A HIGH SPEED REAL TIME SPACE QUALIFIED TIME DIVISION MULTIPLEXED DATA FORMATTER

Abstract

A system to generate a contiguous high speed time division multiplexed (TDM) spacecraft downlink data stream has been developed. The 25 MBPS downlink data stream contains high rate real time imager data, intermediate rate subsystem processor data, and low rate spacecraft housekeeping data. Imager data is transferred directly into the appropriate TDM downlink data window using control signals and clocks generated in the central data formatter and distributed to the data sources. Cable and electronics delays inherent in this process can amount to several clock periods, while the uncertainty and variations in those delays (e.g. temperature effects) can exceed the clock period. Unique (patent pending) electronic circuitry has been included in the data formatter to sense the total data gathering delay for each high speed data source and use the results to control series programmable delay elements to equalize the delays from all sources and permit the formation of a contiguous output data stream.