Photos: Atlas 5 rocket aims for International Space Station

NASA and Northrop Grumman managers at the Kennedy Space Center decided Tuesday to press ahead with final preparations to launch a NASA scientific research satellite early Wednesday aboard an air-launched Pegasus XL rocket off Florida’s east coast.

The addition of a U.S. Air Force communications satellite has capped the assembly of a 218-foot-tall United Launch Alliance Delta 4 rocket at Cape Canaveral set for liftoff the evening of March 13.

One week after two cosmonauts and a NASA astronaut arrived at the International Space Station for a six-month stay, the three crew members they’re replacing packed up their Soyuz spacecraft for a fiery plunge back to Earth Wednesday evening to close out a 196-day mission.