Web-based weather expert system (WES) for Space Shuttle launch

The Web-based weather expert system (WES) is a critical module of the virtual test bed development to support "go/no go" decisions for space shuttle operations in the Intelligent Launch and Range Operations program of NASA. The weather rules characterize certain aspects of the environment related to the launching or landing site, the time of the day or night, the pad or runway conditions, the mission durations, the runway equipment and landing type. Expert system rules are derived from weather contingency rules, which were developed over several years by NASA. Backward chaining, a goal-directed inference method is adopted, because a particular consequence or goal clause is evaluated first, and then chained backward through the rules. Once a rule is satisfied or true, then that particular rule is fired and the decision is expressed. The expert system is continuously verifying the rules against the past one-hour weather conditions and the decisions are made. The normal procedure of operations requires a formal pre-launch weather briefing held on launch minus 1 day, which is a specific weather briefing for all areas of space shuttle launch operations. In this paper, the Web-based weather expert system of the Intelligent Launch and Range Operations program is presented.