Three group members, Dr. Jörn Helbert, Dr. Alessandro Maturilli, and Dr. Mario D’Amore are Co-I (co-Investigators) for the Planetary Fourier Spectrometer (PFS) onboard the ESA Mars Express mission.
The PFS instrument
Mars Express, so called because of the rapid and streamlined development time (therefore borrowing technology from the failed Mars 96 Russian mission), represents ESA's first visit to another planet in the Solar System. The mission helps to answer fundamental questions about the geology, atmosphere, surface environment, history of water and potential for life on Mars. The mission just reached its 10 years anniversary of operations, with a possible future extension of at least another 3 years.
The Planetary Fourier Spectrometer (PFS) is a double pendulum Fourier transform interferometer, with a Long Wavelength Channel (LWC) covering the spectral range from 250 to 1700 cm-1 (5.9 – 40 μm) and a Short Wavelength Channel (SWC) measuring in the range from 1700 to 8200 cm-1 (1.2 – 5.9 μm). While the Martian radiation is divided in 2 beams by a dichroic mirror, the two pendulums are moved by the same motor, and the two channels are sampled simultaneously and independently.
We developed a surface-atmosphere-separation (SAS) method allowing to model the atmospheric contribution to the PFS LWC measured spectra. The method for the separation of surface and atmospheric features we implemented is based on a combination of R-mode factor analysis and target transformation. Choosing a large enough dataset allows to coherently affirm that all the possible variability in the data observed can be described to a varying combination of the spectral endmembers. By means of target transformation and factor analysis techniques, LWC PFS data can be successfully modelled as a combination of atmospheric endmembers (recovered from local PFS atmospheric measurements) and a residual surficial component. This surface emissivity spectra is furthermore fitted with a linear deconvolution of BED emissivity spectra to infer the surface mineralogical composition (in weight %) of the area under examination.