Sea Based X-Band Radar (SBX)

The Sea Based X-Band Radar (SBX) program, managed by the Missile Defense Agency (MDA), is a critical component of the United States' missile defense architecture. The SBX is a highly advanced, mobile radar platform designed to provide mid-course acquisition, tracking, discrimination, and hit assessment of missile threats, particularly intercontinental ballistic missiles (ICBMs). Mounted on a semi-submersible vessel, SBX can be deployed globally to support homeland defense, participate in missile defense system flight and ground tests, and respond to operational contingencies. The primary objective of this program element is to sustain and enhance the SBX's operational readiness and technical capabilities to ensure reliable performance in support of national security missions.

MX46: Sea Based X-Band Radar Development Support encompasses the bulk of the SBX program funding and activities. This line item supports the development, operations, and sustainment of the SBX vessel, the X-Band Radar (XBR) subsystem, and the associated communications network. Key goals include maintaining vessel certifications, ensuring software compatibility with the broader Missile Defense System, and conducting regular maintenance and upgrades. The program also funds participation in integrated ground and flight tests, as outlined in the Integrated Master Test Plan (IMTP), which are essential for validating SBX's capabilities and interoperability with other missile defense assets.

Within MX46, vessel operations and support is a major focus area, providing for the full operational readiness of the SBX vessel. This includes resupply, underway maintenance, annual surveys, force protection, and logistical support such as air charter and supply vessel charters. The objective is to ensure the vessel can deploy rapidly in response to emerging threats and maintain sustained operations during test events or active defense missions. Vessel maintenance also includes compliance with U.S. Coast Guard and American Bureau of Shipping certifications, which are necessary for safe and legal operation at sea.

XBR operations and support is dedicated to maintaining the radar subsystem at peak performance, including routine maintenance, software sustainment, and incremental capability upgrades. In FY 2026, a significant objective is the initiation of a technology refresh and prototyping for the next-generation server architecture, which will enable advanced radar processing and data management. This investment is justified by the need to keep pace with evolving missile threats and to ensure the SBX remains a viable asset for homeland defense through at least 2045.

XBR radome replacement was a targeted effort to address adhesion failures and water intrusion in the radar's protective dome, with production and installation activities completed during the 2025 in-port maintenance period. This project ensures the long-term operational viability of the SBX by protecting sensitive radar components from environmental damage. Similarly, vessel in-port maintenance and upgrades in FY 2025 and FY 2026 focused on overhauling critical vessel systems, including power, propulsion, communications, and safety equipment, to meet readiness requirements and maintain operational certifications.

MD40 program-wide support provides non-headquarters management and support costs for the SBX program and other MDA activities. This includes funding for government civilians, contract support services, deployment site preparation, facility operations, security, audit readiness, legal services, training, and compliance with environmental requirements. The objective is to ensure the integrity and oversight of the Missile Defense System and to support the development and evaluation of technologies that respond to changing threats. Program-wide support is allocated on a pro-rata basis across MDA program elements and fluctuates annually based on the total agency budget.