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This article describes a comprehensive testing method for the thermal calibration of the Thermal InfraRed Sensor (TIRS) onboard NASA's Perseverance rover. Ground-based IR detectors operating at the surface of Mars are subjected to inaccuracies caused by the inclusion of thermal gradients in their packages. To reduce such uncertainties, it is necessary to compensate for their effects. Here, details of the TIRS thermo-mechanical design and a simplified thermal mathematical model (TMM) that accounts for the presence of thermal gradients in the detector's package are provided. Then, a set of equations for the estimation and compensation of thermal gradients are proposed based on the results of the TMM. Thermal calibration tests to identify the mathematical estimators are analyzed, providing details of the test setups and highlighting their limitations and restrictions. Finally, experimental results of the calibration tests are presented, along with the uncertainty sources and potential systematic errors associated with the estimation of the gradients. The results presented here show a significant improvement in the accuracy of TIRS versus previous work, thus fulfilling of the radiometer scientific requirements set by the Mars 2020 science team. • A new thermal calibration plan for a ground-based Martian IR radiometer. • Detectors package thermal gradients estimation based on thermal modeling and tests. • Simplified test setups and differences with the Martian environment. • Performance analysis accounting for test setup uncertainties and thermal modeling. • Uncertainties meet the scientific requirements stated by the Mars 2020 science team. [ABSTRACT FROM AUTHOR]

The Mars Environmental Dynamics Analyzer (MEDA) is a suite of environmental sensors onboard NASA’s Mars 2020 mission. The Thermal InfraRed Sensor (TIRS), developed at Centro de Astrobiología of Spain, is one of the six sensors comprising MEDA, and it will measure the net thermal infrared radiation and reflected solar radiation at the surface, as well as the atmospheric and surface skin temperatures using five different channels. In combination with MEDA's other sensors, TIRS will allow the quantification of the surface energy budget and the determination of key geophysical properties of the terrain such as the albedo and thermal inertia. Here we present a general description of the TIRS, its channels scientific requirements, and the mechanical and thermal design. Then, a detailed sensor mathematical model and a sensitivity analysis to model uncertainties are described. Some characterization test results to model parameters identification are included. Finally, accuracy and resolution calculus for each channel versus operational temperature is presented. The calculus is performed based on sensitivity equations, the practical tests results and the estimated values for different uncertainty sources. [ABSTRACT FROM AUTHOR]

• A new radiometric and angular calibration plan for a Martian IR radiometer. • Simplified test setups and differences with Martian environmental are described. • Spectral response analysis vs. radiation incidence angle and operational temperature. • Performance analysis accounting for calibration uncertainties and set-up limitations. • Uncertainties meet the scientific requirements stated by the Mars 2020 science team. This article describes a comprehensive testing method for the radiometric and angular calibration of the Thermal InfraRed Sensor (TIRS) onboard NASA's Mars 2020 mission. First, details of the TIRS opto-mechanical design, construction aspects of the IR detectors, and an update of the mathematical model used for the calculation of sensor internal IR fluxes are provided. Then, a set of sequential calibration tests to identify the radiometer model parameters are defined. The test setups are described, highlighting their limitations and restrictions based on differences between simulated and actual Martian environmental conditions. Finally, the uncertainty sources and potential systematic errors associated with the calibration tests are quantified and compared with the radiometer scientific requirements established by the Mars 2020 science team. [ABSTRACT FROM AUTHOR]