-- History --

Originally conceived during the 1980s Strategic Defense Initiative or “Star Wars” era, the Low Earth Orbit (LEO) component of today’s SBIRS architecture has changed and adapted to evolving threats. The SBIRS Low component will bring an entirely new capability to the warfighter — the ability to track missiles from launch to re-entry and to relay necessary cueing data to missile interceptors before the missiles reach friendly forces.

-- Concept --

When fully operational, the SBIRS Low component will consist of greater than 20 satellites in Low Earth Orbit and will work in conjunction with SBIRS High to provide full global coverage. The primary function of SBIRS Low is to provide precise mid-course tracking and discrimination of objects for the SBIRS MISSILE DEFENSE mission in theater conflicts and attacks against North America. In addition, with its low altitude putting it physically closer to the battlefield and thus allowing for higher resolution, the SBIRS low program is well suited to enhance the other three SBIRS missions of MISSILE WARNING, TECHNICAL INTELLIGENCE AND BATTLESPACE CHARACTERIZATION.

Each satellite will contain two infrared sensors to perform its missions. One sensor, known as the Acquisition Sensor, will be a wide field of view scanning infrared sensor utilizing SWIR technology to watch for bright missile plumes during boost phase. Once the acquisition sensor has located a target, that information is transferred to the second on board sensor, known as the Track Sensor, which is a narrow field of view, high precision staring infrared sensor. Mounted on a two-axis gimbal, the track sensor will be capable of locking onto a target and following it through its mid-course trajectory and into its re-entry phase. By this time, the on-board processing will have predicted the final missile trajectory and warhead impact point. This data will then be relayed to interceptor batteries where it will be used to intercept the incoming missile or warhead.

In addition, the entire constellation will be networked together using inter-satellite crosslinks, thus allowing each satellite to communicate with all other satellites in the constellation. This allows for spacecraft-to-spacecraft “handover” of target tracks. In other words, if satellite “A” is tracking a missile and the target is leaving the field of view of satellite “A,” then that satellite can crosslink to satellite “B” and tell it where to look for the target. Then satellite “B” can continue the tracking function and provide the necessary cueing information to interceptor batteries. If necessary, this type of handover will continue between satellites of the constellation until the target has been destroyed or its infrared energy can no longer be detected.

Utilizing tracking data from SBIRS Low, the area defendable by a single interceptor battery increases dramatically. Whereas systems like the Patriot require that the missile be within view of its ground based radar before it can fire, SBIRS Low will provide cueing information to interceptors while warheads are still far away from friendly forces, thus allowing for multiple interceptor attempts on incoming missiles to increase the likelihood of a successful kill. SBIRS Low will “bridge the gap” between initial launch detection and Ground Based Radar interceptors.

-- Schedule --

The SBIRS Low program is currently in Phase I, Program Definition and Risk Reduction, of the acquisition development cycle — sometimes referred to as the Demonstration and Validation phase. Two contractor teams are producing “proof of concept” demonstration satellites scheduled to be launched in FY 1999.

The first of these two designs is called the Flight Demonstration System (FDS) and will consist of two satellites launched on a Delta II 7420 booster. The prime contractor for the FDS is TRW, Inc. with Ratheon Systems producing the infrared payload.

The second of the two designs is called the Low Altitude Demonstration System (LADS) and will consist of one satellite launched from a Lockheed Martin Launch Vehicle and supplemented by a ground demonstration payload. The prime contractor for the LADS effort is Boeing North American with Lockheed Martin providing the spacecraft bus and launch vehicle.

Once on orbit, these two systems will perform tests and experiments to validate the proof of concept for each design and provide data necessary to support a deployment decision milestone in the year 2000.

Parallel to the Phase I effort, preliminary effort is underway to prepare for Phase II, Engineering, Manufacturing and Development (EMD), that will officially begin in 2001. The EMD phase will utilize data obtained from the Phase I demonstration systems and consist of a full and open competition between contractors that will culminate in early 2001 with the selection of a single contractor to develop the fully operational SBIRS Low system with a projected first launch in late 2004.