2021 EM 304 Sea Acceptance Testing and Mapping Shakedown

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From April 16 - May 10, 2021, NOAA Ocean Exploration conducted acceptance testing of a state-of-the-art EM 304 MKII multibeam sonar transducer and ensured that all mapping-related equipment aboard NOAA Ship Okeanos Explorer were calibrated and functional for 2021 operations. This expedition was expected to be challenging due to the high stakes EM 304 Sonar Acceptance Testing (SAT), the EK80 38 kHz split-beam transducer acceptance, shake down of the systems after an intense drydock and remobilization period, and the fact that it was the first expedition on Okeanos Explorer since March 2020.

Despite these challenges and additional unforeseen obstacles that arose during the expedition, all of the rigorous objectives that were planned were completed and much more! Along with the shakedown objectives, a focused survey was completed to explore and map approximately 6,000 square kilometers (2,317 square miles) on the Blake Plateau, where new mapping data have been transforming scientific understanding of the marine habitats in the region.

Below is a summary of the primary achievements during the 2021 EM 304 Sea Acceptance Testing and Mapping Shakedown expedition.

• 22,200 square kilometers (8,570 square miles) mapped. This includes an approximately 6,000-square-kilometer focused survey on the Blake Plateau. A total of 18,700 square kilometers (7,220 square miles) were mapped within the U.S. Exclusive Economic Zone deeper than 200 meters (656 feet), contributing to the National Strategy for Mapping, Exploring, and Characterizing the United States Exclusive Economic Zone and Seabed 2030 goals.
• Completion of Kongsberg's required SAT objectives and additional recommended tests suggested by the Multibeam Advisory Committee. This included a GNSS Azimuth Measurement Subsystem (GAMS) Test, geometric calibration (“patch test”), speed-noise test, coverage extinction testing, backscatter normalization, and five accuracy surveys in five different depth ranges.
• Acceptance of the Kongsberg EM 304 MK II Transmit Array. This is the first complete EM 304 MKII array in the field! This advancement will likely lead to increased mapping efficiencies as compared to the previously installed EM 302.
• Acceptance of the new EK80 38 kHz split-beam transducer. This transducer will allow for enhanced water column/oceanographic monitoring.
• Calibration of all five EK frequencies. The entire suite of EK split-beam transducers is fully calibrated for 2021 operations.
• Four successful CTD casts. These casts confirmed the functionality of the CTD rosette for the 2021 Technology Demonstration, as well as for all subsequent expeditions.
• Drafts completed for the 2021 EK Calibration Report, 2021 Readiness Report, 2021 Multibeam Calibration Report, the EX-21-01 Mapping Data Report, and four outstanding EK Calibration Reports.
• Three Expedition Features on the NOAA Ocean Exploration website. These features include information on the EM 304, EK 80, and CTD Water Sampling.
• An investigation into potential uses of the Scientific Flow Through system. NOAA Ocean Exploration scoped new potential objectives that would leverage the Scientific Flow Through System on board, including microplastics, eDNA, and pCO2 (partial pressure of carbon dioxide) measurements.
• Successful testing of Seafloor Mapping Cloud Pilot Project. This included stress testing of online cloud resources for bathymetric data processing, Standard Operating Procedures creation, and the training of two Explorers-in-Training for future expeditions.

These achievements would not have been possible without the tireless efforts of the expedition team, consisting of members from NOAA Ocean Exploration and the Global Foundation for Ocean Exploration, as well as the command and crew of NOAA Ship Okeanos Explorer. The excellent teamwork and communication exhibited between the ship’s crew and expedition teams both aboard and on shore contributed immensely to the ultimate successes of this expedition, and is encouraging of another successful year of NOAA Ocean Exploration work aboard NOAA Ship Okeanos Explorer!