The next satellite to launch from Cape Canaveral — an essential communications satellite for the U.S. military and allied nations — was moved to the pad and mounted atop its Delta 4 rocket today.

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.

The penultimate satellite in the current generation of Global Positioning System spacecraft will be deployed Friday, capping a hectic four weeks with three launches from two coasts for the Atlas 5 rocket fleet.