Design of interference filters for the observation of infra‐red emission from atmospheric carbon dioxide by an earth satellite

Detailed proposals are made for the design of a high‐order Fabry‐Perot type interference filter in which the transmission bands of the filter are exactly matched to 15 lines of the R ‐branch of the CO 2 spectrum near 15 μ. The striking energy advantages of such an interferometer are discussed and it is shown that use of an optically worked high‐index germanium spacer leads to a further considerable increase in light grasp. It is concluded that technical problems are not severe and a calculation of the energy that can be collected by the proposed system suggests that a detector of area 9 mm 2 with a noise‐equivalent‐power of 10 −10 watts (i.e. comparable with a standard Golay cell) can provide adequate sensitivity.