Fig. 2.

Multi-wavelength remote sensing of Jupiter provides access to both reflected sunlight (UV to near-IR) and thermal emission (mid-IR to radio). These false-colour images demonstrate the appearance of the atmosphere at different wavelengths. JUICE UVS will measure scattered sunlight from upper-tropospheric aerosols. JANUS and MAJIS observations (below approximately 3 μm) sense clouds, chromophores and winds in the cloud decks using both the continuum and strong CH₄ absorption bands (Hueso et al. 2017; Grassi et al. 2020). MAJIS will be able to observe H₃⁺ emission from Jupiter’s ionosphere and auroras between 3-4 μm (VLT/ISAAC observations, Credit: ESO), as well as thermal emission from the deep cloud-forming layers (4-6 bars) near 5 μm (Gemini/NIRI observation, Wong et al. 2020). Although JUICE lacks mid-IR capabilities (VLT/VISIR observations sensing the upper troposphere at 0.1-0.5 bars, and stratosphere at 1-10 mbar, Fletcher et al. 2017a) and radio-wavelength capabilities (VLA observations, de Pater et al. 2016), sub-millimetre sounding by SWI will probe the stratospheric temperatures and winds. The approximate sensitivity of the JUICE instruments to different altitudes is shown in Fig. 26