The Planetary Fourier Spectrometer (PFS) onboard the European Mars Express mission

The Planetary Fourier Spectrometer (PFS) for the Mars Express mission is an infrared spectrometer optimised for atmospheric studies. This instrument has a short wave (SW) channel that covers the spectral range from 1700 to 8200:0 cm1 (1.2–5:5 mm) and a long-wave (LW) channel that covers 250–1700 cm1 (5.5–45 mm). Both channels have a uniform spectral resolution of 1:3 cm1. The instrument field of view FOV is about 1:6 (FWHM) for the Short Wavelength channel (SW) and 2:8 (FWHM) for the Long Wavelength channel (LW) which corresponds to a spatial resolution of 7 and 12km when Mars is observed from an height of 250 km. PFS can provide unique data necessary to improve our knowledge not only of the atmosphere properties but also about mineralogical composition of the surface and the surface-atmosphere interaction. The SW channel uses a PbSe detector cooled to 200–220K while the LW channel is based on a pyroelectric (LiTaO3) detector working at room temperature. The intensity of the interferogram is measured every 150nm of physical mirrors displacement, corresponding to 600nm optical path difference, by using a laser diode monochromatic light interferogram (a sine wave), whose zero crossings control the double pendulum motion. PFS works primarily around the pericentre of the orbit, only occasionally observing Mars from large distances. Each measurements take 4 s, with a repetition time of 8.5 s. By working roughly 0.6 h around pericentre, a total of 330 measurements per orbit will be acquired 270 looking at Mars and 60 for calibrations. PFS is able to take measurement