Simulation and methods for the data analysis of the hydrogen-deuterium-absorption-cell-experiment on Cassini

Abstract

The Hydrogen-Deuterium-Absorption-Cell (HDAC) will be flown as part of the UltraViolet Imaging Spectrograph on the Cassini mission with the objective to determine the deuterium-to-hydrogen (D/H) ratio in the exosphere of Titan. The HDAC is a photometer designed to measure separately the H and D resonant scattered solar Lyman alpha radiation. A non-parametric reconstruction of the Lyman alpha line profiles by means of local linear filters has been developed for the data analysis. An apriori line profile has been statistically described. Applying a minimum variance criterion leads to systems of linear equations, whose solutions yield the filter coefficients. The quality of the line profiles reconstructed with the proposed algorithm in realistic conditions of observations shows that is workable for the real mission.