Maybe it's because of RS codes superior performance during burst errors while the SNR involved isn't so low as to give convolutional codes a net advantage. Maybe it's Error Floor.
Or maybe we should just assume that some of the world's most qualified RF and comms engineers behind these decisions did their homework.
maybe because online codes only came available after 2004, and the choice was already made and the picked solution sufficed so was never revisited. So the question becomes: when did they do their homework?
Yes, there is a thread to that effect. Development was heavily delayed, certification and conservatism around space systems can slow down deployment to the point of just not being worth changing things.
I am sorry to have been presumptuous. There's been a spate of recent armchair experts with some arrogant "they should just use a warp drive" type contributions lately.
- The thing with online codes is that while they are quite efficient in data overhead (a few %) they only start working when you have enough data ( > X MB). (check!)
- another problem is that since the system that you need to solve to get your data back is large and random, so in-place updates of the data are impossible. In other words: they only work for immutable data (check!)
- The extra information to counter lost messages is scattered over all messages so the client doesn't need to figure out which ones are missing (and doesn't need to tell the server, in this case the telescope). This makes them highly suited for high latency communication (and storage which is in essence the same thing, but that's another story) (check!)
They (online codes) were designed for this exact use case.
Or maybe we should just assume that some of the world's most qualified RF and comms engineers behind these decisions did their homework.