Preprints
https://doi.org/10.5194/egusphere-2023-1823
https://doi.org/10.5194/egusphere-2023-1823
17 Aug 2023
 | 17 Aug 2023
Status: this preprint is open for discussion.

Improving relative humidity measurements on Mars: New laboratory calibration measurements

Maria Hieta, Iina Jaakonaho, Jouni Polkko, Andreas Lorek, Stephen Garland, Jean-Pierre de Vera, Maria Genzer, and Ari-Matti Harri

Abstract. In this paper we present new calibration measurements that have been performed with the ground reference models of the relative humidity instruments of the MSL, Mars 2020 and ExoMars missions. All instruments are based on capacitive sensor head technology, and they are developed, manufactured and tested by The Finnish Meteorological Institute (FMI). Calibration of capacitive humidity sensors for the Martian environment has been a challenging task and special facilities are needed in order to create Martian conditions including all relevant environmental parameters: low pressure, low temperature, carbon dioxide environment, and especially humidity that can be accurately controlled and measured. A measurement campaign was performed at DLR PASLAB (Planetary Analog Simulation Laboratory) determining relative humidity calibration data sets for REMS-H, MEDA HS and METEO-H instruments in temperatures from -30 °C down to -70 °C in low pressure CO2. In addition to the stable point humidity calibration measurements in CO2, the instrument performance was tested with the actual Martian atmosphere composition, and during long continuous measurements. The new calibration data set has already been used in the flight calibration of the MEDA HS instrument resulting in successful calibration and excellent accuracy. The results from this campaign will further improve relative humidity measurements on Mars by providing the means to reanalyse the current calibration of the REMS-H flight model, and by allowing more accurate comparison between the two instruments currently on the Martian surface.

Maria Hieta, Iina Jaakonaho, Jouni Polkko, Andreas Lorek, Stephen Garland, Jean-Pierre de Vera, Maria Genzer, and Ari-Matti Harri

Status: open (extended)

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Maria Hieta, Iina Jaakonaho, Jouni Polkko, Andreas Lorek, Stephen Garland, Jean-Pierre de Vera, Maria Genzer, and Ari-Matti Harri
Maria Hieta, Iina Jaakonaho, Jouni Polkko, Andreas Lorek, Stephen Garland, Jean-Pierre de Vera, Maria Genzer, and Ari-Matti Harri

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Short summary
This paper describes new humidity measurements that have been performed with the humidity instruments of the MSL, Mars 2020 and ExoMars missions. Special facilities are needed in order to create Martian conditions and a measurement campaign was performed at DLR to obtain data sets for REMS-H, MEDA HS and METEO-H instruments. The results from this campaign have improved the humidity data we receive from MEDA HS/Perseverance, and it can further improve the existing Martian relative humidity data.