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 February 23 - March 3, 2022 (Pascagoula, MS to Key West, FL), NOAA Ocean Exploration conducted a shakedown of the remotely operated vehicle (ROV), video, telepresence, and sampling operations as well as mapping and positioning systems aboard NOAA Ship Okeanos Explorer. The ROV engineers tested and calibrated ROVs Deep Discoverer and Seirios' ROV motor controllers, auto position software, lighting system, hydraulic system, ME-20 low-light camera, high-definition ancillary ROV cameras, sector-scanning sonar, as well as tested remote-piloting capabilities of ROV Deep Discoverer. Shakedown and readiness operations for the EM 304 multibeam sonar included a GNSS Azimuth Measurement Subsystem (GAMS) calibration, Patch Test, speed-noise test, coverage extinction data collection, and integration and testing of the newly installed SeaPath 380-R3. In total, the expedition team conducted 7 ROV dives ranging from 480 to 3,420 m depth and collected 4,930 square kilometers of acoustic data during transits and calibrations. The expedition explored the West Florida Shelf and the Straits of Florida offshore the U.S. southeastern coast. The expedition confirmed the location of a shipwreck target, thought to be a 19th century whaler. Corals and sponges were observed 4 out of the 7 surveyed dive sites, with 3 of the 7 containing high diversities of benthic species. A total of 12 samples were collected: 3 geological, 3 biological, and 6 commensal (not including blank samples).

From July 9-30, 2022 (Norfolk, VA to Horta, Faial, Azores) NOAA Ocean Exploration completed the Voyage to the Ridge 2 expedition (EX-22-05), a combined mapping and remotely operated vehicle (ROV) expedition to the Mid-Atlantic Ridge and Azores Plateau. Operations during this 22-days at sea expedition included the completion of 10 successful ROV exploration dives in the vicinity the Azores and the Mid-Atlantic Ridge north of the Azores. ROV dives were conducted in water depths ranging from 420 m to 3350 m for a total of almost 53 hours of bottom time. EX-22-05 also collected 49,080 square kilometers of seafloor bathymetry and associated water column data using an EM304 multibeam sonar.

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.

From April 4 - 28, 2022, NOAA Ship Okeanos Explorer sailed to support NOAA Ocean Exploration's Puerto Rico Mapping and Deep-Sea Camera expedition (EX-22-03). The ship departed from San Juan, Puerto Rico. The mission objectives were two-fold: seafloor mapping in U.S waters offshore of Puerto Rico and testing deep-sea camera systems developed by the Multidisciplinary Instrumentation in Support of Oceanography (MISO) Facility at the Woods Hole Oceanographic Institution (WHOI) for potential integration into future NOAA Ocean Exploration operations. The primary mapping area of the expedition was the Muertos Trough region and surrounding seamounts in U.S. Caribbean waters around Puerto Rico. In addition, a transit over the 8,000 m deep Puerto Rico Trench was used to test the limits of the new Kongsberg EM 304 MKII multibeam sonar that was installed in 2021. Upon completion of mapping in the priority areas, the expedition focused on testing the integrated deep-sea camera and conductivity, temperature, and depth (CTD) system to support a number of mission objectives through simultaneous imaging and sampling of the water column. The last portion of the expedition consisted of mapping the high seas and offshore waters of the U.S. East Coast while transiting to the final destination of Newport, Rhode Island.

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 August 1 - August 17, 2023 (Unalaska, Alaska to Kodiak, Alaska), NOAA Ocean Exploration completed the expedition Seascape Alaska 4: Gulf of Alaska Mapping (EX2305). Mapping operations during this 17-day expedition aided in closing bathymetric gaps off the coast of the Aleutian Islands and in the Gulf of Alaska. EX2305 collected 23,591 square kilometers of seafloor bathymetry within the U.S. Exclusive Economic Zone deeper than 200 m. 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. A focused survey region targeted seamounts in the Gulf of Alaska. During the expedition, an EK calibration was completed for the 18, 38, 70, 120, and 200 kHz frequency sonars. The exploratory mapping operations conducted during this cruise will provide initial characterization of the region, as well as data to support further exploration. All data associated with this expedition will be archived within 120 days of the end of the expedition and will be publicly available through the NOAA Archives.

The Windows to the Deep 2021: Southeast U.S. ROV and Mapping expedition (EX-21-07) was a combined mapping and remotely operated vehicle (ROV) expedition to the Blake Plateau and Florida Straits that took place between October 26 and November 15, 2021. Operations during this 21-days at sea expedition included a combination of ROV dives in support of NOAA Ocean Exploration and its partner priorities. The primary focus of this expedition was the Blake Plateau, including its escarpment, off the coast of the Southeast U.S., but three dives were also conducted in the western and central Florida Straits due to weather conditions. Overall, 14 dives were completed, including two explorations of the water column, several dives to mound and ridgelike structures likely to be bioherms, two deeper dives to explore the steep Blake Escarpment, and one dive to document a lone sinkhole in the southeast region of the Blake Plateau. ROV dives were conducted from 300 m to 3650 meters water depth for a total of 47 hours of bottom time, and 15,800 square km were mapped using EM 304 multibeam sonar.

From August 15- September 2, 2021, NOAA Ocean Exploration conducted mapping operations on the Blake Plateau within U.S. waters, aiding in closing the gaps within this region. This cruise consisted of a strategic transit from Newport, Rhode Island to the primary working grounds off of the U.S Southeast, aimed at collecting data over previously mapped and potentially new seeps along the edge of the continental shelf. EX-21-05 collected 13,054 square kilometers of bathymetry and associated water column data, 12,989 square kilometers of which were within the U.S. Exclusive Economic Zone and Territorial Sea deeper than 200 m. The cruise concluded in Port Canaveral, FL on September 2, 2021. 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 March 10 - 28, 2021 (Key West, FL to San Juan, Puerto Rico), NOAA Ocean Exploration conducted mapping operations south of Puerto Rico in U.S. waters, aiding in closing bathymetric gaps within this region. EX-22-02 collected 18,850 square kilometers of bathymetry and associated water column data, 18,033 square kilometers of which were within the U.S. Exclusive Economic Zone and Territorial Sea deeper than 200 m. 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. A single CTD cast during the expedition validated deep deployment capabilities in preparation for planned CTD operations on EX-22-03. The exploratory mapping operations conducted during this cruise will provide initial characterization of the region, as well as data to support further exploration.