NASA will try to launch space shuttle Endeavour again Wednesday, after repairing a hydrogen gas leak that thwarted the first attempt.

Top officials decided Monday to bump an unmanned moon mission so Endeavour could have another shot at flying to the international space station. The delayed moon mission is NASA’s first in a decade and is critical to the space agency’s long-term effort to return humans to the lunar surface.

The Atlas V rocket had been scheduled to blast off Wednesday with a pair of lunar probes — a moon-mapping orbiter and a craft meant to crash into a shadowed crater at the moon’s south pole. That launch is now scheduled for no earlier than Thursday; it would slip to Friday if the shuttle countdown proceeds trouble-free into early Wednesday.