Telemetry: Summary of concept and rationale

This report presents the concept and supporting rationale for the telemetry system developed by the Consultative Committee for Space Data Systems (CCSDS). The concepts, protocols and data formats developed for the telemetry system are designed for flight and ground data systems supporting conventional, contemporary free-flyer spacecraft. Data formats are designed with efficiency as a primary consideration, i.e., format overhead is minimized. The results reflect the consensus of experts from many space agencies. An overview of the CCSDS telemetry system introduces the notion of architectural layering to achieve transparent and reliable delivery of scientific and engineering sensor data (generated aboard space vehicles) to users located in space or on earth. The system is broken down into two major conceptual categories: a packet telemetry concept and a telemetry channel coding concept. Packet telemetry facilitates data transmission from source to user in a standardized and highly automated manner. It provides a mechanism for implementing common data structures and protocols which can enhance the development and operation of space mission systems. Telemetry channel coding is a method by which data can be sent from a source to a destination by processing it in such a way that distinct messages are created which are easily distinguishable from one another. This allows construction of the data with low error probability, thus improving performance of the channel.