Japan completes first SPY-7 radar detection trials to track multiple missile threats on ASEV destroyers.

Japan’s Ministry of Defense has completed the first SPY-7 radar detection trials for its Aegis System Equipped Vessel (ASEV) program, validating multi-target tracking capability against simulated missile threats in the United States.

Conducted with Lockheed Martin and U.S. partners, the tests confirmed the radar’s ability to detect, classify, and track complex ballistic targets, strengthening Japan’s future sea-based missile defense capacity. The trials, involving SPY-7 integrated with the Aegis combat system in an operational configuration, demonstrated Japan’s progress toward deployable 360-degree ballistic missile defense, directly enhancing readiness and deterrence against regional missile threats through improved tracking accuracy and engagement timelines.

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The two ASEV vessels are expected to rank among the largest surface combatants, with an overall length of about 190 meters, a beam of 25 meters, and a full-load displacement possibly exceeding 16,000 tons, surpassing the U.S. Navy’s Arleigh Burke Flight III destroyers. (Picture sources: Army Recognition and Missile Defense Agency)

On March 20, 2026, Japan’s Ministry of Defense announced that the first target detection trials for the Japanese Aegis System Equipped Vessel (ASEV) were completed in the United States on March 17 and 19. The trials took place at a dedicated facility in Moorestown, New Jersey, using targets launched from controlled test infrastructure and involving coordination with the Missile Defense Agency, Lockheed Martin, and support from the U.S. Navy. The SPY-7 radar was operated in conjunction with the Aegis combat system in a configuration representative of the final ship installation, allowing evaluation across the full sequence of search, detection, identification, tracking, and target management.

The exercise focused on system functionality rather than interception, with simulated engagements conducted after target tracking. Data collection objectives were met in both test events, confirming the system operation under controlled but realistic conditions. The results will undergo detailed analysis before further validation phases, while land-based integration testing is scheduled to continue until July 2026. The tested hardware is now planned for transfer to Japan for installation aboard the first ASEV cruiser. The SPY-7 radar is based on an active electronically scanned array (AESA) architecture derived from the Long Range Discrimination Radar, with a digital, software-defined structure that allows adaptation to evolving threat profiles without major hardware modification.

It is designed to detect and track ballistic missiles and advanced air threats at extended ranges, with the capacity to discriminate between multiple objects within complex trajectories, including clutter and decoys. During the March tests, the SPY-7 demonstrated simultaneous tracking and classification functions, which are critical for ballistic missile defense scenarios involving saturation or multi-axis attacks. The system operates continuously without requiring shutdown for maintenance, supporting sustained readiness during extended deployments. Its integration with the Aegis combat system allows direct linkage between sensor data and interceptor guidance, reducing engagement timelines. The radar is also designed for interoperability with other sensors and networks, enabling coordinated defense operations.

These features permit the engagement of multiple targets in parallel while maintaining tracking accuracy. A key aspect of the recent trials was the use of four fixed radar faces, each approximately 4.3 meters in height, arranged to provide full 360-degree coverage without mechanical rotation. Earlier evaluations used a single face, but the four-face configuration reflects the operational layout planned for the ASEV, enabling continuous tracking across all azimuths. This allows the system to maintain persistent surveillance and reduces blind spots, which is essential for detecting high-speed ballistic targets with limited warning times. The radar’s processing capability enables rapid classification of targets, distinguishing between real threats and decoys based on trajectory and signature.

Its scalable design allows deployment across different ship classes or land-based systems with varying power and size requirements. The system is capable of supporting missions beyond ballistic missile defense, including air defense and tracking of hypersonic glide vehicles. The Japanese Aegis System Equipped Vessel (ASEV) program was initiated as a replacement for the canceled Aegis Ashore system, shifting ballistic missile defense capability from fixed land sites to sea-based assets capable of repositioning. Construction began in fiscal year 2024, with two ballistic missile defense (BMD) cruisers planned, the first scheduled for commissioning by the end of fiscal year 2027 and the second by the end of fiscal year 2028.

