WASHINGTON — United Launch Alliance completed the last launch of a Delta 4 Medium Aug. 22, sending a GPS-3 satellite into a medium Earth orbit for the U.S. Air Force. 

The Delta 4 Medium rocket lifted off at 9:06 a.m. from Space Launch Complex-37 at Cape Canaveral Air Force Station in Florida. The GPS-3 satellite, nicknamed Magellan, separated from the rocket 1 hour and 56 minutes later. 

The launch was the 29th mission for Delta 4 Medium, a Boeing-originated vehicle that first took flight in 2002. ULA took over Delta launches in 2006 when it formed as a joint venture of Boeing’s and Lockheed Martin’s launcher businesses.

“It was time for us to phase out the Delta 4 Medium at this point,” Gary Wentz, ULA’s vice president of government and commercial programs, said during an Aug. 20 teleconference. “We don’t see any specific payloads that would require the Delta 4 Medium that we can’t fly on an Atlas 5.”

ULA is ending use of the Delta family of rockets in order to eliminate the expense of keeping multiple vehicles in production. The lighter Delta 2 had its final flight in September 2018. Delta 4 Heavy, the “triple core” version of the Delta 4, has five more missions on manifest before its expected retirement in 2023

Wentz said the company’s next-generation rocket, Vulcan Centaur, is slated to debut in April 2021. That vehicle will eventually replace all Delta launchers and the Atlas 5, a Lockheed Martin-originated vehicle used for launching civil, military and the occasional commercial spacecraft. Congress mandated ULA stop using the Russian supplied RD-180 engine — part of the Atlas 5’s first stage — for national security launches by 2022. Vulcan Centaur’s first stage will be powered by two domestically built BE-4 engines from Blue Origin.

The Delta 4 Medium lifted off on its final mission powered by two solid-fueled strap-on boosters from Northrop Grumman and a cryogenic RS-68A first-stage engine from Aerojet Rocketdyne. The rocket carried its GPS-3 payload to a transfer orbit, where it will use onboard propulsion to join the Air Force’s other 31 GPS satellites in a 20,200-kilometer medium Earth orbit.

GPS-3 constellation grows 

The GPS-3 satellite onboard ULA’s final Delta 4 Medium was the Air Force’s second satellite in the series. The first was launched by SpaceX in December on a Falcon 9 rocket.

Each GPS-3 satellite has eight times as the signal jamming resistance of the previous generation of satellites, the GPS-2Fs, and has signals three times as accurate. L3Harris provides the navigation payloads. 

The Air Force selected Lockheed Martin in 2008 to build the first 10 GPS-3 satellites, but opened subsequent satellites to competition after experiencing delays and cost overruns. The Air Force ultimately chose Lockheed Martin again in 2018 for up to 22 follow-on satellites valued at $7.2 billion after Boeing and Northrop Grumman chose not to bid.

The Air Force and Lockheed Martin now say the GPS-3 program is shedding cost as it gains production efficiency. 

“The first two were a little over half a billion dollars [each],” Maggie Sullivan, the Air Force’s GPS-3 program manager, said during the teleconference. “By satellite 10, we will be under $200 million.”

Johnathon Caldwell, Lockheed Martin’s vice president of navigation systems, said the first few GPS-3 satellites bear higher costs from non-recurring engineering work. Once the first few are completed, others get cheaper to build. 

“You gain tremendous efficiencies when you have production volume, and you get a commensurate cost reduction,” he said. 

GPS-3 satellites have a design life of 15 years — the same as most commercial geostationary communications satellites, but 25% longer than the legacy GPS-2F spacecraft. 

GPS-3 satellites also support a new civilian signal called L1C. Sullivan said Europe’s Galileo satellites carry the same signal, meaning end users can boost positioning accuracy through interoperability. 

The Raytheon-supplied OCX Block 0 ground control system will guide the second GPS-3 satellite through checkout and calibration, as it did the first satellite.  Lockheed Martin said Aug. 22 that the Operational Control Segment software updated it completed in May is currently undergoing preparations for installation. That system is for flying the GPS-3 satellites until Raytheon’s OCX Block 1 is ready in 2021.

Sullivan said the next GPS-3 launch is scheduled for January on a SpaceX Falcon 9 rocket.

Caleb Henry is a former SpaceNews staff writer covering satellites, telecom and launch. He previously worked for Via Satellite and NewSpace Global.He earned a bachelor’s degree in political science along with a minor in astronomy from...