Sea Launch's ocean-going launch pad and command ship are again sailing across the Pacific Ocean after a series of November attempts were thwarted by unusually strong ocean currents that could be linked to a La Nina climate pattern.

File image of Sea Launch rocket platform in foreground and command ship in the distance. Credit: Sea Launch

The second campaign for Sea Launch's critical return-to-flight mission began last weekend when the company's Odyssey launch platform departed its home port in Long Beach, Calif. The Sea Launch Commander control ship set sail on Wednesday, according to Paula Korn, a Sea Launch spokeswoman.

Liftoff of the Zenit 3SL rocket is scheduled for Jan. 15 at 1149 GMT (6:49 a.m. EST). The launcher will orbit the Thuraya 3 mobile communications satellite to serve the Middle East and the Asia-Pacific region.

The flight will be the first for the company since the Zenit's last commercial launch ended in a devastating launch failure that damaged Odyssey one year ago this month. Nine months of investigations, repairs and other preparations were required for Sea Launch to be ready to resume launch operations in November.

But Mother Nature had different plans.

Unusually strong ocean currents and stiff winds repeatedly dogged the launch team, Korn said. The two ships returned to port early last month after spending more than two weeks moored at a mid-Pacific launch site along the equator.

"They said there was a wake behind the platform, even as it held in position without going anywhere," Korn told Spaceflight Now.

The platform's ballast tanks are filled with seawater to stabilize the vessel after arriving at the launch site. Odyssey's crew spends the final three hours of the countdown at the bridge of the Sea Launch Commander, remotely operating the converted oil drilling rig from three-and-a-half miles away to keep its orientation within specific parameters optimized for the rocket's mission.

Both Sea Launch ships use state-of-the-art positioning equipment to control the vessels. The system includes underwater thrusters that can move the ships in all directions, Korn said.

"With these currents coming at the platform with this very high force, station-keeping was not only challenging, but in a few instances, impossible," Korn said.

Officials estimate the currents were two-to-three times stronger than what Sea Launch had previously experienced.

"We determined in November that we were using up fuel just trying to stay in place," Korn said.

Sea Launch later consulted with oceanographers and climatologists to help explain the unusual conditions, and scientists found a potential link to a La Nina currently underway in the Pacific.

Sea surface temperatures across the Pacific. Credit: NOAA. The Sea Launch site is denoted with red dot.

La Nina patterns include colder than normal sea temperatures in the eastern equatorial Pacific. La Nina can also produce extreme weather around the world, according to NOAA.

Korn said the temperature of the water at the launch site decreased by a few degrees within just a couple of days. Such a rapid change in temperature is an indication of an on-going La Nina.

NOAA's Climate Prediction Center reported the La Nina reached moderate strength in November, and forecasters expect the cool ocean temperatures to persist through at least next month.

"There's definitely something up and Sea Launch experienced a global environmental event," Korn said.

The ocean currents and winds finally forced officials to call off further launch attempts and return to California for the holidays.

Teams spent the next few weeks studying the conditions and planning a new strategy for another campaign to raise the chances of a successful launch attempt.

Korn said the platform is carrying extra fuel and power generators to allow the ship to battle strong currents for longer periods of time. Engineers are also evaluating the tight heading and position constraints for the ships to determine if they could be relaxed.

In addition to the new supplies, Sea Launch is now maintaining a log of ocean conditions to try to identify trends. A buoy stationed at the launch site monitors real-time conditions, but there is no accurate method of predicting deep ocean currents.

"We are learning a lot from the experience, about the outstanding performance of the launch platform, about the launch site, about the parameters of our launch requirements," Korn said. "With every challenge that Sea Launch encounters, we learn more."