There was, also, some concern earlier in the morning about ice forming on an umbilical cord for liquid hydrogen on the external tank (ET), which supplies fuel to Discovery’s three engines. However, NASA’s Debris Analysis Team (DAT) cleared the ice as not being an issue for launch.

At about 11:26 a.m. EDT—about twelve minutes before the scheduled launch—NASA mission controllers gave their “go for launch” to the STS-120 launch flight director.
The twenty-third mission to the International Space Station, Discovery is bringing the Harmony module to the station. Eleven missions remain to the ISS, with still two unconfirmed contingency logistic flights.

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