New high-resolution solar spectrum in the 0.7-1.7 µm domain obtained with the ACS-NIR spectrometer (TGO)

Abdanour Irbah; Jean-Loup Bertaux; Franck Montmessin; Alexander Trokhimovskiy; Oleg Korablev; Anna Fedorova

doi:10.1117/12.3018701

23 August 2024 New high-resolution solar spectrum in the 0.7-1.7 μm domain obtained with the ACS-NIR spectrometer (TGO)

Abdanour Irbah, Jean-Loup Bertaux, Franck Montmessin, Alexander Trokhimovskiy, Oleg Korablev, Anna Fedorova

Proceedings Volume 13092, Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave; 130927E (2024) https://doi.org/10.1117/12.3018701
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Abstract

The infrared solar spectrum measured from the ground is difficult, if not impossible, outside the observation windows permitted by the Earth’s atmosphere. Existing solutions then call on modelling of the Sun, correction of ground measurements of atmospheric transmission or even measurements from space. This latter opportunity was seized with infrared observations from the Trace Gas Orbiter (TGO) interplanetary probe orbiting MARS launched to study its atmosphere using spectrometers installed on its Atmospheric Chemistry Suite (ACS) platform. The spectrometer ACS-NIR (Near InfraRed) thus makes it possible to probe the Martian atmosphere in the 0.7-1.7 μm spectral domain thanks to its solar occultation mode. In this mode, the ACS-NIR is pointed toward the Sun and its line of sight gradually passes through MARS’ atmosphere as the satellite moves in its orbit. The high-resolution solar spectrum is directly measured when the line of sight is above the atmosphere. A 10-month observation plan (October 2020-August 2021) consisting of recording all diffraction orders from the ACS-NIR was specifically deployed for this objective. One of the main concerns we face when recovering the solar spectrum is spectral contamination of diffraction orders. We will first present how we processed the diffraction order images to obtain the best possible solar spectrum in the 0.7-1.7 μm band. We will show how the use of 3 off-centre images of the same diffraction order allows both to avoid spectral contamination and to improve the detection of solar lines at the ends of the order image where the intensity is low. We will then show the final version of the solar spectrum that we obtain which will be compared to the Toon spectrum taken as a reference. We will finish by addressing the parts of the spectrum which present solar lines located in spectral bands not observable from Earth and absent from the reference spectrum.

Citation Download Citation

Abdanour Irbah, Jean-Loup Bertaux, Franck Montmessin, Alexander Trokhimovskiy, Oleg Korablev, and Anna Fedorova "New high-resolution solar spectrum in the 0.7-1.7 μm domain obtained with the ACS-NIR spectrometer (TGO)", Proc. SPIE 13092, Space Telescopes and Instrumentation 2024: Optical, Infrared, and Millimeter Wave, 130927E (23 August 2024); https://doi.org/10.1117/12.3018701

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