Evaluation of the capability of ExoMars-TGO NOMAD infrared nadir channel for water ice clouds detection on Mars
Bibliographic record
Abstract
The Nadir and Occultation for Mars Discovery (NOMAD) is one of the four instruments on board the 2016 ExoMars Trace Gas Orbiter. The instrument is a suite of three spectrometers, mainly designed to study minor atmospheric species at high spectral resolution (A.C. Vandaele et al., 2015; E. Neefs et al., 2015). Nevertheless, Oliva et al. (2022) demonstrated the capability of NOMAD infrared nadir channel to investigate surface ice composition in the 2.3 – 2.6 μm wavelength range. Ice signatures have been also observed at mid/equatorial latitudes suggesting, after analysis, the first detection of CO2 ice clouds through the study of the narrow 2.35 μm absorption band. In this work, we also use observations of the NOMAD infrared LNO channel in order to evaluate its capability to detect H2O ice clouds. We present a technique taking advantage of the 2.7 µm strong ice absorption band. For this study, we select LNO spectral orders 167, 168, 169 and combine them to derive a spectral index for H2O ice detection, namely the Frost and Clouds Index (FCI). The acquisition of data during Mars Year 34 and 35 (March 2018 to February 2021) allows us to construct seasonal maps for H2O ice clouds. The results appear in agreement with previous studies focused on Mars Express SPICAM/UV and OMEGA data analysis (Willame et al., 2017; Olsen et al., 2021). FCI is sensitive to the Polar Hood clouds, although the full structure is not detected. Moreover, detections in the Aphelion Cloud Belt (ACB) are limited. This is consistent with previous OMEGA spectrometer observations (Olsen et al, 2021) showing different physical properties between the two main Martian atmospheric structures and making the ACB less detectable in the infrared. We hence derive the LNO channel sensitivity limit for these clouds detection. Acknowledgements ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (The Open University). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493), by Spanish Ministry of Science and Innovation (MCIU) and by European funds under grants PGC2018-101836-BI00 and ESP2017-87143-R (MINECO/FEDER), as well as by UK Space Agency through grants ST/V002295/1, ST/V005332/1 and ST/S00145X/1 and Italian Space Agency through grant 2018-2-HH.0. This work was supported by the Belgian Fonds de la Recherche Scientifique – FNRS under grant number 30442502 (ET_HOME). The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). US investigators were supported by the National Aeronautics and Space Administration. Canadian investigators were supported by the Canadian Space Agency. SR thanks BELSPO for the FED-tWIN funding (Prf-2019-077 - RT-MOLEXO). References A.C. Vandaele, et al., 2015. Optical and radiometric models of the NOMAD instrument part I: the UVIS channel. Optics Express, 23(23):30028–30042. Neefs, et al., 2015. NOMAD spectrometer on the ExoMars trace gas orbiter mission: part 1—design, manufacturing and testing of the infrared channels. Applied optics, 54(28):8494–8520. Oliva, F., et al., 2022. Martian CO2 Ice Observation at High Spectral Resolution With ExoMars/TGO NOMAD. Journal of Geophysical Research: Planets, 127, e2021JE007083. Willame, Y., et al., 2017. Retrieving cloud, dust and ozone abundances in the martian atmosphere using spicam/uv nadir spectra.Planetary and SpaceScience, 142:9–25. K.S. Olsen, et al., 2021 Retrieval of the water ice column and physical properties of water-ice clouds in the martian atmosphere using the OMEGA imaging spectrometer, Icarus, Volume 353, 2021, 113229, ISSN 0019-1035.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".