United Launch Alliance called off the planned launch of an Atlas 5 rocket Wednesday at Cape Canaveral to resolve a problem with valves at the launch pad, while a SpaceX team a mile-and-a-half to the south readied a Falcon 9 rocket for liftoff Thursday evening with a GPS navigation satellite for the U.S. military.

Air Force ground controllers have activated service aboard the newest Global Positioning System satellite, achieving that milestone for the final spacecraft in a dozen built in a manufacturing batch to update the constellation.

These photographs span activities in March as the news media got an up-close viewing of the Orbital ATK commercial Cygnus cargo ship, its placement aboard a mobile transporter and delivery of the craft to the United Launch Alliance Atlas 5 rocket assembly building for hoisting and mating. Liftoff is scheduled for April 18.