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A problem with most compression techniques is that they require a certain amount of data to be stored before the block can be compressed efficiently. This introduces latency onto the link and makes them unsuitable for real-time control where typically small packets are generated and send to the user as fast as possible. POCKET is a unique method that can compress individual packets so fast that this latency is not noticeable. In fact it some cases it even decreases the link latency as the time saved in transmitting a smaller packet more than compensates for the time taken to compress it!
POCKET has been tested using real spacecraft housekeeping data and was found to compress significantly better than ZIP and significantly faster. Average compression ratios of 3 to 20 have been achieved depending the mission.
The result is a simple method that simply compresses packets as they are generated and outputs smaller packets. These can then be decompressed on the other end before being injected into a legacy control system. Hence the system impact is minimal.
POCKET has been prototyped and validated on on-board hardware (LEON2 processor) as part of the PROBA-3 mission. An end to end system is concurrently being bread boarded as part of an ARTES 5.1 study for use on telecommunications satellites. A TRP study will start soon on using it for remote control of robots. The ESA Patent Group has decided to protect POCKET by filing a patent application in the European Patent Office.