The upcoming launch of the ninth Global Positioning System IIF series satellite (GPS IIF-9)  will be the last of the IIF series to take place on a Delta IV rocket.

The Air Force and launch provider United Launch Alliance (ULA) will launch GPS IIF-9 on Wednesday from Cape Canaveral Air Force Station, Fla. Launch window opens at 2:36 p.m. EDT.

Artist's illustration of the GPS IIF satellite. Photo: Boeing.
Artist’s illustration of the GPS IIF satellite. Photo: Boeing.

GPS IIF-9 mission director Air Force Col. Kent Nickle told reporters in a conference call Friday the next two GPS IIF missions scheduled for later this year will take place on Atlas V rockets, which are cheaper than the Delta IVs. ULA CEO Tory Bruno announced recently that the company would retire the Delta IV rocket in the 2018-2019 timeframe (Defense Daily, March 18). Nickle added that the GPS III series satellites will be launched on both Atlas V and Delta IV.

“ULA has had no less than 29 successful missions on the Delta IV, and this is the sixth, I believe, GPS IIF launch on it,” Nickle said. “Our experience over the years has been very positive.”

Nichols said the Air Force traditionally spreads the GPS IIF launches among the two launch systems as part of its assured access to space policy: if something happens to one rocket, the service can launch satellites on the other launch system. Despite the looming retirement of the Delta IV, Nickle expects assured access to continue as new entrants are expected to be certified this year to compete for military space missions, known as the Evolved Expendable Launch Vehicle (EELV) program. Potential new entrant Space Exploration Technologies Corp. (SpaceX) expects to be certified with its Falcon 9 rocket by June.

There are 12 total satellites in the GPS IIF series, the remaining two are in storage. Air Force spokeswoman Alicia Garges said Friday a GPS IIF launch was set for June, but the launch of the final GPS IIF satellite had not been set.

ULA is a joint venture of Lockheed Martin [LMT] and Boeing [BA]. GPS IIF is developed by Boeing.