I suspect it was a misspelling. On the keyboard, "s" and "a" are right next to eachother. The intended word might have been CSAN-2 SSM (Ship-to-Surface? Thats only one of the possible uses of SSM, but it makes sense). I remember reading a while back that the PLAN had equiped some Jianghu's with a beach-attack rocket, could be similar.
Alternately, the misspelling could have been SAM instead of ASM (Anti-Sub munition?). That fits more into the context, and I believe this is correct.
I'm not suggesting either, just throwing it out there.