First? In 2007, DARPA along with Boeing, Ball Aerospace and other team members, flew the very successful Orbital Express mission in which two unmanned spacecraft conducted rendezvous and docking operations, followed by hydrazine fuel transfer (both pressure-driven and pump-driven) from Boeing’s ASTRO spacecraft to Ball’s NextSat and back again from NextSat to ASTRO.
First between mass produced satellites instead of one-offs, at the very least.