CAPE CANAVERAL A traffic jam at the International Space Station is prompting a second delay in the arrival of a new commercial cargo ship that is making a test run to the orbital outpost, officials said on Monday.
The docking of the Cygnus freighter was retargeted for Saturday to avoid conflicting with Wednesday's scheduled arrival of new crew members at the space station.
Orbital Sciences originally had planned to fly the Cygnus to the station on Sunday following four days of maneuvers and communications tests. A problem processing navigation data from the space station early on Sunday forced the rendezvous to be rescheduled for Tuesday.
Resolving the problem with a software fix left Orbital Sciences with a tight schedule to rendezvous and dock the Cygnus capsule at the space station before the Wednesday arrival of a Russian Soyuz spaceship carrying three new crew members.
Station operators need at least 48 hours between arrivals of spacecraft at the orbital outpost, a $100 billion complex that flies about 250 miles above Earth.
"Both Orbital and NASA felt it was the right decision to postpone the Cygnus approach and rendezvous until after Soyuz operations," the company wrote in a status report on its website.
Cosmonauts Oleg Kotov and Sergey Ryazanskiy and NASA astronaut Michael Hopkins are scheduled for launch at 4:58 p.m. EDT on Wednesday from the Baikonur Cosmodrome in Kazakhstan. They should reach the station about six hours later.
"This new schedule will allow the Orbital operations team to carefully plan and be well-rested before restarting the critical final approach to the space station," Frank Culbertson, Orbital's executive vice president, said in the statement. "Meanwhile, Cygnus has all the resources needed to remain in orbit for an extended period of time."
Cygnus blasted off for a debut mission aboard an Orbital Sciences' unmanned Antares rocket from a new spaceport in Virginia on September 18. The company is the second of two hired by NASA to restore U.S. supply lines to the station following the retirement of the space shuttles in 2011.
Competitor Space Exploration Technologies, or SpaceX, which began working with the U.S. space agency about 18 months before Orbital, so far has made a test flight and two cargo runs to the station.