I have many qsl cards from hams I have made contact with using packet on the ISS . I don't acknowledge a qso unless He acknowledges My call sign in return . What really takes the time from a pass is when someone has mail and doesn't download it from RS0ISS-11 mail box. Can't get to the repeater when it's trying to deliver mail .

I find NO-44 active for packet , but doesn't get much traffic . It is very hard to reach at times , but still usuable .

I agree also , psk31 would very much limit the contacts made on a pass. I use psk31 on FM and it is very quiet and pleasant to use , but don't think it would make a good digital format for satellite work .

Jerry WB5LHD