KENNEDY SPACE CENTER - Shuttle launch control is holding at T-3:00 as teams discovered a leak of gaseous hydrogen from the ground umbilical carrier plate (GUCP), the same problem that prevented the shuttle Endeavour from launching on June 13. Tanking operations, already three hours behind schedule due to thunderstorms late June 16, are on hold.
Engineers are cycling the vent valves to see if the hydrogen level drops. Since the issue was discovered around 1 a.m. this morning, the vents have been cycled at least twice. After the second cycling, engineers noticed a "different signature," and a drop in hydrogen levels to levels that are closer to acceptable.
The countdown is holding at three hours out for now. Engineers have reinstated a "fast flow" of liquid fuel to cycle the vents one more time.