Altitude Concomitant Sampling for Venus Mass Spectrometer

Precision atmospheric measurements from the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission will be used to describe columnar chemical variations for a broad range of atomic masses, relative abundances of trace species, and isotope ratios of noble gases. The Gas Processing System (GPS) in DAVINCI’s Venus Mass Spectrometer (VMS) plays a critical role in this characterization. While the GPS is still under development, flow simulations were performed with a simplified computational model to inform trade studies and to examine the nuances of timestamping samples admitted into the Quadrupole Mass Spectrometer (QMS). We use fluid physical parameters to derive temporal signatures for QMS scans, in relation to the altitudes from which samples are retrieved. Samples are considered concomitant when the residence time of “old” atmosphere is minimized. Assuming it is possible to sample across an integrated section of plumbing, preliminary results indicate that the GPS could operate at 95% measurement concomitance with altitude, on average. The method applies to laminar pipe flow, without accounting for thermal convective mixing, Taylor diffusion, or secondary friction losses. For continuous sampling applications, targeting a high level of concomitance alleviates some aspects of data uncertainty that could be associated with temporal smearing.