Mobile Manipulation of a Laser-induced Breakdown Spectrometer for Planetary Exploration

Abstract

Laser-induced Breakdown Spectrometry (LIBS) is an established analytical technique to measure the elemental composition of rocks and other matter on the Martian surface. We propose an autonomous in-contact sampling method based on an attachable LIBS instrument, designed to measure the composition of samples on the surface of planets and moons. The spectrometer module is picked up by our Lightweight Rover Unit (LRU) at the landing site and transported to the sampling location, where the manipulator establishes a solid contact between the instrument and the sample. The rover commands the instrument to trigger the measurement, which in turn releases a laser-pulse and captures the spectrum of the resulting plasma. The in-contact deployment ensures a suitable focus distance for the spectrometer, without a focusing system that would add to the instrument's volume and weight, and allows for flexible deployment of the instrument. The autonomous software computes all necessary manipulation operations on-board the rover and requires almost no supervision from mission control. We tested the LRU and the LIBS instrument at the moon analogue test site on Mt. Etna, Sicily and successfully demonstrated multiple LIBS measurements, in which the rover automatically deployed the instrument on a rock sample, recorded a measurement and sent the data to mission control, with sufficient quality to distinguish the major elements of the recorded sample.