Accommodation Study for an Anemometer on a Martian Lander

Measuring the wind velocity and its turbulent fluctuations near the surface of Mars is an important component of the future exploration of Mars, not only to minimize risk in landing, but also to understand some of the most important fundamental processes that dominate Mars' behavior today. Previous missions have included instrumentation to measure 2D mean winds, but a more sophisticated instrument has been designed that allows for fast, precise 3D measurements of the wind and its turbulent properties. These richer observations raise the question of how best to place such an instrument on a future Martian lander to minimize the flow distortions imposed by the lander, and how to correct for the perturbations that cannot be avoided. To carry out this research, computational fluid dynamic simulations in three dimensions were performed using Fluent, a commercially available software. The first step was to model the conditions at the surface of Mars and, more particularly, the quantities describing the flow in the boundary layer. Using these models, simulations were conducted with two simple shapes for the lander and with eight turbulence conditions representing neutral stability flows in the Martian boundary layer. The results are believed to be generally robust for neutral stability cases because the simulations exhibited little variability as a function of the turbulence conditions. This allowed criteria to be established that would optimize the placement of an anemometer in close proximity to a Martian lander under these conditions. The optimal position that has been derived is an elevation of 55 with a minimum distance from the lander of 0.8 times the characteristic size of the lander.