Orbital’s Cygnus cargo ship docking to the ISS has been delayed due to an unspecified software problem.
The Cygnus had established direct data communications with the International Space Station at which time some of the data values received by Cygnus had unexpected values. Those unexpected values caused Cygnus to reject the data and an interruption of the approach sequence was necessary.
The cause of the data problem has been discovered by Orbital and they have a developed a fix.
The next docking attempt will occur no earlier than September 28th due to Wednesday’s launch of a Soyuz from the Baikonur Cosmodrome bringing Michael Hopkins of NASA and Oleg Kotov and Sergey Ryazanskiy of the Russian Federal Space Agency to the ISS. More about that Wednesday.
When docking time does come, Cygnus being a new cargo craft it must as any new cargo craft that is to dock with the ISS must pass a series of objectives in order to prove it is capable. At each of the test points used to measure the objectives a go or no-go order is given by mission controllers before it can proceed to the next point (see image above). There are three more test points between 250 meters and capture. It is only after all of those tests or objectives are met it can then be captured or docked.
See all of the images from the press briefing where the above image came from.