IRIG-106 PCM IMPLEMENTATION UTILIZING CONSULTATIVE COMMITTEE FOR SPACE DATA SYSTEMS (CCSDS)

Abstract

Asynchronous data sources such as those associated with Space Based Radar create a unique problem for Time Division Multiplexed (TDM) Pulse Code Modulation (PCM) frame formats. The problem consists of data arrival based on external occurrences such as target tracking, and not due to sampling polls from internal sequencers. Reserved time slots for asynchronous data must be provided within the synchronous TDM telemetry stream. This increases the required bandwidth to transfer collected data to ground sites proportional to the worst case arrival rate of asynchronous data and the maximum latency allowed for the application. Asynchronous data is readily handled by the Consultative Committee for Space Data Systems (CCSDS) recommended formats without the need to increase the bandwidth disproportionately. The recommendation maintains the ability to provide synchronous telemetry data collection and transmission provided by the TDM PCM frame formats. This paper provides an implementation of CCSDS recommendations and addresses the methodology of merging asynchronous and synchronous data sources without the prerequisite increase in bandwidth associated with purely synchronous TDM approaches. Additional implementation details are provided for the implementation of a Telemetry Operation Procedure (TOP) to downlink error free telemetry frames. The TOP is not currently supported within the CCSDS recommendation. The implementation is provided through the Micro Packaged Data Acquisition and Control Systems developed by SCI Technology in Huntsville, Alabama.