In-situ calibration methods for specialized penetrometers

In-situ calibration methods are essential for enhancing the reliability of specialized penetrometers used in extraterrestrial environments, where traditional Earth-based references are inapplicable. This study introduces a novel approach to in situ calibration using a robotic arm with an integrated scoop and imager to create reference surfaces. The Sample Acquisition, Morphology Filtering, and Probing of Lunar Regolith (SAMPLR) payload is used as a case study to illustrate the proposed methods. By generating low and high-density reference surfaces and employing photogrammetry for volumetric modeling, calibration models are developed to estimate relative density. Experimental results demonstrate the effectiveness of α and β penetration curve fit parameters in providing quantitative insights, with α showing higher accuracy in estimating relative density. This work underscores the importance of localized calibration methods for penetrometer deployment in extraterrestrial environments, offering a framework for improved geotechnical analysis and operational success in future lunar and planetary missions.