The US Air Force (USAF) has ordered two more evolved expendable launch vehicles (EELV) from United Launch Alliance to launch GPS and military communications satellites, a contract worth nearly $400 million.
The order comprises one Lockheed Martin Atlas V and one Boeing Delta IV, both scheduled for launch in 2014.
The Atlas is in 551 configuration, the most powerful currently available, with a five-metre payload fairing, five solid rocket boosters and a single RL-10 engine in the Centaur upper stage. The Atlas will launch the fourth mobile objective user system (MUOS) communications satellite for the US Navy.
Though the Delta configuration was not announced, it will be used to launch a global positioning satellite (GPS) for the USAF. Most previous GPS launches have used a Delta medium+ configuration, with a four-metre payload fairing and two solid rocket boosters.