The UHF relay link through the Mars Odyssey orbiter exceeded expectations of the Mars exploration rover (MER) project and played a critical role in the return of data from the surface of Mars and in the accuracy of the rover position determination. This paper will discus the development and performance of the UHF transceivers and the Consultative Committee for Spacecraft Data Systems (CCSDS) Proximity-1 space link protocol that were used by Odyssey and the two MER rovers; and some of the more prominent lessons learned during development and operations of the MER-Odyssey relay link.