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Titan’s Twilight and Sunset Solar Illumination
摘要： We calculate the illumination conditions at Titan’s surface using the Monte Carlo radiative transfer model SRTC++, motivated by the proposed Dragon?y Titan lander. We ?nd signi?cant surface illumination during twilight after sunset, with the twilight ?ux maximized near 1.0 μm wavelength. Out to 30° past Titan’s terminator, the twilight illumination exceeds that of Earth’s Moon at full phase in visible red wavelengths (～0.65 μm). Imaging at night should be quite effective for stationary surface landers if they use long integration times, though it would be less effective for platforms ?oating on Titan’s seas. Titan sunsets should be underwhelming events at visible wavelengths, with the Sun fading out while still well above the horizon and overall illumination diminishing slowly as the Sun falls below the horizon. Shadows below the lander should receive illumination from diffusely scattered light low in the sky near Titan’s horizon. The total near-horizon illumination maximizes when the Sun is highest in the sky owing to the intensity of multiple scattering.
关键词： radiative transfer,planets and satellites: individual (Titan)
更新于2025-09-23 15:21:01
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EFFECTS OF NITROGEN PHOTOABSORPTION CROSS SECTION RESOLUTION ON MINOR SPECIES VERTICAL PROFILES IN TITAN’S UPPER ATMOSPHERE
摘要： The signi?cant variations in both measured and modeled densities of minor species in Titan’s atmosphere call for the evaluation of possible in?uencing factors in photochemical modeling. The effect of nitrogen photoabsorption cross section selection on the modeled vertical pro?les of minor species is analyzed here, with particular focus on C2H6 and HCN. Our results show a clear impact of cross sections used on all neutral and ion species studied. Affected species include neutrals and ions that are not primary photochemical products, including species that do not even contain nitrogen. The results indicate that photochemical models that employ low-resolution cross sections may signi?cantly miscalculate the vertical pro?les of minor species. Such differences are expected to have important implications for Titan’s overall atmospheric structure and chemistry.
关键词： planets and satellites: atmospheres,methods: numerical,atmospheric effects,planets and satellites: individual (Titan)
更新于2025-09-19 17:15:36