Fourier interferometers in the far-infrared and sub-millimeter ranges. Comparative study of their performances for spaceborne applications

In the far-infrared and the submillimeter ranges Fourier interferometers feasible for space experiments have been analyzed. The performances of the useful interferometric designs: conventional Michelson interferometer, lamellar grating interferometer and polarizing interferometer have been compared, in particular in terms of spectral efficiency (defined as the ratio between the flux received by the detector and the flux at the entrance of the interferometer). New computation processes now available enable a better resolving power from interferograms recorded along a short optical path difference to be obtained if the signal to noise ratio is sufficient. A Michelson interferometer using a mylar beam-splitter has served as a reference instrument, since its spectral efficiency can be easily known in a simple design. The other experimental concepts have been compared and directly characterized.