[15] The exact error related to small discrepancies between the way the ISS and Cygnus each use GPS for timekeeping purposes.

[17] A week late, the spacecraft conducted a series of navigation, control and safety tests as it approached the station.

Following the successful completion of ten test objectives, the spacecraft was cleared to make its final approach, holding 12 m (39 ft) below the ISS.

Then, Italian astronaut Luca Parmitano grappled it at 11:00 UTC, on 29 September 2013, using the Canadarm2 Mobile Servicing System (MSS) [8] as the two spacecraft sailed high above the Indian Ocean.

[8] Cygnus Orb-D1 carried 700 kg (1,500 lb) of cargo to the ISS, including food and spare parts.