MT LAUREL, New Jersey — SpaceX launched the U.S. Air Force’s newest GPS satellite Dec. 23 on a Falcon 9 rocket, completing the company’s 21st and final launch of the year.

The rocket lifted off at 8:51 a.m. Eastern from Cape Canaveral, Florida, following technical and weather-related delays that pushed the mission out five days. Its payload, the first GPS 3 satellite from Lockheed Martin, separated from the rocket one hour and 59 minutes later.

The launch was a double milestone for SpaceX, setting a new record over last year’s 18 launches, and fulfilling the company’s first defense mission competed through the Air Force’s Evolved Expendable Launch Vehicle program.

SpaceX’s record annual performance, which included the first-ever launch of a Falcon Heavy, was nonetheless short of the company’s initial forecast of 30 to 40 launches. SpaceX has increased its launch cadence rapidly, up from eight missions in 2016 and six in 2015 (Falcon 9 failures in both those years limited launch rates).

SpaceX has launched other national security missions, such as the National Reconnaissance Office’s classified NROL-76 satellite and the Air Force’s X-37B uncrewed spaceplane, both in 2017. The Air Force has selected SpaceX to launch another four GPS 3 satellites in addition to today’s mission.

SpaceX did not recover the Falcon 9 first stage, having devoted fuel that would have been used to land the booster instead to mission requirements for lofting the 4,400-kilogram satellite into a highly elliptical orbit. From there the satellite will circularize into a medium Earth orbit, joining the U.S.’s GPS constellation of 31 older satellites delivering positioning, navigation, and timing services to more than four billion users.

The new GPS 3 satellite replaces an aging GPS 2R spacecraft launched in 1997.

Lockheed Martin is building the first 10 GPS 3 satellites through contracts awarded in 2008 and 2016. This September the Air Force selected Lockheed Martin to build up to 22 more GPS 3 satellites after reopening the program to competition amid schedule delays and cost overruns.

The GPS 3 program is more than four years behind its original schedule for a first launch.

Lockheed Martin said it has addressed the problems that beset the first few satellites, but the company was aided in winning the additional GPS 3 builds by the absence of Boeing and Northrop Grumman — two anticipated contenders that ultimately chose not to bid in the Air Force’s recompete.

GPS 3 broadcasts a stronger signal to counter electronic jamming. It will be the first GPS satellite to broadcast four civil signals, and the first to do launch and control checkout with the Air Force’s new ground control system: OCX Block 0.

Because it’s the first of its kind, the checkout of the new satellite could take from six to nine months. On orbit checkout will begin about 10 days from launch. Once it’s declared operational, about six to nine more months of tests are planned to integrate the new satellite into the constellation.

Lockheed Martin has manufactured 18 of the 31 GPS satellites currently in operation. The first GPS 3 vehicle is estimated to cost $529 million. It was nicknamed “Vespucci” after the Italian explorer.

The GPS 3 satellites Lockheed Martin is building are designed to operate for at least 15 years. The Air Force intends to launch the second GPS 3 satellite next year.

SpaceNews Staff Writer Sandra Erwin contributed to this article.