The scientific objectives of the Large Space Telescope, currently in the preliminary design phase, are summarized in this paper. The conceptual design of the Optical Telescope Assembly (OTA) and system requirements introduced by the Scientific Instruments are also described. LST operations are characterized with emphasis on the fine pointing system, star acquisition, and image motion sensing. The LST is designed for 15 years of useful life, and the Shuttle Space Transportation System will permit earth return for maintenance and equipment updates every 2 to 3 years. Major advances in man's knowledge of the universe are expected to result from the Large Space Telescope.