Live coverage: Orion lands in Pacific

The countdown began Saturday evening and will continue through the start of a simulated launch window opening at 9 p.m. EST Monday. The test started two days late because of predicted arctic weather along Florida’s Space Coast.

Two NASA astronauts and an Italian flight engineer took shelter in the space station’s Russian segment Wednesday as mission control analyzed a possible leak of toxic ammonia coolant aboard the complex. Initial data indicated it was likely a false alarm.

SpaceX launched its 12th Falcon 9 rocket of the year Thursday from California with Taiwan’s Formosat 5 Earth observation satellite. The two-stage rocket lifted off at 11:51 a.m. PDT (2:51 p.m. EDT; 1851 GMT) and deployed the Taiwanese-built spacecraft into polar orbit. The Falcon 9’s first stage booster successfully landed on a drone ship downrange in the Pacific Ocean.