the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Humidity Measurements in Carbon Dioxide with Sensirion SHT85 Humidity Sensors under simulated Martian atmospheric conditions
Abstract. Humidity sensors that function under extreme conditions are needed in experimental chambers in which the atmospheric conditions near the surface of Mars are simulated, as well as for in-situ measurements of humidity on the surface of Mars. Experimental setups with such sensors have already been constructed at the German Aerospace Center (DLR) and published. However, the SHT75 sensors from Sensirion used at that time are no longer in production and have been replaced by a new generation of sensors: SHT85. The SHT85 sensors are more precise than their predecessors, have a new sensor chip, and feature a PTFE membrane over the humidity-sensitive layer to protect the sensor from dust and liquids. The data interface to the I2C bus has also changed. Due to these significant changes, it was necessary to verify the sensor’s capabilities under extreme conditions. For this purpose, the sensors were tested under the same conditions and in parallel to the calibration of the MEDA HS sensor from the Finnish Meteorological Institute (FMI), onboard NASA's Mars 2020 rover. The results show that the SHT85 is, as its predecessor SHT75, suitable for measurements under Martian atmospheric conditions when the relative humidity is in the range >5 %.
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Status: open (until 21 Feb 2025)
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RC1: 'Comment on egusphere-2024-3944', Anonymous Referee #1, 28 Jan 2025
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The manuscript describes a new humidity measurement performance in conditions expected on Mars surface. It is clear, rigorous and well written.
The main limitation of the current manuscript is the limited discussion over weird behavior observed at 6 hPa, the hypothesis seems reasonable so the manuscript could improve from detailing the underlying reasons and limitations.Citation: https://doi.org/10.5194/egusphere-2024-3944-RC1 -
AC1: 'Reply on RC1', Andreas Lorek, 03 Feb 2025
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This weird behavior occurred at 6 hPa (-60°C) and at 8 hPa (-70°C). Both times after decreasing the temperature and starting the new measurement campaign for different pressures. The cause could be e.g. a time lag in the adaptation of the polymer to the new conditions (desorption of molecules or a phase change from water to ice) or a time lag in the adaption of the electronics inside the SHT85.
The paper can be expanded with these sentences to indicate the possible causes.
In the future, measurements at temperatures less than -50°C have to be scrutinized for this behavior with a view to finding the causes.
Citation: https://doi.org/10.5194/egusphere-2024-3944-AC1 -
RC2: 'Reply on AC1', Anonymous Referee #1, 03 Feb 2025
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Thank you for the details.Â
I would recommend adding these sentences to the manuscript.Citation: https://doi.org/10.5194/egusphere-2024-3944-RC2 -
AC2: 'Reply on RC2', Andreas Lorek, 06 Feb 2025
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Yes, we will add the sentences.
Citation: https://doi.org/10.5194/egusphere-2024-3944-AC2
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AC2: 'Reply on RC2', Andreas Lorek, 06 Feb 2025
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RC2: 'Reply on AC1', Anonymous Referee #1, 03 Feb 2025
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AC1: 'Reply on RC1', Andreas Lorek, 03 Feb 2025
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