The U.S. Air Force’s first Space Based Infrared System (SBIRS) missile warning spacecraft was fueled April 11 in preparation for a planned early May launch, prime contractor Lockheed Martin Space Systems of Sunnyvale, Calif., announced April 13.

Filling the satellite with its hydrazine and nitrogen tetroxide fuel was the final step for the spacecraft before it is mated with its Atlas 5 launch vehicle, the press release said.

Launch of the first SBIRS geosynchronous satellite is nearly a decade late as the Air Force and its contractors have struggled through many technical difficulties. The past few years have been spent rewriting the satellite’s flight software package after an unacceptably high number of glitches were found during testing. All of those difficulties are behind the program now and the satellite will provide incredible new capabilities on orbit, Air Force Brig. Gen. (select) Roger Teague, director of the Infrared Space Systems Directorate, said during an April 12 media briefing.

The first SBIRS geosynchronous satellite will join two SBIRS payloads that are hosted on classified satellites in highly elliptical orbits. The Air Force plans to launch the second SBIRS satellite about one year after the first, Teague said.