We had a very interesting video meeting with HTL today. They have built this X-band transponder together with JAXA (if I understood correctly) which flew on a small asteroid mission a few years back. If I remember correctly the propulsion unit failed on that particular one, however the transponder worked wonderfully. They are now building an even smaller and better transponder. After some debate and thinking, it also seems like they might be able to build it ITAR free, something we like. So, seems like there are options for small spacecrafts in deep space!