AN/SPY-1 Radar

- , December 2018

Quick Facts

Mobility Sea-based is highly mobile; land-based has low mobility
Role Primary radar for Aegis BMD
Deployment Deployed on all 85 U.S. Navy vessels equipped with the Aegis Combat System (including all 38 Aegis BMD-capable vessels); deployed at Aegis Ashore sites in Romania and Kauai, Hawaii.
Frequency S-Band
Range Up to 310 km (estimated)
Producer Lockheed Martin


Army/Navy Joint Electronics Type Designation System/AN/SPY-1 Radar is critical for the U.S. Navy’s aerial radar infrastructure and is a key component of Aegis Ballistic Missile Defense System at sea and on land. U.S. Navy cruisers and destroyers employ SPY-1—in addition to a number of foreign vessels—for Aegis Sea-Based BMD, while on land, the radar system is utilized by Aegis Ashore missile defense sites. Developed by Lockheed Martin, SPY-1 radar was originally designed as an air defense system, but has been upgraded to include a ballistic missile defense (BMD) capability. SPY-1’s passive electronic scanning system is computer controlled, using four complementary antennas in order to provide full 360 degree coverage. It operates in S-band and is a multi-function phased-array radar capable of search, automatic detection, transition to track, tracking of air and surface targets, and missile engagement support.

The SPY-1 can maintain continuous radar surveillance while automatically tracking more than 100 targets at one time. Public numerical figures on the SPY-1 detection range claim that it can detect a golf ball-sized target at ranges in excess of 165 km. When applied to a ballistic missile-sized target, the SPY-1 radar is estimated to have a range of 310 km. The system is designed for blue water and littoral operations however SPY-1 configuration must be modified to look above the terrain to avoid causing excessive false targets from land clutter. Configuration changes to mitigate this technical issue have made it more difficult for AN/SPY-1 to identify and track low and fast targets.

Regional Defense—Engagement Capability Aegis BMD systems are capable of detecting, tracking, targeting, and intercepting cruise and ballistic missile targets. After detecting and identifying a regional missile threat, Aegis BMD can engage and intercept the target using Standard Missile variants guided by tracking information provided by SPY-1. Aegis BMD-equipped cruisers and destroyers are being equipped with the capability to intercept short- and medium-range ballistic missiles as quickly as 10 seconds after the radar “sees” the missile’s movement.

Homeland Defense—Long-Range Surveillance and Tracking Aegis Destroyers on BMD patrol detect and track Intercontinental Ballistic Missiles with SPY-1, reporting tracking data to the Ballistic Missile Defense System (BMDS). The BMDS shares tracking data to cue other missile defense sensors and provides fire control data to Ground-based Mid-course Defense (GMD) interceptors located at Fort Greeley, Alaska and Vandenberg Air Force Base, California. To date, twenty-one Aegis Cruisers and Destroyers have been upgraded with the Long-Range Surveillance and Tracking capability. At-sea tracking events and flight tests have verified the capability to track Intercontinental Ballistic Missiles and demonstrated the connectivity and reliability of long-haul transmission of tracking data (across nine time zones), which is necessary to support missile defense situational awareness, target acquisition, and engagements.

Deployment Variants of the AN/SPY-1 radar are employed by all Aegis BMD systems, both on land—with Aegis Ashore—and at sea—on Ticonderoga (CG-47) Class Aegis Cruisers and Arleigh Burke (DDG-51) Class Aegis Destroyers. As of December 2018, there are 38 Aegis BMD-capable combatants in the U.S. Navy, 5 cruisers (CGs) and 33 destroyers (DDGs). Of the 38 ships, 20 are assigned to the Pacific Fleet and 18 to the Atlantic Fleet. U.S. allies with Aegis BMD-capable vessels, namely Japan, the Republic of Korea, Norway, Spain and Australia also use the SPY-1.

The SPY-1 radar employed by Aegis Ashore is virtually identical to that used by Aegis Afloat. Currently, there is only one active Aegis Ashore site, which is located at the Deveselu Military Base in Romania, along with one under construction in Poland. There is an additional land-based test facility in Kauai, Hawaii.

SPY-1 Variants

Four different SPY-1 radar variants are currently deployed on U.S. ships. The original SPY-1 variant was a test version of the radar that was never deployed. The SPY-1A and 1B variants are equipped by Aegis cruisers and have two antenna faces on each of the two deckhouses, while the SPY-1D and 1D(V) variants are equipped by Aegis destroyers and have four antenna faces, each antenna covering slightly more than 90° in azimuth. All U.S. Aegis systems that have been upgraded for BMD are equipped with either the 1B, 1D, or 1D(V) version.

  • SPY-1A The SPY-1A was installed on the first Aegis cruiser, the USS Ticonderoga (CG 47), which was deployed in 1981. The U.S. Navy is currently in the process of phasing out the SPY-1A and most Aegis cruisers employ the upgraded 1B variant.
  • SPY-1B This SPY-1 variant has an improved antenna that is better suited to operate in a cluttered environment. The SPY-1B also has around twice the average power of the SPY-1A. 1B is currently employed by most Aegis cruisers.
  • SPY-1D The SPY-1D was the first SPY-1 radar developed for Aegis destroyers. This variant is similar to the 1B version, however, one transmitter is used by the 1D to drive all four radar faces, which are all located on a single deckhouse. This upgrade also improves the radar’s performance against low-altitude, reduced radar cross-section targets in heavily cluttered environments and in the presence of electronic countermeasures. The four U.S. destroyers based in Rota, Spain in 2015 as part of the European Phased Adaptive Approach (EPAA) are equipped with SPY-1D radar.
  • SPY-1D(V) Called the “littoral warfare” radar, the SPY-1D(V) improved clutter rejection and moving target detection, enhancing the capability of Aegis radar in cluttered environments.
  • SPY-1F This variant—known as the “frigate array radar system”—is designed for Aegis frigates and is a smaller version of the SPY-1D. While not employed by the U.S. Navy, the SPY-1F is used by Norway on their Fridtjof Nansen-class Aegis frigates.

Current Status

The next effort to modernize the Aegis fleet is called Aegis ACB 20, which calls for a new version of the DDG-51 destroyer equipped with a new radar, called the AN/SPY-6, which is more capable for BMD and Anti-Air Warfare (AAW) than the SPY-1. These new DDG-51 destroyers are currently scheduled to enter service in 2023.

Recent News


2020 (planned): Phase IV of the EPAA mandates a second operational Aegis Ashore missile defense system and corresponding land-based SPY-1 radar be established in Poland.

2015: Aegis Ashore equipped with one land-based SPY-1 radar was deployed in Romania as mandated by Phase III of the EPAA. Four U.S. Aegis destroyers deployed to Spain—as directed by the EPAA—equipped with SPY-1D radar.

2005: The SPY-1D(V) variant is deployed for the first time aboard the USS Pinckney, a Arleigh Burke class destroyer.

1991: The SPY-1D variant was first deployed aboard the USS Arleigh Burke (DDG-51), the first of the Arleigh Burke class Aegis destroyers.

1982: The SPY-1B variant was first deployed aboard the USS Princeton (CG-59).

1981: The first Aegis cruiser, the USS Ticonderoga (CG-47), which was equipped with SPY-1 radar, was commissioned.

1970s: the SPY-1 program began as part of the Aegis weapon system development process. Increased precision track data via radar signal processing upgrades, improving both Long-Range Surveillance and Tracking and engagement capabilities.