The MEDA Thermal IR Radiometer (TIRS) for the Mars 2020 Mission

E. Sebastián1, G. M. Martínez2,3, M. Ramos4, F. Haenschke5, M. Fernández1, R. Ferrándiz1, M. de la Torre-Juárez6 and J. A. Manfredi1 1Centro de Astrobiología (CSIC-INTA), Torrejón de Ardoz, Madrid, Spain, ([email protected]), 2Lunar and Planetary Institute, Universities Space Research Association, Houston, TX, USA, 3University of Michigan, Ann Arbor, MI, USA, 4Departamento Física y Matemáticas, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain, 5Institute of Photonic Technology, Jena, Germany, 6Jet Propulsion Laboratory-Caltech, Pasadena, USA.

Introduction Instrument General Description Mechanical Description The Thermal Infrared Sensor (TIRS) is one of the six environmental sensors The TIRS’ sensor head: • The housing and covers provide a mechanical chassis that attaches to comprising the Mars Environmental Dynamics Analyzer (MEDA), which in • Located at 1.5 m height in the rover’s RSM the rover RSM and thermally isolates and protects IR detectors from the turn is one of the seven scientific instruments onboard the NASA Mars • Weight of 97 g and size of 58×63×58 mm Martian environment. 2020 rover. • The support plate is essentially a thermal stabilization system for The electronic conditioning system: minimizing the appearance of thermopiles’ package thermal gradients. MEDA [1] is provided by the Spanish • Located in the MEDA’s Instrument Control Unit • The calibration plate has small holes partially obstructing the Centro de Astrobiología and has been • Connected through a ∼3–4 m long harness thermopiles’ FoV to conform the target FoV, protects the thermopiles designed to characterize the near- Downward-looking channels FoV optics from dust deposition, and allows inflight recalibrations. For this surface climate of Mars and prepare (3-4 m2) at of 3.75 m away from last purpose, the support and calibration plates include contact for human exploration by assessing IR transducers orientation and FoV comply with: RTG footprint center temperature sensors and heaters that are activated during the process. the environmental conditions across • The FoV does not intersect with any rover’s element the rover traverse. • The focused area is small enough to minimize heterogeneities in the soil composition/texture, but big enough to have a proper signal to TIRS [2] is the first in-situ Martian noise ratio infrared (IR) radiometer including • Minimize the thermal influence of the Mars 2020 rover Radioisotope upward- and downward-looking Thermoelectric Generator (RTG) channels, complementing and extending radiometric measurements IR Detectors 3 of REMS-MSL and HP -Insight [3]. Thermopiles TS-100 from the TIRS exploded 3D drawing Leibniz IPHT (Institute of Photonic Expected performance Technology, Jena, Germany) Scientific Objectives Accuracy and resolution of TIRS’ channels obtained from: TIRS will provide surface weather TIRS mounted on Mars2020 rover RSM TIRS thermopile package. Stain-steel socket and • The calibration results of the TIRS FM measurements which, in combination (black arrow; credit: NASA/JPL-Caltech) Filters’ transmission bands thermopile chip (Credit IPHT), Thermopile filter • Uncertainties of calibration test set-ups with the MEDA Radiation and Dust selected to fulfill the science glued to the nickel cap • Electronic measurement errors Sensor’s panchromatic channel goals for each channel Channel Band(mm) Filter Substrate Absorber Fillgass • In-flight calibration algorithm performance (downward SW radiation), can be IR1 6.5–30 Si IF LW • Thermal gradients in thermopiles packages used to: Interferometric absorbers (IF LW) IR2 14.5–15.5 Ge IF LW • Detectors ageing to avoid undesired transparent • Validate global atmospheric model IR3 0.3–3 Quartz BS Krypton windows for Silicon filters at IR4 6.5–30 Si IF LW Specular reflection of the solar Channel Dynamic range Accuracy1 Resolution • Quantify the surface energy budget [4] 2 twice the bandpass or and for IR5 8–14 Si IF LW radiation within the FoV of the IR1 [W/m ] 3.5-180 ±1.7 to 6.2 ±0.18 • Determine soil albedo and thermal inertia IR2[K] ±3.7 ±0.45 Germanium above 40–50 μm TIRS IR3 is expected to cause 173-293 at spatial scales of a few m2 IF LW (Interferometric LongWave), SB (black silver) IR3[W/m2] 0-230 ±3.7 to 9.5 ±0.1 spurious overestimations in IR4[W/m2] 50-420 ±1.2 to 3 ±0.1 Channel Purpose FoV Pointing angles measured reflected solar fluxes. IR5[K] 173-293 ±0.7 ±0.08 1 IR1 Downward LW Upward(+35°) Variation depends on thermal scenario (diurnal and Position and relative orientation seasonal variation). IR2 Atmos. Temp Upward(+35°) TIRS flight model Horizontal ±20º between the TIRS and the Sun, as IR3 Upward SW Downward(-35°) Current best estimate of the TIRS channels Vertical ±10º IR4 Upward LW Downward(-35°) well as the optical properties of performance (1s error) IR5 Ground Temp Downward(-35°) the terrain need to be considered. The direct incidence of the Sun on the detector's optics of the upward Measuring: looking channels IR1 and IR2 imposes limitations in their performance. • The net thermal infraredand reflected solar radiation at the surface Specifically, heating of frontal elements of the detectors may result in • The surface brightness temperature, and the near-surface vertical measurement errors that need to be properly assessed. temperature profile Calibrated spectral responsivity of TIRS channels, multiplying the filter transmission characteristics by the corresponding absorber Channel IR5 has been calibrated for measuring bigness temperature (assuming a broadband LW surface emissivity of 1). The uncertainty in References: [1] Rodriguez-Manfredi, J. A., et al. (2014), MEDA: an environmental and kinematic temperature determination <3 K at typical maximum ground meteorological package for Mars 2020, LPSC, 45. [2] Pérez-Izquierdo, J., et al. (2018), The temperatures of ~ 273 K and emissivities of ~0.96. Thermal Infrared Sensor of the Mars Environmental Dynamics Analyzer instrument onboard Mars 2020, a general description and performance analysis, Measurement, 122, 432-442. [3] Acknowledgments: MEDA/TIRS was designed and built with funding from the Instituto Sebastián, E. et al. (2010), The Rover Environmental Monitoring Station Ground Temperature Nacional de Técnica Aeroespacial (INTA); Plan Estatal de I+D+I [ESP2014-54256-C4-1-R, Sensor: A Pyrometer for Measuring Ground Temperature on Mars, Sensors, 10, 9211-9231. ESP2015-68281-C4-1-R, ESP2016-79612-C3-1-R,FIS2016-77578-R, RTI2018-099825-B-C31 and [4] Martínez, G. M., et al. (2014), Surface energy budget and thermal inertia at Gale Crater: MDM-2017-0737]; the CDTI and Jet Propulsion Laboratory [subcontract 1515850]. GM Calculations from ground-based measurements, JGR: Planets 119.8: 1822-1838. Martínez wishes to acknowledge funding from JPL [Sub. No. 1638782].