Christmas in orbit for Discovery?

The next launch window for sending the shuttle Discovery to the ISS opens December 17, but it's not clear whether the spacecraft would be ready that date. A mission over Christmas is one possibility, but it's turning out to be harder than expected to find the cause of cracks in the intertank structure on the shuttle's External Tank. Fixing the cracks (not difficult) is no good if they might recur and you don't know why. According to NASA's Bill Gerstenmaier,"We would have liked to have found a most probable cause by now. This is turning out to be a little more complicated from an analysis standpoint....We'll let the data drive where we're heading."