United Launch Alliance called off a test-firing of the company’s first flight-rated Vulcan Centaur rocket at Cape Canaveral Thursday to troubleshoot a problem with the booster’s engine ignition system.

Rocketing through gloomy skies with a payload clouded in a veil of secrecy, a United Launch Alliance Atlas 5 rocket fired away from Cape Canaveral on Tuesday to deploy a satellite thousands of miles above Earth.

For its first mission of the year, SpaceX launched the Airbus-built Turksat 5A communications satellite to cover Turkey, the Middle East, Europe, and Africa with data relay and television broadcast services. A Falcon 9 rocket lifted off from pad 40 at Cape Canaveral Space Force Station at 9:15 p.m. EST Thursday (0215 GMT Friday).