An early bird rocket launch from the Florida spaceport will take to the skies before dawn Thursday when an Atlas 5 lofts a classified U.S. government satellite.

After replacing a faulty inertial measurement system blamed for a scrubbed launch attempt Sunday, a Soyuz rocket headed to space from French Guiana today with five satellites, including the next spacecraft for Europe’s multibillion-dollar Earth observing network and a French experiment to probe the validity of Einstein’s theory of general relativity.

United Launch Alliance scrubbed the launch of a Delta 4-Heavy rocket Wednesday night less than 10 seconds before liftoff from Cape Canaveral, the second such abort suffered by this mission.. The launch of a classified National Reconnaissance Office spy satellite is expected to be delayed at least several more days as engineers assess the cause of Wednesday’s last-minute abort.