I think this is worth pursuing. If it's a simple algorithm then we could port to java. Or have a standalone C executable that the ground station runs.

This would mainly be to compress logs, experiment data or telemetry before it is downloaded. Uploading compressed data that the spacecraft can uncompress is a separate use case if we want patch configuration or code.

In a third seperate use case we can already compress large files and upload them for later download. The spacecraft just treats them as binary data and the ground stations do all the work.

Chris

On Sun, Jun 16, 2024, 18:39 Corey Minyard via pacsat-dev <pacsat-dev@amsat.org> wrote:

I spent some time looking at implementations of compression
algorithms. As Bob pointed out, memory can be an issue with these
libraries. I was hoping to say that zlib (gzip) would be suitable,
but its minimum memory requirement appears to be 128K. There appears
to be a way to reduce that, but it's still probably going to be too
big. Later, better algorithms like bzip are going to be even more
memory intensive.

I searched around and there are a large number of compression
libraries that are free and designed for microcontrollers, with memory
requirements in the hundreds of bytes (or even less!). None are as
good as even zlib, but they are better than LZW (compress) and would
be adequate. Also, more critically, they are designed to compress
small amounts of data efficiently. The trouble then becomes finding
one with a Java implementation, if we are planning to send the
compressed data over the download or uplink.

Is this something worth pursuing?

-corey - AE5KM

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