Optical Design and Performance of the Planetary Fourier Spectrometer (PFS)

Kurzfassung

The Planetary Fourier Spectrometer (PFS) is a two-channel Michelson interferometer operating in the IR from 1.25 to 45 muem. Two retroreflectors are mounted on brackets enclosing an angle of 90. They are fixed on an axle drove by a torque motor. The angular movement of the retroreflectors concerning the beamsplitter generates the optical path difference. The two primary degrees and the one secondary degree of freedom for misalignment are derived. The pattern of interference fringes, typical for the different types of misalignment, will be simulated. Their use for alignment will be demonstrated. This interferometer design is very robust against slight misalignmet in harsh environment compared with the classical Michelson-type interferometer. This favours the design for applications in space. PFS is intended for the mission Mars '96. It is optimised for the study of the Martian atmosphere.The spectra will also be used for investigations of the Martian soil.