Tech Briefs

Software for Lossless Data Compression

Lossless data compression has been employed in space to reduce communication bandwidth requirements for onboard storage for more than 15 years. A widely used space compression standard is the recommendation published by the Consultative Committee on Space Data Systems (CCSDS). The standard describes a simple, efficient, lossless compression scheme that can be applied to data generated from various space instruments such as radiometers, gamma ray detectors, and optical sensors.

The most recent version of the standard expands several parameters to allow for longer specified scanline length, more selection of basic block size, and shorter ID codes for a data range of 4-bit or less, which has proven useful for certain data such as multilevel cloud screen and image signatures created onboard by other processing methods.

A newly created C-code implements both versions of the standard. It compresses input data dynamic range from 1- bit to 32-bit, and offers other features such as the option of only exercising the entropy coding module of the algorithm, as well as several prediction stage options. The coded bit sequence format is fully compliant with the CCSDS specifications.

This work was done by Penshu Yeh of Goddard Space Flight Center. For further information, contact the Goddard Technology Transfer Office at (301) 286-5810. GSC-16579-1