Impact of gradients at the Martian terminator on the retrieval of ozone from TGO/NOMAD-UVIS

Autor: Arianna Piccialli, Ann Carine Vandaele, Lori Neary, Yannick Willame, Shohei Aoki, Loic Trompet, Cedric Depiesse, Sebastian Viscardy, Frank Daerden, Justin Erwin, Ian R. Thomas, Bojan Ristic, Jon P. Mason, Manish Patel, Alain Khayat, Mike Wolff, Giancarlo Bellucci, Jose Juan Lopez-Moreno
Rok vydání: 2022
Popis: We will investigate the impact of day-night temperature and compositional gradients at the Martian terminator on the retrieval of vertical profiles of ozone obtained from NOMAD-UVIS solar occultations. Rapid variations in species concentration at the terminator have the potential to cause asymmetries in the species distributions along the line of sight of a solar occultation experiment. Ozone, in particular, displays steep gradients across the terminator of Mars due to photolysis [1]. Nowadays, most of the retrieval algorithms for solar and stellar occultations rely on the assumption of a spherically symmetrical atmosphere. However, photo-chemically induced variations near sunrise/sunset conditions need to be taken into account in the retrieval process in order to prevent inaccuracies.NOMAD (Nadir and Occultation for MArs Discovery) is a spectrometer composed of 3 channels: 1) a solar occultation channel (SO) operating in the infrared (2.3-4.3 μm); 2) a second infrared channel LNO (2.3-3.8 μm) capable of doing nadir, as well as solar occultation and limb; and 3) an ultraviolet/visible channel UVIS (200-650 nm) that can work in the three observation modes [2,3]. The UVIS channel has a spectral resolution ozone and aerosols [4,5,6].Since the beginning of operations, on 21 April 2018, NOMAD-UVIS acquired more than 8000 solar occultations with an almost complete coverage of the planet.NOMAD-UVIS spectra are simulated using the line-by-line radiative transfer code ASIMUT-ALVL developed at IASB-BIRA [7]. In a preliminary study based on SPICAM-UV solar occultations (see [8]), ASIMUT was modified to take into account the atmospheric composition and structure at the day-night terminator. As input for ASIMUT, we used gradients predicted by the 3D GEM-Mars v4 Global Circulation Model (GCM) [9,10]. References[1] Lefèvre, F., Bertaux, J.L., Clancy, R. T., Encrenaz, T., Fast, K., Forget, F., Lebonnois, S., Montmessin, F., Perrier, S., Aug. 2008. Heterogeneous chemistry in the atmosphere of Mars. Nature 454, 971–975.[2] Vandaele, A.C., et al., Planetary and Space Science, Vol. 119, pp. 233–249, 2015. [3] Neefs, E., et al., Applied Optics, Vol. 54 (28), pp. 8494-8520, 2015.[4] M.R. Patel et al., In: Appl. Opt. 56.10 (2017), pp. 2771–2782. DOI: 10.1364/AO.56.002771. [5] M.R. Patel et al., In: JGR (Planets), Vol. 126, Is. 11, 2021.[6] Khayat, Alain S. J., et al., In: JGR (Planets), Vol. 126, Is. 11, 2021.[7] Vandaele, A.C., et al., JGR, 2008. 113 doi:10.1029/2008JE003140.[8] Piccialli, A., Icarus, submitted.[9] Neary, L., and F. Daerden (2018), Icarus, 300, 458–476, doi:10.1016/j.icarus.2017.09.028.[10] Daerden et al., 2019, Icarus 326, https://doi.org/10.1016/j.icarus.2019.02.030
Databáze: OpenAIRE