SpaceX launched a secret U.S. satellite into orbit today. The initial planned launch on Sunday could not happen due to sensor issues, according to NASA Space Flight. SpaceX used its famous Falcon 9 rocket for the launch.

The satellite is from the U.S. National Reconnaissance Office, and is part of the NROL-76 classified mission.

In 2012, SpaceX became the first commercial company to reach the International Space Station. The Falcon 9 helped SpaceX’s cargo-carrying Dragon spacecraft reach the ISS.

In the future, NASA and SpaceX plan to use the same system to send astronauts into space.