Observation of a remote island volcano by an unmanned helicopter taking off from a research vessel and operated remotely via satellite communications (flash report)

1. Key Points

• The first successful observation of a remote island volcano by an unmanned helicopter (UAV) operated remotely via satellite communications, landing and taking off from a research vessel.

• The long range of the unmanned helicopter and the use of satellite communications enabled wide-area observations on a remote island volcano that is difficult to approach.

• Our results demonstrated the potential to efficiently conduct a variety of surveys by combining small-medium sized UAVs with the unmanned helicopter.

2. Overview

Researchers from JAMSTEC (Kenta Yoshida, Noriko Tada, & Yuya Akamatsu and Nagoya University (Hiroshi Ichihara & Manaka Kuroda) in collaboration with the JDRONE Inc. and Tierra Tecnica Inc. conducted an aerial geophysical survey of an uninhibited island volcano using an unmanned helicopter (a kind of unmanned aerial vehicle, UAV) operated remotely via satellite communication, landing and taking off from a research vessel (Fig. 1). During a research cruise, an unmanned helicopter with satellite communications was launched from the deck of the R/V Kaimei to demonstrate that it is possible to safely and efficiently observe remote island volcanoes, which has been difficult in the past.

UAVs have been spread rapidly in recent years; however, major UAVs are battery powered and have short range time (~20 min.) and can only fly within the direct radio range (~2-4 km). In contrast, the unmanned helicopter with satellite communications is engine-driven and have a long-range time (~90 min.). After takeoff, the helicopter switches to remote control from a base station on land, making it possible to observe islands at a distance from the mother ship. In this research cruise, the helicopter was remotely piloted from Minamisoma, Fukushima Prefecture, and successfully mapped the magnetic anomaly over an area of approximately 4 × 6 km using a geomagnetic sensor, targeting Nishinoshima Island in the Ogasawara (Bonin) Islands, which has shown intermittent eruptions. This result is difficult to achieve using major battery-powered UAVs, and is expected to be applied to remote island volcano observations employing other observation equipment in the future.

This research is supported by ERCA Environment Research and Technology Development Fund (JPMEERF20244002) and JSPS KAKENHI (JP24K00743).

Figure 1. Schematic image of the survey. During the research cruise using the R/V Kaimei, the observation was performed using an unmanned helicopter taking off from the deck of the ship and operated remotely via satellite communications.

3. Results

Recently, frequent volcanic activities have been observed in the Izu-Ogasawara (Bonin) arc, including the intermittent eruptions of Nishinoshima from 2013 and a large eruption and corresponding pumice rafting of Fukutoku-Oka-no-Ba in 2021, which can produce disaster-like phenomena even for distant places. Volcanic islands and submarine volcanoes in offshore far from inhabited areas have difficulty for direct and continuous observations. Therefore, observation of the proximal area using research vessels and UAVs is the primary ways of survey.

Nishinoshima is a currently-active volcanic island showing intermittent activities since 2013. In 2020, Nishinoshima showed abrupt change in the eruption style, showing violent Strombolian to enlarge its size from ~1.8 km to ~2.5 km squares. We previously performed tephra and water sampling on and around the island along with the seafloor survey using research vessels. In addition, we employed a middle-sized UAV with a geomagnetic sensor, flying over the island repeatedly to obtain a geomagnetic intensity map (aerial geomagnetic survey), to investigate the internal structure of the volcano. However, after the 2020 eruption, the enlarged island has difficulty to perform aerial geomagnetic survey using a battery-powered UAV that can fly only ~20 minutes.

To overcome this problem, we employed an unmanned helicopter (large UAV) that is engine-driven and have a long range time (~90 min.) and can be operated via satellite communications. The candidate helicopter “YAMAHA FAZER R G2” can take off from the deck of the R/V Kaimei and can be operated from the operating base on land (Minamisoma, Fukushima Prefecture) via satellite communications (Fig. 2).

Figure 2. (upper) Research facilities employed in this study, R/V Kaimei (upper left) and the helicopter FAZER R G2 (upper right). (lower) The helicopter is taking off from the deck of the ship, flying to the island for the geomagnetic survey. A geomagnetic sensor is towed from the helicopter by a ^~5m cable.

The research cruise KM25-02 Leg2 was undertaken in March 2025. The geomagnetic survey was performed by onboard team including helicopter pilots and geophysists and on-land helicopter operators. The onboard and on-land teams communicated using a web meeting via satellite-based internet. The helicopter takeoffs and landings were done by direct piloting by onboard pilots, while it switched to remote control from Minamisoma after the helicopter rose to ~ 200m height.

Geomagnetic survey was performed using a geomagnetic sensor towed by a ~5m cable from the helicopter. The geomagnetic field normally points in a north-south direction, but there may be localized areas where the direction and intensity of the magnetic field differs due to the magnetic properties of the underground rocks and magma (magnetic anomalies). Such magnetic anomalies are clue to investigate the size and shape of the magma reservoir under the volcano.

During the cruise, we performed 8 flights in 3 days to obtain the geomagnetic map of the whole area of Nishinoshima Island (Fig. 3). During the helicopter’s 90-minute flight, small and middle-sized UAVs were operated to the coastal area, where they simultaneously conducted other tasks that are conventionally performed for volcano observation, such as topographic surveying and water sampling (Fig. 4).

The obtained geomagnetic data are suitable for detailed analysis. We will apply the method employed in the previous study ^Ref.1 to investigate the change in the internal structure of the Nishinoshima volcano after the explosive eruption in 2020.

This observation demonstrated that a combination of wide-area observations by unmanned helicopters and conventional UAV observations can be used to conduct efficient observations on active volcanic islands.

Figure 3. Geomagnetic mapping result of this survey. A total of 8 flights in 3 days achieved a complete mapping of Nishinoshima Island with high quality.

Figure 4. A middle-sized UAV used for water sampling, taking off during the 90-minute flight of the helicopter. The discolored water occurring near the coasts was sampled.