Start Date

4-1968 8:00 AM

Description

For many space missions , the ability of spacecraft sensors to acquire meaningful data may surpass to a considerable extent the ability of the telemetry system to transmit this data to earth. It is often possible , however, to receive at the Earth a large portion of the sensed data by preprocessing or compressing the data before transmission in order to remove redundancy or useless information. This paper discusses data compression as applied to space missions. Since the usefulness and form of data compression is dependent to some extent on the particular space mission under consideration, certain general classifications of space missions are considered in light of their amenability to data compression. Some basic compression techniques are applied to example sets of data, and the results show that a rather small increase in onboard data processing can result in a severalfold increase in the amount of data transmitted to Earth. The compression procedures used are limited to those easily implemented by the unsophisticated but highly reliable data processing equipment likely to be present on future spacecraft. Curves are developed showing the compression ratio of various techniques as a function of allowable approximation error and complexity of mechanization. Data compression relationships as functions of reliability are also presented, where reliability is related to the loss of data per bit error in transmission. This analysis shows that certain tradeoffs exist since , in general , higher compression ratios are obtained at the expense of less accurate data representation, more complex implementation, and higher loss of data per bit error in transmission.

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Apr 1st, 8:00 AM

Data Compression for Space Missions

For many space missions , the ability of spacecraft sensors to acquire meaningful data may surpass to a considerable extent the ability of the telemetry system to transmit this data to earth. It is often possible , however, to receive at the Earth a large portion of the sensed data by preprocessing or compressing the data before transmission in order to remove redundancy or useless information. This paper discusses data compression as applied to space missions. Since the usefulness and form of data compression is dependent to some extent on the particular space mission under consideration, certain general classifications of space missions are considered in light of their amenability to data compression. Some basic compression techniques are applied to example sets of data, and the results show that a rather small increase in onboard data processing can result in a severalfold increase in the amount of data transmitted to Earth. The compression procedures used are limited to those easily implemented by the unsophisticated but highly reliable data processing equipment likely to be present on future spacecraft. Curves are developed showing the compression ratio of various techniques as a function of allowable approximation error and complexity of mechanization. Data compression relationships as functions of reliability are also presented, where reliability is related to the loss of data per bit error in transmission. This analysis shows that certain tradeoffs exist since , in general , higher compression ratios are obtained at the expense of less accurate data representation, more complex implementation, and higher loss of data per bit error in transmission.

 

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