Equipment Used: NOAA Ship Okeanos Explorer is equipped with a 26 kilohertz (kHz) Kongsberg EM 304 MKII multibeam sonar. The nominal transmit (TX) alongtrack beamwidth is 0.5°, and the nominal receive (RX) acrosstrack beamwidth is 1.0°. The system generates a 150° beam fan, containing 512 beams with up to 800 soundings per ping cycle when in high-density mode. In waters shallower than approximately 3,300 m the system is able to operate in dual-swath mode, where one nominal ping cycle includes two swaths, resulting in up to 1,600 soundings. Data are recorded using Kongsberg's Seafloor Information System (SIS) software. Collocated to the bathymetric data, bottom backscatter data were collected and stored within the raw files, both as beam-averaged backscatter values, and as full-time series values (snippets) within each beam. During standard data acquisition, the EM 304 multibeam sonar is synchronized with the other active sonars using the Kongsberg Synchronization Unit with the EM 304 multibeam sonar set as the master. Any changes in equipment setup for the year or expedition are detailed in the annual Readiness Report or associated Expedition Report, respectively. For general information about sub-bottom operations, please refer to the NOAA Ocean Exploration Mapping Procedures Manual. Calibrations: At the beginning of each field season, a multibeam geometric calibration (patch test) is conducted to resolve any angular misalignments of the EM 304 multibeam equipment. A patch test is also conducted if any multibeam equipment (e.g., transducers, IMU, antennas) is installed or disturbed. The patch test determines if there are any residual biases or errors in navigation timing, pitch, roll, and heading/yaw (and resolves each bias individually in that order). Whenever possible (and assuming reasonable values), the results of each test are applied in SIS prior to data collection for the following test. Calibration Reports are archived as supplemental documents to the annual Readiness Report throughout the year. A relative backscatter correction was performed in 2021, and the resulting gain values were uploaded to the processing unit. This procedure helps to normalize differences in backscatter values resulting from variable frequencies and pulse durations employed within sectors and among ping modes used during multibeam data acquisition. Acquisition Corrections: Real-time corrections to the data upon acquisition include the continuous application of surface sound speed obtained with a hull-mounted Reson SV-70 probe, and application of water column sound speed profiles obtained with Sippican Deep Blue Expendable Bathythermographs (XBTs) and/or Seabird CTD 9/11. Sound speed profiles are conducted every four hours, or more frequently as dictated by local oceanographic conditions (typically every two hours when operating in more dynamic areas). Reson sound speed values are constantly compared against secondarily derived sound speed values from the ship’s onboard thermosalinograph flow-through system as a quality assurance measure. Roll, pitch, and heave motion corrections are applied in real-time via a POS MV 320 version 5 or a Seapath-380, using Marine Star DGPS correctors. The motion and positioning unit used will be noted in the processing logs. No tidal corrections are applied to the raw or processed data. Multibeam data quality is monitored in real-time by acquisition watchstanders. Ship speed is adjusted to maintain data quality and sounding density as necessary. Line spacing is planned to ensure one-quarter to one-third swath-width overlap between lines, depending on the environmental conditions and impact on the quality of the outer swath regions. Angles are generally left open (70°/70°) during transits to maximize data collection and are adjusted on both the port and starboard sides to ensure the best data quality and coverage. If outer beams are returning obviously spurious soundings (e.g., due to attenuation or low

The 2021 North Atlantic Stepping Stones: New England and Corner Rise Seamounts expedition (EX-21-04) was a combined mapping and remotely operated vehicle (ROV) expedition to the seamounts of the Northwest Atlantic that took place between June 30 and July 29, 2021. Operations during this 30-day at sea expedition included a combination of ROV dives in support of NOAA Ocean Exploration and its partner priorities as well as exploratory mapping operations targeting areas containing no or poor quality modern mapping data. The initial focus was on the U.S. Northeast Seamount and high seas areas, however, during the expedition weather altered the planned transect to outside Bermudan waters where three dives took place before rejoining the planned dive sites exploring a total of 19 seamounts and one canyon (Hydrographer) for water column exploration. During the expedition, 20 Deep Discoverer ROV dives were conducted from 300 m to 4187 m water depth for a total of 154 hours of bottom time, and surveyed using EM 304 multibeam sonar 54,710 square km over 30 days at sea. All data associated with this expedition have been archived and are publicly available through the NOAA Archives.

