Evaluation of the wavelength distortion model and its accuracy. Left panel: Spectra of Saturn from 80 different locations throughout the Ch3B FOV plotted as a function of wavelength using the FLT-4 and FLT-5 wavelength solutions; note how FLT-5 resolves wavelength calibration artifacts seen for some locations. Right panel: Wavelength offset as a function of wavelength of the FLT-4 (black solid lines) and FLT-5 (red dashed lines) spectra against the atmospheric models produced using radiative transfer code NEMESIS for three arbitrarily selected positions within the Ch 3B FOV. Solid black squares represent the locations of the HI 17−10, HI 13−9, HI 16−10, and [NeIII] λ15.5551 µm features used to constrain the FLT-4 models from NGC 6543.