Scientific goals and technical challenges of the MAJIS imaging spectrometer for the JUICE mission

The MAJIS (Moons And Jupiter Imaging Spectrometer) instrument on board the ESA JUICE (JUpiter ICy moon Explorer) mission is an imaging spectrometer operating in the VIS-NIR spectral range from 0.50 to 5.54 μm. The scientific objectives of MAJIS span from a comprehensive study of the icy satellites, with particular emphasis on Ganymede, to the Jupiter atmosphere, including its aurorae. Additional complementary science can be addressed for the Jupiter' ring, the active satellite Io and eventually some irregular satellites, providing an important set to increase the knowledge of the whole Jupiter system, sometime referred to as a miniature solar system. The accurate measurement of radiance from the different targets, in some case particularly faint due to strong absorption features in contrast to possible high thermal background, require a cryogenic instrument operating in a severe radiation environment, with very limited power from the solar cell requiring a passive cooling. All elements translate into significant challenges in the design, qualification and testing of the instrument. In this paper we report the scientific objectives and briefly discuss the outline design of the MAJIS optical head.