The VS consists of a central heating rod, enclosed by a tubular shell, which is inserted into the ground to enclose a cylindrical volume of regolith. The heating of the enclosed sample releases the bound volatiles. The released volatiles increase the gas pressure inside the tubular shell. This gas will either be lost downwards through the soil or upwards through the orifice to the Volatiles Analyser, which is used to analyse its chemical composition. To calculate the total amount of released gas, and thus the original abundance of volatiles in the soil, the amount of lost gas must be known. To this end, two pressure sensors measure the gas pressure before and after the orifice. This allows the calculation of the amount of gas that has passed from the shell to the VA. To determine the amount of gas lost through the regolith, the VS can be pressurized with a reference gas to a specific pressure. The observation of the pressure loss over time then allows to calculate the gas permeability of the soil. This allows to infer the original abundance of volatiles in the soil.