Evaluation of Close-Up Remote cw-Raman Spectroscopy for In-situ Planetary Exploration

Raman spectroscopy is a promising method for space exploration, especially when searching for past or present life. The weak Raman signal is easily superseeded by comparably strong sunlight, which is necessary for electric power supply and temerature regulation of the spacecraft carrying the instrument. Therefore, it is often claimed that only a pulsed operating mode is feasible for in-situ studies on celestian bodies. Pulsed systems, however, imply a much more complex instrument design and thus higher costs and develepmont effort together with a higher risk of failure. In this work, we investigated the capabilities and limits of continuous wave Raman spectroscopy in daylight. The simulated sunlight has been adjusted to match the solar irradiance in Mars-distance from the sun for the visible spectral range. Surprisingly promising results have been found for measurements in the shadow of the spacecraft or when using a sun block to avoid direct illumination.