The deployment and retrieval of a satellite designed to study Earth's middle atmosphere along with a test of potential International Space Station hardware highlighted NASA's sixth Shuttle mission of 1997.The Shuttle Pallet Satellite (SPAS) on which the scientific instruments were mounted is a self-contained platform that provides power, command, control and communication with Discovery during free-flight.The Middle Atmosphere High Resolution Spectrograph Instrument (MAHRSI) measured hydroxyl and nitric oxide by sensing UV radiation emitted and scattered by the atmosphere, while the Surface Effects Sample Monitor (SESAM) was a passive carrier for state-of-the-art optical surfaces to study the impact of the atomic oxygen and the space environment on materials and services.The Microgravity Vibration Isolation Mount (MIM) experiment was operated by Canadian Space Agency astronaut Bjarni Tryggvason.The mission lasted a day longer than originally planned due to a threat of ground fog at Kennedy Space Center.