Equipment Used: NOAA Ship Okeanos Explorer is equipped with a 26 kilohertz (kHz) Kongsberg EM 304 MKII multibeam sonar. The nominal transmit (TX) alongtrack beamwidth is 0.5°, and the nominal receive (RX) acrosstrack beamwidth is 1.0°. The system generates a 150° beam fan, containing 512 beams with up to 800 soundings per ping cycle when in high-density mode. In waters shallower than approximately 3,300 m the system is able to operate in dual-swath mode, where one nominal ping cycle includes two swaths, resulting in up to 1,600 soundings. Data are recorded using Kongsberg's Seafloor Information System (SIS) software. Collocated to the bathymetric data, bottom backscatter data were collected and stored within the raw files, both as beam-averaged backscatter values, and as full-time series values (snippets) within each beam. During standard data acquisition, the EM 304 multibeam sonar is synchronized with the other active sonars using the Kongsberg Synchronization Unit with the EM 304 multibeam sonar set as the master. Any changes in equipment setup for the year or expedition are detailed in the annual Readiness Report or associated Expedition Report, respectively. For general information about sub-bottom operations, please refer to the NOAA Ocean Exploration Mapping Procedures Manual. Calibrations: At the beginning of each field season, a multibeam geometric calibration (patch test) is conducted to resolve any angular misalignments of the EM 304 multibeam equipment. A patch test is also conducted if any multibeam equipment (e.g., transducers, IMU, antennas) is installed or disturbed. The patch test determines if there are any residual biases or errors in navigation timing, pitch, roll, and heading/yaw (and resolves each bias individually in that order). Whenever possible (and assuming reasonable values), the results of each test are applied in SIS prior to data collection for the following test. Calibration Reports are archived as supplemental documents to the annual Readiness Report throughout the year. A relative backscatter correction was performed in 2021, and the resulting gain values were uploaded to the processing unit. This procedure helps to normalize differences in backscatter values resulting from variable frequencies and pulse durations employed within sectors and among ping modes used during multibeam data acquisition. Acquisition Corrections: Real-time corrections to the data upon acquisition include the continuous application of surface sound speed obtained with a hull-mounted Reson SV-70 probe, and application of water column sound speed profiles obtained with Sippican Deep Blue Expendable Bathythermographs (XBTs) and/or Seabird CTD 9/11. Sound speed profiles are conducted every four hours, or more frequently as dictated by local oceanographic conditions (typically every two hours when operating in more dynamic areas). Reson sound speed values are constantly compared against secondarily derived sound speed values from the ship’s onboard thermosalinograph flow-through system as a quality assurance measure. Roll, pitch, and heave motion corrections are applied in real-time via a POS MV 320 version 5 or a Seapath-380, using Marine Star DGPS correctors. The motion and positioning unit used will be noted in the processing logs. No tidal corrections are applied to the raw or processed data. Multibeam data quality is monitored in real-time by acquisition watchstanders. Ship speed is adjusted to maintain data quality and sounding density as necessary. Line spacing is planned to ensure one-quarter to one-third swath-width overlap between lines, depending on the environmental conditions and impact on the quality of the outer swath regions. Angles are generally left open (70°/70°) during transits to maximize data collection and are adjusted on both the port and starboard sides to ensure the best data quality and coverage. If outer beams are returning obviously spurious soundings (e.g., due to attenuation or low

