Acting as a prime contractor to the Gemini PrOJeCt [GPJ, the Optical Data Associates [ODA] . with Its major subcontractors, BOC Coating Technologies IBOCC11 and Deposition Sciences, Inc. IDSII, developed options for depositing protected silver coatings on the 8-M primary mirroi. The project began with a study that identified sputtering as the preferred deposition technique, defined a set of candidate adhesor and protective coatings for the silver layer, and simulated stack performance. The next phase involved pilot magnetron sputtering studies by BOCC and DSI of designs lnvoMng silicon nitride and hafnla, respectively. ODA also developed mid-IR reflectance standards at . = 10.6 pm to control the silver coating measurements In the critical 8-12 pin atmospheric window. The study. results were successful, with both BOCCI and DSI producing Ag coatings with R = 0.9920 0.0001 and protected Ag coatings with R = 0.9910 0.0001 . The Gemini Project coating plants are designed to sputter bare and protected Al and Ag coatings.