[stephen_g]

The satellite command and control is probably the one bit of the network that's actually hardened (possibly even air-gapped), completely proprietary, etc. - that bit is designed by the companies that make $200 million satellites, not the people who make fairly cheap modems and have different priorities.

The current generation of satellites themselves generally do nothing to the data stream - for each of the dozens of spot beams they're transmitting, they generally just take an RF signal from the ground station (multiplexed in various ways up to the satellite) and convert the frequency. Same with the receive path just in reverse.

The actual modulation/demodulation all happens at the ground station. This is because they expect modem technology will improve, but the satellite has to be able to work for 25-30 years. (Though in the industry they are talking about putting more and more 'software defined' functionality on the satellites, but again this will mostly have to go via their secure systems at the ground station, not from the terminals)

So there's basically no way to interact with any 'satellite firmware' unless you're in a very specific location (near their ground station) with extremely specialised gear.