SpaceX’s latest GPS III launch was its fourth time launching this type of satellite for the U.S. military, but last Thursday’s mission marked a brand-new milestone: It was the first time a National Security Space Launch (NSSL) mission was conducted on a reused booster.

A SpaceX Falcon 9 rocket took off from Launch Complex-40 at Cape Canaveral Space Force Station in Florida on June 17 at 12:09 EST, carrying the Lockheed Martin [LMT]-built fifth GPS III (SV05). The booster successfully landed on a drone ship in the Atlantic Ocean nine minutes later, and the payload separated just under 1 hour and 30 minutes after liftoff.

“We are building on the successful booster recoveries of GPS III-3 and GPS III-4 last year and making a historic step with the GPS III-5 mission using a previously flown vehicle,” Col. Robert Bongiovi, Launch Enterprise director at Los Angeles Air Force Base said in a news release. “The affordability and flexibility provided with SpaceX’s reused launch vehicles open additional opportunities for future NSSL missions and provide our nation’s warfighters with the advanced capabilities they need.”

GPS provides Positioning, Navigation and Timing signals and is a critical part of national infrastructure, driving an estimated $300 billion in annual economic benefit, according to manufacturer Lockheed Martin. The GPS III satellites are part of a modernization program for the fleet, improved accuracy and anti-jamming capabilities. Once GPS III SV05 is operational, about 16 percent of the 31-satellite constellation will be modernized with the GPS III capabilities.

This particular satellite also establishes the constellation’s Military Code (M-Code) baseline. M-Code is a more secure signal. SV05 will be the 24th M-Code signal-enabled GPS satellite, completing the constellation’s baseline requirement for the more secure signal.

Lockheed Martin said that the next three satellites, GPS III SV06, SV07, and SV08 are complete and awaiting launch dates.

This article was originally published in our sister publication Via Satellite.