First launch of the Antares launch vehicle, combining surplus rocket engines from the Soviet N1 moon rocket program with US-built components. The mass simulator carried instrumentation to measure the launch vehicle environment in preparation for future launches of the Cygnus spacecraft designed to carry cargo to the International Space Station. It also released four cubesats into independent orbits.
Delivered 1,494 kg of cargo to the ISS. After rendezvous with the ISS the station's SSRMS arm grappled it at 10:36 GMT on July 16 and berthed it to the Harmony module at 12:53 GMT. Unberthed at 09:14 GMT on August 15 and released by Canadarm-2 at 10:40 GMT. Deorbited and reentered at 13:15 GMT on 17 August over the South Pacific.