Estimating the mechanical properties of loose soil in low gravity based on acceleration measurements

In the context of planetary exploration, it is imperative to predict the mechanical properties of the surface layer, efficiently compensate for the movement of the lander, and acquire information on the properties of the target astronomical body for future missions. To examine the characteristics of the surface layer of the ground on such objects, current methods necessitate the investment of substantial resources such as measuring leg reaction forces, capturing images of pad penetration, or direct measurement with onboard tools. Therefore, in this study, we propose a methodology to estimate the ground characteristics using only a triaxial accelerometer. These devices are commonly installed on landers and rovers. Specifically, during dynamic pad penetration tests conducted in a microgravity environment, we simultaneously measured the reaction force, sinkage, and acceleration, and compared the results. Our results confirmed that the modulus of subgrade reaction calculated from acceleration data is equivalent to that derived from measurements of force and sinkage quantities under the condition of low-velocity contact onto regolith-like terrain such as might be encountered in the exploration of a small body. This facilitates the estimation of the characteristics of the ground and contributes to the mitigation of mission risk and expands our understanding of mechanical properties across a more extensive area. • Method for estimating ground characteristics using accelerometer data was proposed. • Direct measurements were compared using experiments with simulated low gravity. • Ground stiffness can be estimated using data from an accelerometer alone. • The method shows potential in planetary exploration using small probes and landers.