The European Space Agency has developed a new compression system, initially designed to be used on so-called ‘smart’ space and satellite missions and telemetry to and from the craft.
The ESA says its spacecraft operations engineer David Evans has invented a family of telemetry compression methods, one of which is about to turned into a data compression standard by the Consultative Committee for Space Data Systems (CCSDS), a multinational forum for the development and sharing of data standards and best practices.
“The challenge is that the amount of telemetry has gone up tremendously, while our bandwidth hasn’t. There are thousands and thousands of parameters available; we need to get as many as possible of them into the ground system, as fast as possible, without affecting the main mission,” said Evans.
“I got involved with a project on smart telemetry to do just that, but discovered it was more complicated than it seemed. While there is a lot of redundancy in telemetry, it simply doesn’t compress well with simple, fast algorithms. We tried it with one standard CCSDS compression software and the size of our data actually expanded,” he added, explaining: “It’s like having of dozens of different authors all writing their own books in various languages, but it’s all being written down together at the same time.”
“This causes problems for compression algorithms that are searching for repeated elements then avoiding having to transmit them all. There’s no way an algorithm can sort this mess out to find the repetition without some help to work out what’s what,” concluded Evans.
The ESA system is called ‘Pocket+’ and there’s also a further development (Pocket++) which delivers added performance benefits in certain conditions.