THE CORE STRUCTURE OF THE US Navy's fourth SBIRS geosynchronous satellite (GEO-4) has been delivered to Lockheed Martin. A team of engineers and technicians at the company's Mississippi Space & Technology Center (Stennis, MS) will now integrate the spacecraft's propulsion subsystem.

Featuring a mix of GEO satellites (see photo), four highly elliptical orbiting (HEO) payloads, and associated ground hardware and software, SBIRS is intended to bolster the nation's missilewarning capabilities. In addition, it will contribute to missile defense, technical intelligence, and battlespace awareness. The GEO-4 structure, which is identical to its three predecessor spacecraft, is made from lightweight, high-strength composite materials. It is designed to withstand the accelerations and vibrations generated during launch and support the spacecraft throughout onorbit operations.

Once the Lockheed Martin team has finished integrating the propulsion subsystem with the core structure, the module will be shipped to the company's facility in Sunnyvale, CA for final assembly, integration, and test. (That core is essential for maneuvering the satellite during transfer orbit to its final location, as well as for conducting on-orbit repositioning maneuvers throughout its mission life.) SBIRS GEO-4 is scheduled to be available for launch in 2015.

Lockheed Martin's SBIRS contracts include four HEO payloads; four GEO satellites; and ground assets to receive, process, and disseminate the infrared mission data. It is anticipated that funding for long-lead parts procurement for the fifth and sixth GEO satellites will be received by the end of the year. Under the Air Force's Overhead Persistent Infrared (OPIR) Space Modernization Initiative (SMI), Lockheed Martin also will develop technologies to improve capability and affordability for future SBIRS spacecraft.

The SBIRS team is led by the Infrared Space Systems Directorate at the US Air Force Space and Missile Systems Center (Los Angeles Air Force Base, CA). Lockheed Martin is the SBIRS prime contractor, while Northrop Grumman is the payload integrator. Air Force Space Command (Peterson Air Force Base, CO) operates the SBIRS system.