From May 14-27, 2021, NOAA Ocean Exploration led the 2021 Technology Demonstration on NOAA Ship Okeanos Explorer from Cape Canaveral, Florida, to Norfolk, Virginia. The expedition brought together NOAA's Northwest Fisheries Science Center, NASA's Jet Propulsion Laboratory (NASA JPL), the Woods Hole Oceanographic Institution (WHOI), and the Inner Space Center/University of Rhode Island (ISC/URO) to advance new ocean technologies and sampling techniques. The expedition had three overall objectives; field testing and engineering readiness of WHOI/NASA JPL Orpheus autonomous underwater vehicles, piloting environmental DNA (eDNA) collection for NOAA Ocean Exploration and mapping priority deepwater areas offshore the U.S. Southeast, largely focused on the Blake Plateau. During 14 days at sea, 8 AUV deployments were completed between 12 and 866 meters in depth. Over 724 GB of downlooking AUV 4K video were collected. The AUVs surveyed 30 linear kilometers of seafloor and logged over 16 hours of bottom time. The AUVs spent a total of 32 hours 59 minutes in the water, which included autonomous water column exploration. Twelve CTD rosette casts were completed, most simultaneous with AUV operations. Using the Niskin bottles on the CTD rosette, 120 water samples were collected for post-cruise eDNA analysis. Exploration mapping operations included acoustic data collection using the EM 304 MKII multibeam echosounder, Simrad EK60/80 split-beam echosounders, Knudsen sub-bottom profiler and Acoustic Doppler Profilers. 8,703 square kilometers of largely unmapped seafloor were mapped using the EM 304 with 8,519 square kilometers being within the U.S. Exclusive Economic Zone and Territorial Sea deeper than 200 m. All operations and data collected were in U.S. waters.

Equipment Used: NOAA Ship Okeanos Explorer is equipped with a 26 kilohertz (kHz) Kongsberg EM 304 MKII multibeam sonar. The nominal transmit (TX) alongtrack beamwidth is 0.5°, and the nominal receive (RX) acrosstrack beamwidth is 1.0°. The system generates a 150° beam fan, containing 512 beams with up to 800 soundings per ping cycle when in high-density mode. In waters shallower than approximately 3,300 m the system is able to operate in dual-swath mode, where one nominal ping cycle includes two swaths, resulting in up to 1,600 soundings. Data are recorded using Kongsberg's Seafloor Information System (SIS) software. Collocated to the bathymetric data, bottom backscatter data were collected and stored within the raw files, both as beam-averaged backscatter values, and as full-time series values (snippets) within each beam. During standard data acquisition, the EM 304 multibeam sonar is synchronized with the other active sonars using the Kongsberg Synchronization Unit with the EM 304 multibeam sonar set as the master. Any changes in equipment setup for the year or expedition are detailed in the annual Readiness Report or associated Expedition Report, respectively. For general information about sub-bottom operations, please refer to the NOAA Ocean Exploration Mapping Procedures Manual. Calibrations: At the beginning of each field season, a multibeam geometric calibration (patch test) is conducted to resolve any angular misalignments of the EM 304 multibeam equipment. A patch test is also conducted if any multibeam equipment (e.g., transducers, IMU, antennas) is installed or disturbed. The patch test determines if there are any residual biases or errors in navigation timing, pitch, roll, and heading/yaw (and resolves each bias individually in that order). Whenever possible (and assuming reasonable values), the results of each test are applied in SIS prior to data collection for the following test. Calibration Reports are archived as supplemental documents to the annual Readiness Report throughout the year. A relative backscatter correction was performed in 2021, and the resulting gain values were uploaded to the processing unit. This procedure helps to normalize differences in backscatter values resulting from variable frequencies and pulse durations employed within sectors and among ping modes used during multibeam data acquisition. Acquisition Corrections: Real-time corrections to the data upon acquisition include the continuous application of surface sound speed obtained with a hull-mounted Reson SV-70 probe, and application of water column sound speed profiles obtained with Sippican Deep Blue Expendable Bathythermographs (XBTs) and/or Seabird CTD 9/11. Sound speed profiles are conducted every four hours, or more frequently as dictated by local oceanographic conditions (typically every two hours when operating in more dynamic areas). Reson sound speed values are constantly compared against secondarily derived sound speed values from the ship’s onboard thermosalinograph flow-through system as a quality assurance measure. Roll, pitch, and heave motion corrections are applied in real-time via a POS MV 320 version 5 or a Seapath-380, using Marine Star DGPS correctors. The motion and positioning unit used will be noted in the processing logs. No tidal corrections are applied to the raw or processed data. Multibeam data quality is monitored in real-time by acquisition watchstanders. Ship speed is adjusted to maintain data quality and sounding density as necessary. Line spacing is planned to ensure one-quarter to one-third swath-width overlap between lines, depending on the environmental conditions and impact on the quality of the outer swath regions. Angles are generally left open (70°/70°) during transits to maximize data collection and are adjusted on both the port and starboard sides to ensure the best data quality and coverage. If outer beams are returning obviously spurious soundings (e.g., due to attenuation or low

