POCKET+

POCKET+ is an ESA patented, lossless compression algorithm implemented using very low-level instructions such as OR, XOR, AND, etc. It has been designed to run on spacecraft command and control processors with low CPU power available and tight real-time constraints. It is a form of delta compression, meaning each incoming packet can be compressed and transmitted without waiting for the next iteration. Finally it incorporates several mechanisms to allow the decompressor to continue functioning, even if a reconfigurable number of successive packets are lost. This makes it suitable for using in combination with “fire and forget” type protocols in a noisy transmission environments, such as those experienced in space to ground RF links. The core algorithm has been adopted and improved by the CCSDS body and is now an international standard for compressing fixed length spacecraft housekeeping packets.

For more details refer to:

• POCKET+ General Presentation
• Implementing the New CCSDS Housekeeping Data Compression Standard 124.0-B-1 (based on POCKET+) on OPS-SAT-1
• CCSDS 124.0-B-1 standard for “Robust Compression of Fixed-Length Housekeeping Data
• Notes on POCKET+ Implementation

A barebone reference implementation in C is available from this package: pocket-plus-master.tar.gz