you can create and manage completely off line a bitcoin wallet (check glacier protocol).
The blockchain is still on the internet.
you can also receive block through satellite and not just internet.
The sattellite is connecting to the internet, isn't it?
And, The blockchain is still on the internet.
you can verify a signature by your self it means any tx even without internet.
if is still on internet, (blockchain) try to modify it.
satellite doesn't need internet to work. there is a product that allow to receive/send tx without internet
https://blockstream.com/satellite/