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Expected performances of MIST-A onboard EMA: inputs from surface spectrophotometric and thermal models

Presentation #118.04 in the session Mission-supporting Practices, Modeling, and Data (Poster + Lightning Talk)

Published onOct 23, 2023
Expected performances of MIST-A onboard EMA: inputs from surface spectrophotometric and thermal models

The Emirates Mission to the Asteroid belt (EMA, scheduled to launch in March 2028) will fly-by six main belt asteroids from 2030 to 2033, and finally rendezvous with asteroid (269) Justitia in 2034 [1]. The mission scientific payload consists of four remote sensing instruments, among which the MWIR Imaging Spectrometer for Target-Asteroids (MIST-A, [2]), designed to acquire hyperspectral images of the seven asteroids and characterize their composition and thermal properties. MIST-A will operate in the 2-5 µm spectral range with a sampling of <10 nm/band, thus allowing to 1) characterize the surface distribution of the spectral signatures of various classes of relevant compounds for primitive targets, such as aromatic (at 3.3 µm) and aliphatic organics (3.4-3.5 µm) [3], carbonates (3.5 µm, 4.0 µm) [4, 5], phyllosilicates (2.7 µm) [4, 5], ammonium salts (2.2 µm, 3.1-3.3 µm) [6, 7] and water ice (3 µm) [8, 9], and 2) measure the surface thermal emission longward of 3 µm.

Here we characterize the performances of MIST-A by means of simulations of the radiance from the mission targets. To this aim we produce spectrophotometric models (e.g. [10]) to compute the surface spectral reflectance as a function of observation geometry and composition. As input for the proposed simulations, we take advantage of already available spectrophotometric models of the surface of primitive bodies [11], spectral data from telescopic [12] and space-borne facilities, laboratory spectral reflectance measurements, and optical constants of endmembers of interest. We explore the effects on the spectral radiance of varying endmember abundances, grain size and mixing modalities, and, by including the contribution of thermal emission, of the surface temperature. Such simulations will be used as input for the MIST-A radiometric model to provide SNR estimations and detectability thresholds of the investigated compounds. The results of this work will support the observation planning for the different mission phases.

Funding of EMA is provided by UAESA. Funding for the MIST-A instrument is provided by ASI.

[1] Al Mazmi et al., ACM 2023; [2] Filacchione et al., ACM 2023; [3] Raponi et al., 2020, Nat. Astron., 4, 500-505; [4] De Sanctis et al., 2015, Nature 528, 241–244; [5] Kaplan et al., 2020, Science, 370, eabc3557; [6] De Sanctis et al., 2016, Nature 536, 54–57; [7] Poch et al., 2020, Science, 367, aaw7462; [8] Ciarniello et al., 2022, Nat. Astron., 6, 546-553; [9] Raponi et al., 2018, Sci. Adv., 4, id. eaao3757; [10] Hapke, 2012, Cambridge Univ. Press; [11] Ciarniello et al., 2017, A&A, 598, A130; [12] Hasegawa et al., 2021, ApJ L., 916, L6.

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