With the launch of the 2.4-m Hubble Space Telescope (HST), a decade-old aspiration of astronomers will be fulfilled—to observe the Universe with a telescope of large aperture, superb optical quality, and broad spectral coverage, free from the turbulence, selective absorption, and brightness of the earth's atmosphere. The observatory will carry two cameras, two spectrographs, a photometer, and a fine guidance sensor optimized for astrometry. The wide field and planetary camera is designed to obtain images over relatively wide fields of view, at a modest sacrifice in resolution, primarily at visible and near infrared wavelengths. The faint object camera's design emphasizes the highest achievable angular resolution over narrow fields, primarily in blue and ultraviolet light. The Goddard high resolution spectrograph will be used for high dispersion spectroscopy on relatively bright sources, while the faint object spectrograph sacrifices spectral resolution to achieve very faint limiting magnitudes. The high speed photometer will resolve rapid temporal brightness variations and the fine guidance sensor astrometer will measure the relative positions of stars with unprecedented accuracy.