TOPAS tracks displayed / selected in SIS | |
| DIMENSIONS & WEIGHT | |
| Transceiver: 600 x 756 x 1188 mm, 170 kg | Transducer array: 1142 x 1140 x 260 mm, 525 kg | |
| SYSTEM INTERFACES | |
| Navigation input – NMEA 0183 (RS232/UDP) | Depth/slope input – NMEA 0183 (RS232/UDP) | Ethernet | Printer/recorder – analogue/digital | VRU (RS422/RS232) | Synchronizing unit (K-Sync) – TTL | |