Improving relative humidity measurements on Mars:  new laboratory calibration measurements

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

doi:https://doi.org/10.5194/gi-13-337-2024

Articles | Volume 13, issue 2

https://doi.org/10.5194/gi-13-337-2024

© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/gi-13-337-2024

© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 13, issue 2

Research article

|

18 Nov 2024

Research article |

| 18 Nov 2024

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

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Final revised paper (published on 18 Nov 2024)
Preprint (discussion started on 17 Aug 2023)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2023-1823', Andrew Ball, 04 Apr 2024

The paper is a welcome contribution to the understanding of humidity measurements on Mars.
Only minor comments:
1) Perhaps add a global plot of predicted vs. measured RH values for the new overall calibration approach, showing the remaining residuals.
2) Comment on whether or not any hysteresis effect is observed.
3) Does the work suggest any recommendations for accommodation, calibration or operation of such sensors on future missions?

Citation: https://doi.org/10.5194/egusphere-2023-1823-RC1
- AC1: 'Reply on RC1', Maria Hieta, 16 Sep 2024
  
  Thank you for reviewing our manuscript and for the comments and suggestions. Responses to the comments are provided below:
  1) Residual plots have been left out from this manuscript since they are provided in related calibration papers in preparation by Tabandeh and Hieta.
  2) In general, the calibration measurements were performed both in increasing and decreasing humidity. It can be seen in the capacitance plots that there are some differences between the measurements at the same humidity, but differences are not consistent and might be due to changing test environment (temperature or pressure drifting). If hysteresis were present, it would be smaller than the other uncertainties involved in the measurements.
  3) Calibrating the sensors in a representative operating environment, accounting for all factors affecting their performance, is crucial and has now been demonstrated to be feasible. A ground reference model can be used to transfer calibration information to the flight model, provided the test campaign is carefully planned and the models are sufficiently identical, and it has also been demonstrated that this approach is effective.
  
  Citation: https://doi.org/10.5194/egusphere-2023-1823-AC1
RC2: 'Comment on egusphere-2023-1823', Anonymous Referee #2, 11 Sep 2024

This paper describes a detailed calibration and characterisation campaign under proper Marian environmental conditions, of representative ground reference models of three humidity sensors landed on Mars. Two of these are still in operation on Mars (on Curiosity and on Perseverance). These sensors had not been subjected to a thorough calibration campaign before their launches, partly due to the complexity and difficulties to realise such calibrations. This paper provides a detailed description of the calibration campaign and the related results. The paper is well written, well referenced, the figures are clear and representative. The paper is recommended for publication as is.

Citation: https://doi.org/10.5194/egusphere-2023-1823-RC2

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload

AR by Maria Hieta on behalf of the Authors (16 Sep 2024) Author's response Author's tracked changes Manuscript

ED: Publish as is (29 Sep 2024) by Ralf Srama

AR by Maria Hieta on behalf of the Authors (30 Sep 2024) Manuscript

Short summary

This paper describes new humidity measurements performed with the humidity instruments of the MSL, Mars 2020 and ExoMars missions. Special facilities are needed to create Martian conditions, and a measurement campaign was performed at the German Aerospace Center (DLR) to obtain datasets for REMS-H, MEDA HS and METEO-H instruments. The results from the campaign improved the humidity data we receive from MEDA HS/Perseverance and can further improve the existing Martian relative humidity data.