Post launch spectral and radiometric performances of MAJIS, the VIS-NIR imaging spectrometer of JUICE
Abstract
The post-launch spectral and radiometric performances of MAJIS, the VISNIR imaging spectrometer of the ESA Jupiter Icy Moon Explorer (JUICE), have been evaluated using observations performed during the Lunar-Earth Gravitational Assist (LEGA) of 19–20 August 2024 and observations of the Internal Calibration Unit (ICU). Observations of the Earth provided a comprehensive check of the spectral performances taking advantage of narrow atmospheric absorption bands over the full wavelength range of MAJIS (0.5–5.56 µm). This was of particular interest for wavelengths larger than 3.5 µm due to limitations of the ground calibration setup in this wavelength range. The radiometric performance of MAJIS has been reassessed considering the updated spectral calibration and the comparison of ICU observations before and after launch. On this basis, the observations of the Earth and Moon by MAJIS were compared to that of other instruments. The very good agreement with atmospheric spectral features observed by Earth observation instruments validate the updated spectral calibration of MAJIS. Comparing radiances for the Earth is not straightforward due to the very specific photometric angles for MAJIS observations (phase ∼ 90°, “glint spot”) and the high time variability of cloud patterns. A good agreement has been obtained within these limitations and the MAJIS radiance evaluations for the Moon are also consistent with that obtained by instruments on lunar orbiters, which indicates that the post-launch absolute radiometric calibration of MAJIS is close to the mark. These comparisons benefited from the high quality of the MAJIS data obtained during the LEGA with a very high operability and a signal to noise ratio (SNR) up to 400 (more with stacking). Extrapolating the operating conditions at 1 AU to those at 5 AU confirm that MAJIS will obtain high quality data during the science operations phase around Jupiter.
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BibTeX
@article{langevin2026post,
title = {{Post launch spectral and radiometric performances of MAJIS, the VIS-NIR imaging spectrometer of JUICE}},
author = {Yves Langevin and Sébastien Rodriguez and Sandrine Guerlet and François Poulet and Giuseppe Piccioni and Livio Agostini and Raymond Armante and Emiliano d'Aversa and Gianrico Filacchione and Leigh Fletcher and Fabrizio Oliva and Clément Royer and Benoît Seignovert and Katrin Stephan and Federico Tosi and Tim Trent},
journal = {Annales Geophysicae},
year = {2026},
month = aug,
doi = {10.5194/angeo-44-825-2026},
url = {https://hal.science/hal-05753553v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Post launch spectral and radiometric performances of MAJIS, the VIS-NIR imaging spectrometer of JUICE
AU - Yves Langevin
AU - Sébastien Rodriguez
AU - Sandrine Guerlet
AU - François Poulet
AU - Giuseppe Piccioni
AU - Livio Agostini
AU - Raymond Armante
AU - Emiliano d'Aversa
AU - Gianrico Filacchione
AU - Leigh Fletcher
AU - Fabrizio Oliva
AU - Clément Royer
AU - Benoît Seignovert
AU - Katrin Stephan
AU - Federico Tosi
AU - Tim Trent
PY - 2026
DA - 2026/08/26
JO - Annales Geophysicae
DO - 10.5194/angeo-44-825-2026
UR - https://hal.science/hal-05753553v1
AB - The post-launch spectral and radiometric performances of MAJIS, the VISNIR imaging spectrometer of the ESA Jupiter Icy Moon Explorer (JUICE), have been evaluated using observations performed during the Lunar-Earth Gravitational Assist (LEGA) of 19–20 August 2024 and observations of the Internal Calibration Unit (ICU). Observations of the Earth provided a comprehensive check of the spectral performances taking advantage of narrow atmospheric absorption bands over the full wavelength range of MAJIS (0.5–5.56 µm). This was of particular interest for wavelengths larger than 3.5 µm due to limitations of the ground calibration setup in this wavelength range. The radiometric performance of MAJIS has been reassessed considering the updated spectral calibration and the comparison of ICU observations before and after launch. On this basis, the observations of the Earth and Moon by MAJIS were compared to that of other instruments. The very good agreement with atmospheric spectral features observed by Earth observation instruments validate the updated spectral calibration of MAJIS. Comparing radiances for the Earth is not straightforward due to the very specific photometric angles for MAJIS observations (phase ∼ 90°, “glint spot”) and the high time variability of cloud patterns. A good agreement has been obtained within these limitations and the MAJIS radiance evaluations for the Moon are also consistent with that obtained by instruments on lunar orbiters, which indicates that the post-launch absolute radiometric calibration of MAJIS is close to the mark. These comparisons benefited from the high quality of the MAJIS data obtained during the LEGA with a very high operability and a signal to noise ratio (SNR) up to 400 (more with stacking). Extrapolating the operating conditions at 1 AU to those at 5 AU confirm that MAJIS will obtain high quality data during the science operations phase around Jupiter.
SN - 0992-7689
SN - 1432-0576
ER -