The MAJIS / JUICE odyssey
The JUICE satellite will thoroughly explore the Jovian system. One of its instruments, MAJIS, is developed through the scientific responsibility of the Institut d'Astrophysique Spatiale (IAS, France). It consists of a two channels hyperspectral imager (VIS-NIR and IR) covering the 0.5 µm to 5.54 µm range. This instrument is essential to the mission since it will contribute to the study of Jupiter's atmosphere and to the characterization of the surfaces of its icy moons.
Before the launch, the detectors must be characterized in order to guarantee an optimized processing of the raw signals collected during the mission, and thus convert them into quality scientific data. The role of the Royal Belgian Institute for Space Aeronomy, in collaboration with the Royal Observatory of Belgium, was to develop a dedicated bench in thermal vacuum and radiometry in order to characterize both the flight and the spare model of the VIS-NIR detector.
The VIS-NIR calibration unit
This bench mainly consists of a vacuum chamber coupled to a cryostat to simulate space (especially Jupiter) environment and reach temperatures from 95 K to 160 K. To illuminate the detector (through a window), key equipment essentially composed of a light source, a double monochromator and an integrating sphere is available.
In this way, the MAJIS detector integrated in the chamber in a protective mount (Figure 1) receives a stable, homogeneous, and monochromatic luminous flux, adjustable in wavelength and intensity. Calibrated photodiodes are used to calibrate the optical power reaching the detector. Software and a security system, fully developed at BIRA-IASB, ensure the bench automation and detector integrity.
The characterization campaign
The MAJIS VIS-NIR flight model detector (Figure 2) was characterized in 2020 under supervision of B.USOC. This campaign allowed the successful study of the intrinsic properties of the detector (dark conditions), as well as its response to a well-characterized illumination flux such as the homogeneity of its inter-pixel response, the linearity, spectral response (quantum efficiency), saturation level, persistence and various properties of its proximity electronics (gain, noise, bias).
Reference
Bolsée, D., Van Laeken, L., Cisneros-González, M.E., Pereira, N., Depiesse, C., Jacobs, L., Vandaele, A.C., Ritter, B., Gissot, S., Karatekin, Ö. Poulet, F., Langevin, Y., Dumesnil, C., Dubois, J.-P., Arondel, A., Haffoud, P., Ketchazo, C., and Hervier, V. (2020). Characterization facility for the MAJIS/JUICE VIS-NIR FM and SM detectors. Proceedings of SPIE 11443: Space Telescopes and Instrumentation 2020: Optical, Infrared, and Millimeter Wave, SPIE Astronomical Telescopes + Instrumentation, 14-18 December 2020, 1214-1233. https://doi.org/10.1117/12.2576319
