I am certain that I read a year or three ago about an unmanned satellite that was going to be testing a method of attitude determination that relied upon two (or more) separate antennas on one spacecraft, and used the difference in arrival times of GPS signals at the two antennas to calculate an approximate attitude.
I am not sure if it used a standard "relative GPS" implementation (see also this answer and this mathematical discussion), or if it was more advanced because all signals were available simultaneously to one correlator cluster, whereas relative GPS relies on the exchange of digital information using a link between two systems.
@DavidHammen points out in comments that this has been done before. This is not new. It seems examples include the Soyuz spacecraft, the ISS, and even much earlier experiments.
Question: However I'm looking for a recent unmanned satellite and if possible an understanding if it uses relative GPS or a more advanced technique running the output of all correlators from all antennas through a single fitting procedure.