US nears IMS completion with Antarctic infrasound station

With the successful installation of infrasound station IS54 at Palmer Station in February, the United States has entered the final phase of completing its segment of the International Monitoring System (IMS), pending certification. This milestone marks the culmination of decades of planning and coordination, extending the global verification regime to one of the most remote and demanding environments on Earth. 

Located on Anvers Island in the Antarctic Peninsula, IS54 is the last of four infrasound stations designated for Antarctica under the Treaty. Together with radionuclide station RN73 and auxiliary seismic station AS106 at Palmer Station, it strengthens the Comprehensive Nuclear-Test-Ban Treaty Organization’s (CTBTO) ability to detect nuclear weapon test explosions. 

The installation also reflects a broader achievement. Antarctica, often described as the coldest, driest, and windiest continent, presents unique operational challenges. Establishing and sustaining monitoring stations in such conditions requires both technical precision and logistical ingenuity. 

Getting the equipment to Palmer Station required a different approach. The project relied on a 24-metre sailing vessel, the Pelagic 77 Amundsen. It was the first time this method has been used for a CTBTO station installation. 

Initial transport began in January, when engineers from the Wilson Alaska Technical Center (WATC) at the University of Alaska Fairbanks, responsible for operating IS54, coordinated the delivery of equipment to Palmer Station. The equipment was shipped aboard the support vessel M/V Sola. 

“Transporting two 20-foot containers of 30,000 pounds of break-bulk cargo from the Northern Hemisphere to Antarctica come with their challenges. We needed a boat crew willing to help move container loads of scientific supplies, and both Sola and Amundsen crews proved their mettle in spades,” said D’Aoust. 

Following the delivery, the engineers regrouped at King George Island before returning north to Ushuaia, Argentina, where they joined the wider installation team for the next phase of the mission. 

The second phase began with a southbound voyage from Ushuaia aboard the Amundsen. The 10-person team navigated the Beagle Channel, rounded Cape Horn, and entered the Drake Passage, a stretch of water known for its rapidly changing weather and demanding sea conditions. 

For many of the installation team, the journey was their first experience at sea. Under the guidance of expedition leader Skip Novak and his experienced crew, team members took on practical roles during the crossing, from handling sails to standing watch. 

Crew member Kate Schnippering described the realities of the passage.  

Upon arrival at Palmer Station, the Amundsen was moored in Hero Inlet, a narrow channel adjacent to the base. For the next 20 days, the vessel served as both transport and accommodation for the team. 

Infrasound monitoring is one of four technologies used by the IMS, alongside seismic, hydroacoustic, and radionuclide monitoring. Together, these technologies allow analysts to distinguish between nuclear test explosions and other events such as earthquakes and tsunamis. 

Data from IS54 will support the verification regime. It may also contribute to civil and scientific research, including studies of atmospheric dynamics, glacial activity, and ocean-atmosphere interactions. 

Following this installation, IS54 began transmitting data to the International Data Centre (IDC) in Vienna via the Central Recording Facility at Palmer Station. The successful transmission marked the operational readiness of the station, nearly three decades after its coordinates were first defined. 

With the installation complete, the team began the return journey. Sailing north through the Gerlache Strait and towards the South Shetland Islands, they encountered unexpectedly calm conditions in the Drake Passage, often referred to as the “Drake Lake” when seas are unusually still. 

The contrast with the southbound journey provided a fitting conclusion to a demanding mission. 

The United States currently operates 38 certified IMS facilities. IS54 will be the 39th and final addition to the US segment, the largest part of a global network that will ultimately include 337 facilities. 

With IS54 now operational, the monitoring reach of the system extends further into one of the least accessible regions on the planet, reinforcing the CTBTO’s mission to uphold the global ban on nuclear testing.  

This milestone was made possible with support from the United States, including the Defense Threat Reduction Agency and the University of Alaska Fairbanks.