Description of Driving Event:
The effects of an adverse environmental condition, specifically, unusually cold weather, are not sufficiently well understood. The amount of ice formed by leaving valves open to prevent freezing inside water pipes was greater than expected. After the STS 51-L launch, photographic documentation revealed that ice released from the pad structures after engine ignition translated further toward the vehicle than predicted. The performance of some complex 39B systems was marginal due to the cold. The number of cameras that failed to operate at liftoff was three times that of the historical average. Instrumentation and analytical models were not adequate to define the unusually cold operating environment in which the launch was conducted. Additionally, the effects of such temperatures on the components of a space shuttle standing on the pad have not been sufficiently determined.