WASHINGTON, Sept. 22  U.S. space company Orbital Sciences Corp. said Sunday that the rendezvous of its Cygnus cargo ship with the International Space Station (ISS) was delayed for at least 48 hours due to a computer data link glitch between them.

The unmanned Cygnus spacecraft was originally expected to be captured by a robotic arm operated by astronauts inside the space station at 7:25 a.m. EDT (1125 GMT) before the issue appeared.

“This morning, at around 1:30 a.m. EDT (0530 GMT), Cygnus established direct data contact with the ISS and found that some of the data received had values that it did not expect, causing Cygnus to reject the data. This mandated an interruption of the approach sequence,” Orbital wrote in a status update on its website.

“Orbital has subsequently found the causes of this discrepancy and is developing a software fix. The minimum turnaround time to resume the approach to the ISS following an interruption such as this is approximately 48 hours due to the orbital mechanics of the approach trajectory,” it said.

Space news website Spaceflight101 reported that the rendezvous was called off when the spacecraft’s navigation system “encountered a compatibility issue” with ISS communications system and “was unable to receive GPS (Global Positioning System) data from ISS.”

Cygnus was launched to the space station on Wednesday on a demonstration mission of proving its capability to reliably deliver cargo, only carrying 1,300 pounds (589 kg) of food, clothing and other items.

Orbital is the second U.S. company to send a commercial cargo craft to the space station. SpaceX was the first company to send its own cargo ship with two successful commercial resupply missions and two demonstration missions under its belt.