Russian space officials say they lost contact to the Soyuz spacecraft and the International Space Station for three hours.
A Russian news agency reported that the glitch in optic fiber network at the mission control center outside Moscow caused the disruption Thursday. A duty officer told the Interfax agency that the problem had been "completely solved."
The Soyuz TMN-20 with a U.S., Russian and Italian cosmonauts blasted off the Baikonur cosmodrome late Wednesday and will dock with the International Space Station early Friday.
The mission control center in the town of Korolyov outside Moscow was built in the late 1950s, and some of its equipment is badly outdated.