XTCE as a Unifying Model for Flight and Ground Software: Experience with the VIPER Mission

Spacecraft and ground systems need a common definition of telemetry and command formats to be able to communicate with each other. The complexity of modern missions makes a traditional document-based interface definition difficult, so a common modeling language is preferable. The NASA VIPER mission uses the XML Telemetric and Command Exchange (XTCE) standard as this common definition for modeling telemetry and command formats, raw-to-engineering conversions, encodings, and algorithms.

While the use of XTCE as a unifying language for both flight and ground operations has been successful, there are areas where plain XTCE has been insufficient, requiring additional processing and information to support different testing and flight environments. In addition, differing needs of flight and ground systems have necessitated other workarounds to limitations in XTCE modeling. This paper will describe the use of XTCE within the VIPER mission, showing ways that XTCE mechanisms have proven useful as well as methods that have been used to overcome XTCE limitations. The conflict between the goals of mission software development and that of XTCE will be analyzed and possible mitigations suggested.