The SuperCam infrared instrument on the NASA MARS2020 mission: performance and qualification results
Résumé
In July 2020, NASA will launch the Mars2020 mission. This mission, very similar to the Mars Science Laboratory and its rover Curiosity, consists in landing an instrumented rover on the Martian surface in order to characterize the geology and history of a new landing site on Mars, investigate Mars habitability, seek potential biosignatures, cache samples for an eventual return to Earth, and demonstrate in-situ production of oxygen needed for human exploration.
The rover will carry several different instruments to perform field analyses in biology, climatology, mineralogy, geology and geochemistry. Among this payload, the SuperCam instrument, an improved new generation of the ChemCam instrument on Curiosity, has been developed for remote microscale characterization of the mineralogy and elemental chemistry of the Mars surface, along with the search for extant organic materials. In addition to the elemental characterization offered by Laser-Induced Breakdown Spectroscopy (LIBS), a new remote Raman spectroscopy analysis and an infrared spectrometer have been added for a complete mineralogical and chemical characterization of the samples. A context color imaging capability is also implemented to place the analyzed samples in their geological context.
SuperCam consists of three units. The “Body Unit” built by the LANL (Los Alamos National Laboratories) in the US, the “Mast Unit” built by a French consortium of 5 laboratories (IRAP as leader, LESIA, LATMOS, IAS, and LAB) funded by the French Space Agency (CNES), and a “Calibration Target Unit“ under the responsibility of the University of Valladolid in Spain.
A very compact IRS (Infrared Spectrometer) is part of the SuperCam-MU payload. The IRS concept is based on the spectral selection by an Acousto-Optic Tunable Filter (AOTF) in the 1.3-2.6 μm range with a spectral resolution better than 30 wavenumbers. The AOTF is driven by radio frequencies injected in a transducer mounted directly on a birefringent crystal. This coupling creates acoustic waves in the crystal that behave like a Bragg grating. The incident light is then diffracted in two orders (e-ray and o-ray) at the same wavelength following a so-called tuning relation law (relation between diffracted wavelength and injected radio frequency). Each diffracted order is focused on a photodiode. A complete spectrum is obtained after the scan of all individual wavelengths.
The IRS is built by LESIA and LATMOS, two French laboratories located in Paris area.
After intensive performance and qualification tests as well as a calibration on a flight-representative model, the team has built the flight model. The qualification results and the performances of the instrument are presented.
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