The near-infrared spectrum of Venus’ nightside is opacity-dominated, but Venusian atmosphere is transparent at some windows, as 1.0 mm, 1.10 mm, 1.18 mm, 1.27 mm and 1.31 mm. Emission in the 1.0 mm window come principally from surface; in the 1.10 mm and 1.18 mm surface contribution is 40-50%; in the 1.27 mm window emission come from air glow, while in the 1.31 mm window emission is only atmospheric.

VIRTIS is an imaging spectrometer in Venus Express spacecraft. The work is an attempt to extract useful information from Venus surface by remote sensing measurements. We used VIRTIS-M IR and Magellan data.

Our analysis is focused on the 1.0 mm window: comparing observed spectra with synthetic spectra (provided by a Venusian atmosphere model, developed by C. Tsang), it’s possible to retrieve surface emissivity. In fact, spectrum slope between 1.03 and 1.04 mm wavelengths is directly proportional to emissivity and cube surface temperature. So, if we have a lapse rate estimate and a topographic map, we can know surface temperature in every region of planet’s nightside, and then it’! s possible to retrieve emissivity.