At NASA’s Kennedy Space Center, workers have finished the pre-launch assembly and fueling of OSIRIS-REx for the asteroid sample return spacecraft for liftoff Sept. 8.

United Launch Alliance’s Delta 4-Heavy rocket lifted off at 11:10 a.m. PST (2:10 p.m. EST; 1910 GMT) Saturday from Vandenberg Air Force Base, California, after a month-long delay to troubleshoot a hydrogen leak in one of its boosters. The heavy-lifter was on a mission to send a U.S. government spy satellite into orbit.

Delays have set up the possibility of up to three rocket launches this weekend from different pads along Florida’s Space Coast, including two SpaceX missions on Sunday that could set a company record for the shortest span between two Falcon 9 rocket launches. But in the world of ever-changing launch schedules, numerous factors such as weather and technical issues could thwart launch plans this weekend.