If I understand correctly, SAMP is unfortunately a very decidedly ASCII-only protocol.  Furthermore I guess VOTable seems like a "natural" choice because it's XML and SAMP is based on :sparkles:*XML-RPC*:sparkles: so of course we have to have XML inside of XML inside of XML.  I'm surprised they don't put it in a SOAP envelope too.

That said one imagines it must be possible to send another format.  Even if it were a FITS binary table it could be base64-encoded and sent over.  But then I think the client on the other end would have to know how to deal...