Update: Get updates on the approach to the berthing at Twitter / Search – #Cygnus.
Update 2: Background information on this commercial cargo demonstration mission can be found at Orb-D1 COTS Demonstration.
A successful berthing will mean that NASA now has two commercial providers of cargo for the ISS. SpaceX has previously carried out one demo and two operational cargo missions to the ISS.
The entire program, including the development of two rockets (SpaceX Falcon 9 and the Orbital Sciences Antares) and two cargo carriers (SpaceX Dragon capsule and Orbital’s Cygnus module) cost the agency around $900M. This is less than than 2/3 the cost of a single Space Shuttle mission.