Lockheed Martin reports it has assembled the propulsion module of a satellite that will help provide continuous early warning of ballistic missile launches.

The module for the fourth Space-Based Infrared System, or SIBRS, Geosynchronous Earth Orbit was assembled and tested at the company's Mississippi Space & Technology Center and shipped to a facility in California where satellite power and avionics boxes will be added.

"This is a significant production milestone for the fourth GEO satellite and further demonstrates our commitment to delivering SBIRS' unprecedented capabilities to our nation," said Jeffrey Smith, vice president of Lockheed Martin's Overhead Persistent Infrared mission area. "We are now seeing the efficiency benefits from full production on the SBIRS program and look forward to delivering GEO-4 to the U.S. Air Force in 2015."

The SBIRS program delivers missile warning and infrared surveillance information to the president of the United States, the secretary of defense, combatant commanders, the intelligence community and other key decision makers in supporting the country's ballistic missile defense system.

SBIRS also aids in intelligence gathering and in enhancing battlefield situational awareness for warfighters.

The SBIRS program calls for six satellites in geosynchronous Earth orbit. The first satellite received Air Force Space Command Operational Acceptance in May of last year and the second was declared operational in 2013, just eight months after its launch from Cape Canaveral Air Force Station, Fla.

Lockheed Martin said the third SBIRS satellite is preparing for acoustic and thermal vacuum testing and is expected to be delivered to the Air Force by the end of 2014.

The satellite propulsion module maneuvers the satellite during transfer orbit to its final location and also performs on-orbit repositioning maneuvers.