VIDEO: Expedition 42-43 mission preview

Concern about a possible ammonia coolant leak Wednesday prompted astronauts on the International Space Station to evacuate the U.S. segment of the complex and shelter in the Russian portion of the outpost while flight controllers scrambled to untangle initially confusing telemetry.

Soyuz TMA-15M commander Anton Shkaplerov, flanked on the left by flight engineer Samantha Cristoforetti and on the right by NASA astronaut Terry Virts, are scheduled for liftoff from complex 31 at the Baikonur Cosmodrome in Kazakhstan on Sunday.

Russia launched a Progress resupply mission Tuesday heading for the International Space Station with more than 6,000 pounds of fuel, supplies and experiments to support the lab’s six-person crew, and the automated cargo craft sailed to a smooth link-up with the complex less than six hours later.