Sensors failed to signal fuel valve’s status. But further tests may allow officials to “relax” a rule.
Unless the valves are in working order, Discovery will remain Earthbound. Previous shuttle missions have encountered problems with the components, too.
The comparatively low-key mission, scheduled to launch at 1:36 a.m. Tuesday, marks the winding down of the space shuttle program.
Koichi Wakata, the first Japanese astronaut to return from a long space journey, greeted friends after 4-1/2 months.
NASA takes it slow and steady as team installs batteries.
The system allows real-time tracking of even small birds up to five miles away.
The space shuttle Endeavour won't launch until July, as NASA engineers try to fix a persistent leak in its external tank.
The delayed launch of Endeavour – caused by a fuel tank leak similar to one that delayed the shuttle Discovery in March – also bumps the launch of a moon reconnaissance mission to Thursday.