Please cite this dataset as follows:

Larter, R., Hogan, K., Hillenbrand, C.-D., & Gowland, E. (2021). Topographic Parametric Sonar (TOPAS) acoustic sub-bottom profiler data acquired on RRS James Clark Ross JR298 cruise in 2015 (Version 1.0) [Data set]. NERC EDS UK Polar Data Centre. https://doi.org/10.5285/BDFEB69C-DF5C-461D-B7A8-583F9DAAB685

Methodology:

These data were collected using a Kongsberg Simrad TOPAS PS018 acoustic sub-bottom profiler. The TOPAS system operated by transmitting a chirp pulse with a frequency band of 1.5-5kHz and length of 10 ms. The receiver had a sample rate of 20 kHz with a trace length of 400 ms, and the gain (in dB) was controlled by the sonar watchkeeper with a range of 2-15 dB and a high-pass filter of 1-2 kHz .

Logging of sub-bottom profiler data began at 1514 UTC on Julian day 032, and the system was operated near-continuously during the cruise until 1208 UTC on Julian day 058 when the JCR was approaching Rothera.TOPAS was re-started at 1014 UTC on Julian day 059 and was run until a location in the Drake Passage, 200 nautical miles from the coast at the edge of Argentina's exclusive economic zone. Pinging and logging of TOPAS sub-bottom profiles was stopped for the final time at 1756 UTC on Julian day 060.

Additional settings information can be found in the cruise report: https://www.bodc.ac.uk/resources/inventories/cruise_inventory/reports/jr298.pdf

Data collection:

Data were collected using a Kongsberg Simrad TOPAS PS018 sub-bottom profiler

Data quality:

A swept-frequency ("chirp") transmission pulse was used, which required the return signals to be cross-correlated with the source signature (matched filter) throughout the cruise to extract signals with a simple effective waveform, which also has the benefit of reducing random noise (see more information in the cruise report: https://www.bodc.ac.uk/resources/inventories/cruise_inventory/reports/jr298.pdf )