Autonomous Sensor System for Determining Instrument Position Relative to Unknown Surfaces Utilized on Mars Rover

In some applications, a robot arm has to position instrumentation/payloads accurately relative to an unknown surface. This article describes an optical sensor system for doing so. The sensor is based on a number of different image processing techniques combined with optical stimulation. More specifically, the system utilizes a camera, floodlight, structured light illumination, terrain relative navigation (TRN), camera pose estimation, and circle finding. The sensor has been developed for the Planetary Instrument for X-Ray Lithochemistry (PIXL) instrument on NASA’s Mars Perseverance rover. The sensor also has other applications such as exploration of polluted or inaccessible areas or locating a robotic arm relative to an unknown surface. The sensor can aid in placing an instrument relative to the unknown surface with an accuracy of 0.5 mm and maintaining a 3-D position lock utilizing TRN. This article will describe the sensor design and performance.