On May 28, 2020, four uncrewed vessels departed Alameda, California, to begin their transit across the Pacific Ocean, through Unimak Pass, across the Bering Sea, and into the Arctic. These small, uncrewed vessels, powered only by wind and sun, arrived at Point Hope, Alaska, in early August to start an ambitious project acquiring new depth data along the 20 and 50 meter depth contours from Point Hope to the Canadian border. This was the start of a challenging Arctic project that would contend with weather, sea ice, and equipment failures, all while avoiding potential conflicts with indigenous subsistence hunting.
“This was a very unique hydrographic survey mission and I am excited about the role uncrewed systems will play in Arctic seabed mapping as well as nautical chart updates,” said Rear Admiral Shepard M. Smith, director of NOAA’s Office of Coast Survey. “The Arctic region is an unpredictable place and each mission allows us to improve upon our technology and processes to more efficiently and effectively map the seafloor.”
With COVID-19 causing operational limitations for crewed vessels, Coast Survey leveraged uncrewed capabilities to continue surveying, in line with NOAA’s Uncrewed Systems (UxS) Strategy. Working through Coast Survey’s contract partner, TerraSond, Saildrone’s 23-foot uncrewed sailing vessels were selected based on their operational capabilities and nearly silent operation. These vessels rely exclusively on wind power for propulsion, and solar energy to power electronics and sensors. For this project, the saildrones were configured with a low power single beam echo sounder (235 kHz), along with a suite of meteorological and oceanographic sensors. This configuration provided critical depth information for Coast Survey, while also providing a wealth of environmental data for NOAA and the greater scientific community.
“For TerraSond, the choice to use saildrones to complete this mission was obvious,” said Andrew Orthmann, TerraSond Charting Program Manager. “Saildrone has developed a highly refined autonomous sailing vessel with nearly unlimited endurance. This platform allows sensors to be deployed into the arctic in a way not easily achieved by other strategies.”
After safely transiting the nearly 3,000 nautical miles to the Arctic, the saildrones started survey operations on August 2 along the 20 and 50 meter contours. The transit had taken a toll however, with one of the four saildrones experiencing a sonar failure en route. While the other three saildrones started surveying, this saildrone became a “mobile weather buoy,” recording weather data in a small area between Cape Lisburne and Point Lay. Given the paucity of observational data in the Arctic, this provided an opportunity to collect valuable data for weather models.
In early September, while the saildrones were surveying north of Utqiagvik, the project team learned subsistence hunting along the North Slope was starting. This was weeks ahead of the traditional start date, and the presence of the saildrones was perceived as a risk to the subsistence hunts critical to Utqiagvik and indigenous communities along the North Slope. After pausing operations and sailing the saildrones away from Utqiagvik, Coast Survey collaborated with the Alaska Eskimo Whaling Commission (AEWC) to develop an operational plan that mitigated conflicts with subsistence hunters while still achieving Coast Survey’s project objectives.
“Coast Survey is committed to a long and collaborative relationship with all the coastal communities across the Arctic and it is our goal to ensure there was no interference in the traditional hunts,” said Capt. Rick Brennan, chief of Coast Survey’s Hydrographic Surveys Division. “Since last year’s hunt marked a historic low for these communities, our efforts this year were even more critical to ensure our operations did not affect whale migration patterns and further disrupt any subsistence activities.”
With the plan to stay clear of subsistence communities en route to the Canadian border, sea ice conditions became a primary concern, particularly near the community of Kaktovik. Daily sea ice condition reports, provided by the U.S. National Ice Center, conveyed critical information regarding the ice edge’s location, along with forecasted direction and speed of migration. Through these daily reports, the saildrones’ path could be updated to ensure they would not be trapped by ice as they avoided the subsistence areas.
Upon reaching the Canadian border on September 5, the saildrones resumed survey operations along the 20 and 50 meter contours as they started their 800 nautical mile return journey back to Point Hope. Mindful of the subsistence hunting still taking place in the communities of Kaktovik, Nuiqsit, Utqiagvik, and Wainwright, the saildrones continued to sail around these communities to avoid the potential of influencing the hunt.
Having successfully managed weather, subsistence hunting, and sea ice, the next challenge for the project was diminishing daylight. By September 17, each day had nine fewer minutes of daylight than the day before, raising concerns about the saildrones’ power budget. As the saildrones’ electronics are solar powered, less daylight meant solar panels could no longer keep up with power demand, placing a growing burden on the onboard batteries. The engineering team worked hard to maximize the power budget and resulting survey time, but by September 23 there was no longer sufficient light and Arctic survey operations concluded.
At the time this article was published, the saildrones were acquiring additional bathymetry in Norton Sound before starting the 3,000 nautical mile journey back home to Alameda, California. While the Arctic took its toll with all but one of the saildrones suffering some level of equipment failure, the project was a resounding success. In the midst of a pandemic, Coast Survey was able to acquire more than 4,300 nautical miles of new bathymetry in an incredibly challenging region. During the project Coast Survey also strengthened relationships with indigenous communities along the North Slope, and the entire project team gained significant experience operating in the short Arctic summer. All knowledge that will pay dividends for future projects in the region, particularly as Coast Survey looks to contribute to the objectives outlined in the National Strategy for Mapping, Exploring, and Characterizing the U.S. Exclusive Economic Zone.
Once the saildrones safely reach Alameda, the data will be processed by TerraSond and delivered to NOAA. Following quality control processing, the acquired bathymetry will update nautical charts across the Arctic. All data acquired as part of the contract will be made publicly available, and is suitable for use in other scientific efforts such as coastal modeling, weather forecasting, and various other Arctic research projects.