WASHINGTON — Lockheed Martin Space Systems of Sunnyvale, California, shipped a missile warning sensor May 14 for integration aboard a classified satellite that will operate in highly elliptical orbit, U.S. Air Force officials said in a June 16 press release. The infrared sensor, the last of four elliptical-orbit sensors under contract as part of the Space Based Infrared System, will be capable of monitoring missile launches in the northern hemisphere. Three similar sensors have been launched so far. The third sensor, known as HEO-3, launched in 2014 and successfully completed its on-orbit checkout in May, according to a May 15 Air Force press release.
“HEO-4 will complete the replenishment of our polar missile warning capability, ensuring continuity of this critical operational capability,” Air Force Lt. Gen. Samuel A. Greaves, commander of the Space and Missile Systems Center, said in the June 16 release. Lockheed Martin is the prime contractor on the SBIRS program. Northrop Grumman Electronic Systems of Azusa, California, serves as the payload manufacturer and integrator. The nominal SBIRS constellation consists of two HEO sensors and four dedicated satellites in geosynchronous orbit. Two of the geosynchronous satellites have launched to date and Lockheed Martin is under contract for an additional four. The SBIRS program is projected to cost about $19 billion, which is almost four times higher than initial estimates.