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.

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.

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.

This Remotely Operated Vehicle (ROV) shakedown expedition aboard NOAA Ship Okeanos Explorer began in Norfolk, Virginia on June 13, 2021 and concluded on June 28, 2021 in Newport, Rhode Island. This was the first time the ROVs Deep Discoverer and Seirios were mobilized and used for ROV dives since the extensive 2021 winter dry dock repair period. While underway, 24?hour operations focused on preparing remotely operated vehicle (ROV) systems for the remainder of 2021 expeditions. Extensive testing, calibration, and troubleshooting was completed for new ROV motors, motor controllers, cameras, lighting, hydraulic systems, and a navigational sonar during 11 ROV dives. The first five dives progressively got to deeper depths ranging from 670 m to 4370 m with the primary objective of new equipment integration and personnel training. The following five dives were conducted on Caryn Seamount, and the mid-Atlantic canyons Toms, Hudson (twice), and Uchupi. The last dive of the expedition was on a recently discovered sonar anomaly that turned out to be a World War II era submarine, the Humaita (ex-USS Muskallunge). Five biological and three geological samples were collected for later analyses from Caryn Seamount and the mid-Atlantic canyons. Mapping operations during the expedition included continued calibrating and troubleshooting of the ship's new EM304 multibeam sonar and transducer array. Additional mapping operations included improving multibeam bathymetry in previously mapped areas, sub-bottom sonar surveys conducted on the Currituck landslide feature off of North Carolina, EK60 water column sonar survey of the diurnal migration above Hudson Canyon, and searching for underwater cultural heritage sites by observing sonar depth and backscatter anomalies.

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.

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.

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.

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 October 16-November 3, 2022 (San Diego, California to Newport, Oregon), NOAA Ocean Exploration conducted mapping operations off the coast of California and Oregon in U.S. waters, aiding in closing bathymetric gaps within this region. Expedition EX-22-08 collected 32,416 square kilometers of bathymetry and associated water column data, 22,313 square kilometers of which were within the U.S. Exclusive Economic Zone and Territorial Sea deeper than 200 m, while 10,104 square kilometers were collected in international waters. 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 detailed sub-bottom survey targeted previously-identified sponge reefs in the Channel Islands National Marine Sanctuary. The exploratory mapping operations conducted during this cruise will provide initial characterization of the region, as well as data to support further exploration.

From August 6 - September 2, 2022 (Horta, Faial, Azores to San Juan, Puerto Rico) NOAA Ocean Exploration completed the Voyage to the Ridge 3 expedition (EX-22-06), a combined mapping and remotely operated vehicle (ROV) expedition to the Mid-Atlantic Ridge and Azores Plateau, Mid-Atlantic Ridge, and U.S. waters in the vicinity of Puerto Rico and the U.S. Virgin Islands. Operations during this 28-day expedition included the completion of 9 successful ROV exploration dives in the vicinity of the Azores, the Mid-Atlantic Ridge south of the Azores, and Puerto Rico. ROV dives were conducted in water depths ranging from 250 m to 6000 m for a total of 41 hours of bottom time. EX-22-06 also collected 56,769 square kilometers of seafloor bathymetry and associated water column data using an EM304 multibeam sonar. All data associated with this expedition have been archived and are publicly available through the NOAA Archives.