A synthesis method is outlined for the design of broadband antireflection coatings for use in spaceborne infrared optics. The Golden Section optimization routine is used to make a search, using designated non-absorptive dielectric thin film combinations, for the coating design which fulfills the required spectral requirements using the least number of layers and different materials. Three examples are given of coatings designed by this method: (i) 1 micrometers to 12 micrometers antireflection coating on Zinc Sulphide using Zinc Sulphide and Yttrium Fluoride thin film materials. (ii) 2 micrometers to 14 micrometers antireflection coating on Germanium using Germanium and Yttrium Fluoride thin film materials. (iii) 6 micrometers to 17 micrometers antireflection coating on Germanium using Lead Telluride, Zinc Selenide and Barium Fluoride. The measured spectral performance of the manufactured 6 micrometers to 17 micrometers coating on Germanium is given. This is the antireflection coating for the Germanium optics in the NASA Cassini Orbiter CIRS instrument.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.