Composition sensors calibration and characterization and warmup analysis for the Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE)

Abstract

MOXIE, the Mars Oxygen In-Situ Resource Utilization Experiment, is one of the payloads that is being carried on the Mars 2020 Perseverance rover. MOXIE was developed by MIT and NASA's Jet Propulsion Laboratory (JPL) to demonstrate, for the first time, In-Situ Resource Utilization (ISRU) on another planet by extracting O₂ from CO₂ in the Martian atmosphere using solid oxide electrolysis (SOE). In order to inform and control its system, MOXIE has a set of temperature, pressure, and composition sensors that measure its internal gas flows. The four composition sensors are commercial off-the-shelf (COTS) hardware and include an oxygen sensor (0 - 100%) and a carbon dioxide sensor (0 - 5%) for the output gas stream from the SOE anode (expected to be pure oxygen) and another carbon dioxide sensor (0 - 100%) and a carbon monoxide sensor (0 - 100%) for the cathode (a mixture of CO₂ and CO).

Except for the luminescence oxygen sensor, all of these composition sensors are Non-Dispersive Infrared Radiation (NDIR) sensors produced for Earth-ambient-conditions. The research presented in this thesis involves a series of tests under a range of temperatures, pressures and concentrations in order to properly calibrate and characterize (C&C) the sensors to understand their future behaviour on Mars prior to their flight on the Mars 2020 rover. In order to simulate Mars conditions and conduct the C&C tests, this research involved designing and constructing a temperature-controlled vacuum chamber. Following a set test plan, numerous sensor readings were recorded while varying the chamber gas composition, pressure and temperature.

The main motivation for this research is to extend the sensor manufacturer's results, which were designed for operation in stable terrestrial pressure and temperature regimes with frequent calibration, to a Martian environment with large dynamic pressure and temperature swings, variable ratios of gases with cross-sensitivity, and limited ability to calibrate in-situ. This research is critical in characterizing and calibrating the MOXIE sensors prior to their flight on the Mars 2020 rover, in order to be able to correctly interpret their readings. This thesis also covers the work on the thermal data processing and analysis of the warmup period of the heaters in MOXIE. It focuses on understanding the warmup duration, power and energy expenditure, and the heat loss models. This is critical both for planning operations on Mars and for analyzing the thermal control system and energy profiles.