The lead ship was laid down on July 18, 2025, at Mitsubishi Heavy Industries’ Nagasaki shipyard, while the second is under construction at Japan Marine United’s Yokohama facility. The ASEV program is structured to provide continuous ballistic missile defense coverage through rotational deployment, although a two-ship fleet limits sustained presence due to maintenance cycles. The ships are intended to operate primarily in areas such as the Sea of Japan, where missile trajectories from regional actors (mainly North Korea and China) are most relevant. This operational concept reduces reliance on land-based systems while maintaining coverage of the national territory. The ASEV vessels are integrated into a broader missile defense architecture that includes existing Aegis destroyers. 

In terms of physical characteristics, the ASEV cruisers will possess a length of 190 meters, a beam of 25 meters, and a standard displacement of about 12,000 tons, with estimates placing full-load displacement closer to or above 16,000 tons. This makes them significantly larger than current Japanese destroyers, such as the Maya- and Atago-class, and also larger than the U.S. Navy’s Arleigh Burke Flight III-class destroyers by a factor of about 1.7 in overall size. The increased dimensions are intended to improve stability in rough seas, ensuring consistent radar performance and reducing motion effects on sensor accuracy during ballistic missile tracking operations.

Some comparisons indicate that their size could exceed that of modern large destroyers such as the U.S. Navy’s Zumwalt-class and China’s Type 055 Renhai-class, though still below the scale of vessels like Russia’s Kirov-class battlecruisers. The ASEV's hull design, notably, prioritizes endurance and operational stability over maneuverability. Propulsion is expected to combine gas turbines and electric drive elements, with Rolls-Royce MT30 turbines providing primary power. Maximum speed is projected to exceed 30 knots. The armament configuration centers on a Mark 41 vertical launching system with 128 cells, allowing deployment of multiple missile types for layered defense and strike missions.

Planned interceptors include the SM-3 Block IIA for exo-atmospheric ballistic missile interception and the SM-6 for terminal-phase defense and engagement of aerodynamic targets. The ships are also expected to carry Tomahawk cruise missiles for long-range strike capability and upgraded Type 12 anti-ship missiles with extended range for both maritime and land targets. Additional systems include close-in weapon systems, electronic warfare suites, and decoy launchers for self-defense against incoming threats. The combination of these weapons enables engagement across different phases of missile trajectories and against multiple threat types.

Cooperative engagement capability and engage-on-remote functions are expected to be integrated, allowing the ships to operate within networked defense environments. Beyond weapons and sensors, the two ASEV ships will incorporate integrated mast structures designed to reduce radar cross-section while housing communication and data link systems, including tactical air navigation and secure communications. Aviation facilities include a flight deck and hangar capable of supporting SH-60 series helicopters, enabling anti-submarine warfare and surveillance operations. Crew complement is estimated at about 240 personnel, with design features aimed at supporting long-duration deployments and improving onboard living conditions.

The propulsion system is configured to balance fuel efficiency and power generation, supporting both propulsion and high-energy sensor requirements. The ships are designed with expansion capacity to integrate future systems, including interceptors for hypersonic threats and potential directed energy systems. Their primary mission remains ballistic missile defense, but their configuration allows for secondary roles in air defense and maritime security. The total estimated cost for the two Aegis System Equipped Vessels is currently about 1 trillion yen, which corresponds to roughly $7.1 billion for the program as a whole.

Written by Jérôme Brahy

Jérôme Brahy is a defense analyst and documentalist at Army Recognition. He specializes in naval modernization, aviation, drones, armored vehicles, and artillery, with a focus on strategic developments in the United States, China, Ukraine, Russia, Türkiye, and Belgium. His analyses go beyond the facts, providing context, identifying key actors, and explaining why defense news matters on a global scale.