Plans by Orbital Sciences Corp. and NASA to rendezvous Orbital’s Cygnus cargo capsule with the International Space Station early Sunday were delayed by two days to overcome a navigation communications discrepancy between the two spacecraft.

Orbital quickly diagnosed the issue that surfaced about 1:30 a.m., EDT, and prepared a software patch which was to undergo testing in a ground based simulator before being transmitted to the orbiting freighter for further evaluation. A successful out come, was to prompt the start of a second rendezvous attempt by Cygnus with the space station late Monday. The changes would guide the Cygnus, with its 1,570 pounds of crew provisions, within range of the station’s 58-foot long Canadian robot arm early Tuesday.

European Space Agency astronaut Luca Parmitano and NASA astronaut Karen Nyberg will be positioned at an internal station control post for the station’s Canadian robot arm ready to grapple the Cygnus capsule as it reaches a point 35 feet below the orbital outpost.

The grapple was to occur Sunday at 7: 35 a.m. EDT, well after the  difficulties surfaced.

The mission, launched Wednesday from the Mid Atlantic Regional Spaceport inVirginia, is being conducted under an agreement between Orbital and NASA’s Commercial Orbital Transportation Systems program.

The 5 ½ year agreement is intended to produce a secondU. S.commercial re-supply capability for the six person space station in the aftermath of the shuttle program’s retirement in 2011.

SpaceX completed NASA COTS program requirements in May 2012 and has since launched two cargo missions under a under 12 mission, $1.6 billion Commercial Resupply Services contract with NASA’s space station program.

Mission success for Orbital clears the Dulles,Va., based company to execute an eight flight, $1.9 billion Commercial Resupply Services agreement with NASA’s ISS program. Orbital’s inaugural CRS flight is tentatively planned for December.

Once berthed to the station’sU.S.segment, Cygnus will remain attached about 30 say. The crew provisions will be exchanged for space station trash before Cygnus departs.