KENNEDY SPACE CENTER, FLA. -- The space shuttle Discovery nears the Orbital Processing Facility, or OPF, where processing Discovery for another flight begins. Towing normally begins within four hours after landing and is completed within six hours unless removal of time-sensitive experiments is required on the runway. Umbilicals are attached to purge the vehicle of any possible residual explosive or toxic fumes. In the OPF, turnaround processing procedures on Discovery will include various post-flight deservicing and maintenance functions, which are carried out in parallel with payload removal and the installation of equipment needed for the next mission. Before post-flight deservicing can continue beyond initial safing operations, certain vehicle systems must be mechanically secured and access platforms installed. Discovery completed mission STS-120 with an on-time landing at 1:01 p.m. EST.