The rocket, along with versions of the military Titan IV and Boeing Delta III, had been grounded due to failure of an RL-10 upper stage engine on a May Delta III flight. Atlas vehicles use the same type of engine system on its upper stage units.

Modifications to engineering, manufacturing and inspection procedures on flight units of the engine were key steps in the release of RL-10-powered launchers to return to flight, said G. Thomas Marsh, Lockheed Martin Astronautics president in Denver.

An Atlas IIAS will launch the EchoStar V on Friday Sept. 10, followed by the launch of the U.S. Navys UHF Follow-on F10 satellite on September 30, both from launch pads at Cape Canaveral Air Station in Florida.

The third Atlas mission will be the NASA Earth Observing System (EOS) Terra-1 satellite aboard an Atlas IIAS out of Vandenberg Air Base California in October. Additional launches may also be scheduled before the end of the year.

There was no word Monday on the fate of the first Atlas III launch vehicle, which is now in storage at Cape Canaveral following cancellation of its satellite payload during the launch delay. The Loral spacecraft was moved to an Ariane 4 booster due to the uncertainty over when the Atlas would be cleared for flight.

The Atlas III is the first U.S. commercial launch vehicle to be lifted using a Russian-made liquid rocket engine, the RD-180. The engines original version, the RD-170, is used to power the Zenit space booster and was used to launch the Energyia vehicle before it was discontinued following the dissolution of the Soviet state.