Concept and design of a universal command and data interface for Space Shuttle payloads

This paper describes a method to satisfy the command and data requirements of Space Shuttle reflight payloads. These instruments may fly on different carriers at different times, in each case interfacing with a different data system. An example is a payload which normally uses the Spacelab command and data system which is then flown on an Orbiter mission. An Avionics Adapter is one approach. This assembly, when combined with an Orbiter Remote Terminal Unit, becomes a Universal Command and Data Interface (UCDI). It provides an in-flight emulation of the Spacelab Remote Acquisition Unit along with other Orbiter and Spacelab avionics and software services. This command and data assembly can be configured to appear to the payload as one of several possible avionics complements, including the Multiplexer/Demultiplexer, Remote Acquisition Unit, High Rate Multiplexer, Payload Data Interleaver, and Ku-Band Signal Processor. How the UCDI has been implemented is discussed, including as an example the reflight of a Spacelab ATMOS instrument on an Orbiter mission.