It is conventional to use research and fishing vessels as ships of opportunity to collect acoustic data at basin scales throughout the oceans (e.g. http://imos.org.au/facilities/shipsofopportunity/bioacoustic/). Unfortunately this data can only be collected as part of other ship missions and will have both spatial and temporal limitations. Recently the development of unmanned science vehicles (USV) is opening up new opportunities to collect atmospheric, oceanographic and acoustic data remotely with real time summary data available. The wind powered Saildrone (www.saildrone.com ) is an example of these USV’s that have been equipped with a range of metrological, oceanographic and acoustic sensors (see photo and schematics)

Saildrone instrumentation (credits CSIRO)

Saildrone instrumentation (credits CSIRO)

Saildrone characteristics and instrumentation

Length: 7 m
Height: 5 m
Depth: 5.5 m
Speed: transit 3 Kt, max 8 Kt
Payload power: 30 W steady state
Payload capacity: 250 lbs
Max deployed duration: 12 months

Atmospheric measurements

(1) Wind speed and wind direction
Anenometer @+ 5 m
(2) Radiations
Photosynthetically active radiation (PAR) @+2.2 m
(3) Radiations
Sunshine Pyranometer @+2.2 m
(4) Air temperature and Relative humidity
Meteorological probe @+2.2m
(5) Pressure
Digital barometer @+0.2 m
(6) pCO2
Atmospheric pCO2 @+0.2 m

Physical measurements

(8) Wave height and period
Dual GPS-aided IMU
(15) Depth
SIMRAD Echo sounder @-2.5 m

Maritime Domain Awareness

(16) Surface cameras
360 deg cameras Saildrone custom
(17) AIS
AIS transceiver

Ocean measurements

(9) skin temperature
SST IR Pyranometer @+2.2 m
(10) pH
pH sensor @ -00.5 m
(11) Chl-A, CDOM concentration, Red Backscatter
Fluorometer @-0.2 m
(12) Dissolved oxygen
Oxygen optode @-0.5 m
(13) pCO2
Dissolved pCO2 @-0.5 m
(14) Water temperature, Salinity
Thermosalinograph @-0.5 m
(15) Acoustic backscatter
SIMRAD Echo sounder @-2.5 m

During recent southern ocean trials by CSIRO it has been demonstrated that the performance of the acoustics exceeded expectations. The low power wide beam 38 kHz transducer could detect scattering layers to 1000 m due to the low vessel noise. Example of raw acoustic data below during a day – night day cycle highlights the biological scattering layers and migrations from 300 to 1000 m during the day to the upper 200 m depth range during the night. This demonstrated that the vehicles with the current acoustic instruments can be used for studying the mesopelagic ecosystems of the global oceans and the flux of biology (carbon) from mesopelagic and epipelagic depths. Currently summary data is provided from the acoustics in real time with the raw data stored on the vehicle for later download and processing. Conceivably in the near future more processing of multi-frequency or broadband data could be done in the vehicles with machine learning and artificial intelligent algorithms sending back a range of meaningful biological metrics in real time. These metrics could then be assimilated into carbon and ecological models using the framework developed within the EU MESOPP program.

Example of raw acoustic data from the Saildrone 38 kHz acoustic system collected during a day – night day cycle to 1000 m depth highlighting the biological scattering layers and migrations from mesopelagic 200 to 1000 m to the upper 200 m epipelagic depth range (Credits CSIRO)

Example of raw acoustic data from the Saildrone 38 kHz acoustic system collected during a day – night day cycle to 1000 m depth highlighting the biological scattering layers and migrations from mesopelagic 200 to 1000 m to the upper 200 m epipelagic depth range (Credits CSIRO)

Rudy Kloser, CSIRO, 2019/04/04

See also:

and