The core structure for the fourth missile-warning satellite Lockheed Martin is building for the U.S. Air Force’s Space Based Infrared System (SBIRS), known as GEO-4, has been delivered to a Lockheed facility in Mississippi where it will be outfitted with its propulsion system, the company announced in a May 24 release.

Vanguard Space Technologies of San Diego, shipped GEO-4’s core structure — which is made out of lightweight, high-strength composite material — to Lockheed Martin’s Mississippi Space & Technology Center in early May, according to Lockheed Martin spokesman Michael Friedman.

Once the propulsion system is installed, the GEO-4 core propulsion module will be shipped to Lockheed Martin’s Sunnyvale, Calif., facility for final assembly, integration and testing, according to the press release. Lockheed Martin expects to finish GEO-4 on time for a 2015 launch.

GEO-4 is a replica of the first SBIRS satellite, which was placed into geosynchronous orbit in May 2011 and is expected to begin operations before the end of the year.

The second of the four planned geosynchronous SBIRS satellites is slated to launch in May 2013 from Cape Canaveral Air Force Station, Fla., atop a United Launch Alliance Atlas 5 rocket.