AN/SPY-6(V)4: The U.S. Navy’s New Radar Era at Sea

On August 26, 2025, the U.S. Navy, together with Raytheon (RTX), completed the first open-water trials of the AN/SPY-6(V)4 radar at the Pacific Missile Range Facility in Hawaii. This marked not only the debut of the Navy’s most advanced radar outside laboratory settings but also the beginning of a transformative modernization program that will reshape how American destroyers perceive and fight in the 21st-century battlespace.

Unlike its predecessor SPY-1, which defined the Aegis era since the 1980s, SPY-6 is designed for a battlespace dominated by hypersonic glide vehicles, stealth aircraft, ballistic salvos, drone swarms, and electronic warfare saturation.

The test was more than a milestone—it was a message: the Navy is preparing its fleet to survive the missile age of China and Russia.

From SPY-1 to SPY-6: A Legacy of Aegis Radars

When the Aegis Combat System entered service in the early 1980s, the SPY-1 phased-array radar was revolutionary. It provided simultaneous air and missile tracking, enabled Standard Missile intercepts, and gave Arleigh Burke destroyers the situational awareness edge that made them the backbone of U.S. naval power.

But after four decades, SPY-1 is nearing obsolescence. Its analog electronics, limited processing power, and reduced ability to counter low-observable and hypersonic threats leave the fleet vulnerable. Even with upgrades like the SPY-1D(V), it cannot scale to modern threat density.

Enter the SPY-6 family—a modular, scalable radar designed for all Navy combatants: Flight III destroyers, carriers, amphibs, and now even Flight IIA destroyers through the DDG MOD 2.0 program.

Anatomy of the SPY-6(V)4

The (V)4 variant is tailored specifically for Arleigh Burke Flight IIA destroyers, which were originally built with SPY-1D(V) radars. Instead of tearing out the ship’s design, the Navy opted for a 24-RMA (Radar Modular Assembly) configuration.

Key Features

• Architecture: Four fixed AESA panels, each composed of 24 RMAs.

• Technology: Gallium Nitride (GaN) semiconductors — higher efficiency, lower heat signature, 35× more sensitivity than SPY-1.

• Coverage: 360° simultaneous tracking of air, surface, and ballistic threats.

• Throughput: Can handle over 30 times more targets than SPY-1.

• Scalability: Shares architecture with SPY-6(V)1 (37 RMAs on Flight III destroyers) and SPY-6(V)2/3 for carriers and amphibs.

• Integration: Directly tied to Aegis Combat System Baseline 10, allowing seamless SM-2/SM-6/SM-3 intercepts and future hypersonic defense.

This modularity means RMAs can be added or reduced depending on ship class—effectively a “Lego radar” that standardizes training and logistics across the fleet.

First Trials: Hawaii 2025

The August 2025 tests marked the first maritime validation of SPY-6(V)4.

• Conducted at the Pacific Missile Range Facility (PMRF) in Hawaii.

• Evaluated detection against air and surface threats, including drones and simulated cruise missiles.

• Focus: tracking precision, target discrimination, resistance to clutter and jamming.

According to Navy officials, the trials validated lab predictions and delivered the first operational datasets for refining software algorithms. The radar successfully demonstrated its ability to operate in the electromagnetic environment of the open ocean—something lab tests cannot fully replicate.

The Path to the Fleet: DDG MOD 2.0

The Navy’s DDG MOD 2.0 modernization program will retrofit 12 Flight IIA destroyers with SPY-6(V)4 between 2026 and the mid-2030s.

• First ship: USS Pinckney (DDG-91), entering modernization in 2026 and rejoining the fleet by 2028.

• Scope: Radar upgrade, combat system baseline 10, power/cooling adjustments, and full integration with Aegis.

• Budget: Estimated at $17 billion for the full SPY-6 rollout across platforms, making it one of the Navy’s most significant sensor investments.

Comparing SPY-6 with Rivals

SPY-6 vs. SPY-1

• Power: 35× greater sensitivity.

• Targets: 30× more simultaneous tracks.

• Reliability: GaN vs. outdated analog SPY-1 tech.

SPY-6 vs. European Radars

• Thales SMART-L MM/N (Netherlands): Excellent for ballistic missile defense, but less scalable.

• Leonardo Kronos (Italy): Agile AESA, but smaller coverage footprint.

• Japan’s FCS-3A: Modern AESA, but optimized for regional threats, not global fleet operations.

SPY-6’s modularity and U.S. Navy fleet-wide integration give it unmatched economies of scale and adaptability.

Strategic Context: Countering China and Russia

The rollout of SPY-6(V)4 is not occurring in a vacuum—it is a direct response to evolving threats:

• China: Development of DF-21D and DF-26 anti-ship ballistic missiles, plus YJ-series hypersonic anti-ship weapons.

• Russia: Deployment of Tsirkon hypersonic missiles and massed Kalibr cruise missile salvos from subs and frigates.

In such environments, a radar that can:

1. Detect low-observable threats,

2. Track hypersonics in glide phase,

3. Manage saturation attacks from swarms,

…is no longer a luxury but a necessity.

SPY-6 equips even older destroyers with these capabilities, ensuring the fleet maintains numerical and qualitative dominance in contested seas like the South China Sea and Baltic.

Critical Challenges

While SPY-6(V)4 is a leap forward, challenges remain:

• Power and Cooling: Flight IIA destroyers were not designed for high-demand GaN radars. Extensive modifications are required.

• Integration Delays: Software integration with Aegis Baseline 10 is complex; timelines could slip.

• Budgetary Pressure: Congress faces competing priorities (Columbia-class subs, next-gen fighters). Sustaining radar funding will be a political battle.

• Operational Validation: Lab and trial results are promising, but true test will be live-fire intercepts against fast, maneuvering hypersonics.

Conclusion: A Sea Change in Naval Sensing

The AN/SPY-6(V)4 is more than an upgrade—it is a survival system for the missile age. By extending next-gen radar capability to legacy destroyers, the Navy ensures that the entire fleet—not just new-build ships—can fight in tomorrow’s battlespace.

With its modular design, unmatched sensitivity, and integration into the Aegis ecosystem, SPY-6 is set to become the defining naval radar of the 21st century. Yet, its success will depend on funding stability, technical integration, and the ability to adapt as threats evolve.

If trials continue to deliver, by the early 2030s, the U.S. Navy will operate the most advanced fleet-wide radar network in the world—a critical edge in an era of hypersonics and great power competition.