From April 13 - May 4, 2024 (San Francisco, California to Honolulu, Hawai’i), NOAA Ocean Exploration conducted the 2024 Mapping Shakedown + High Seas Mapping expedition to test and calibrate the acoustic mapping and associated systems aboard the NOAAS Okeanos Explorer following a drydock period over the winter or 2023/2024. The primary focus of this expedition was to ensure readiness of all sensors and equipment for the 2024 field season. Shakedown and readiness operations included calibrations of the POS MV and Seapath positioning and attitude systems, geometric calibration of the EM304 MKII multibeam echosounder, multibeam swath accuracy assessment at expected operational depths for this field season, speed-noise tests, and calibrations of each of the EK60/80 split beam sonars.

From September 5 - September 28, 2021, NOAA Ocean Exploration conducted mapping operations on the Blake Plateau within U.S. waters, aiding in closing the gaps within this region. The second of two cruises focused on mapping this region, EX-21-06 collected 25,800 square kilometers of bathymetry and associated water column data, 25,790 square kilometers of which were within the U.S. Exclusive Economic Zone and Territorial Sea deeper than 200 m. The exploratory mapping operations conducted during this cruise will provide initial characterization of the region, as well as data to support further exploration with remotely operated vehicles planned for EX-21-07.

From May 14 - June 7, 2022 (Newport, Rhode Island to St. John's, Newfoundland), NOAA Ocean Exploration conducted mapping operations on the Charlie Gibbs Fracture Zone, aiding in closing bathymetric gaps within this region. EX-22-04 collected 46,250 square kilometers of bathymetry and associated water column data. During mapping operations, NOAA Ocean Exploration simultaneously collected EM 304 multibeam sonar bathymetry observations and Simrad EK60/EK80 split-beam fisheries sonar observations of biologic material in the water column, as well as Knudsen 3260 sub-bottom profiler observations of sub-seafloor geologic structure and sediment. Additionally, a calibration of the EK60/EK80 transducers was completed. The exploratory mapping operations conducted during this cruise will provide initial characterization of the region, as well as data to support further exploration.

From May 5 – 26, 2023 (Seattle, Washington, to Dutch Harbor, Alaska), NOAA Ocean Exploration conducted transit and mapping operations off the coast of Washington State, the Gulf of Alaska, and along the Aleutian Islands. The ship departed from Seattle, Washington. Expedition EX-23-02 collected data supporting the Seascape Alaska initiative and used a small, human portable AUV in partnership with the Defense POW/MIA Accounting Agency (DPAA) to aid in locating an aircraft lost in the Aleutian Islands during World War II. Transit mapping data was collected from Seattle, Washington, across the Gulf of Alaska, and along the northern and southern edges of the Aleutian Islands, extending from approximately Unga Island to Gareloi Island. Primary mapping activities focused on the area connecting the Aleutian Arc and the southern end of Bowers Ridge and the area surrounding Bogoslof Island. The ship returned to port in Dutch Harbor, Alaska. The exploratory mapping operations conducted on this expedition will aid in future characterization of these unexplored areas and help initial characterization in the region.

Between April 14 and May 10, 2021 EX-21-01 performed the sea acceptance testing of the newly installed Kongsberg EM 304 MKII transmit array, conducted mission readiness of the mapping systems through annual testing and calibration, and mapped unexplored areas of the Blake Plateau. In addition to the EM 304 multibeam sonar objectives, EK60/80 split-beam echosounder objectives included acceptance of the newly installed EK80 38 kHz transducer and calibration of each frequency (18, 38, 70, 120, 200 kHz). Other mission readiness objectives included ensuring functionality of all ancillary equipment, including sound speed profiling equipment, updating and refining procedural documents, and defining new procedures for supporting shore-based processing using the Cloud. EX-21-01 collected 22,187 square kilometers of bathymetry and associated water column data, with 18,773 square kilometers being within the U.S. Exclusive Economic Zone and Territorial Sea deeper than 200 m.