First observation of the Venus UV dayglow at limb from SPICAV/VEX



[1] We present the first limb observations of the dayglow emissions by the UV channel of SPICAV aboard Venus Express between October and December 2011. The CO Cameron bands between 180–260 nm and CO2+ doublet at 289 nm are clearly identified for the first time in the Venusian dayglow. The Cameron bands brightness peaks at 137.5 ± 1.5 km with a peak brightness of 2000 ± 100 kR and the CO2+ doublet peaks at 135.5 ± 2.5 km with a peak brightness of 270 ± 20 kR. The temperature near 145 km derived from the CO2+ bands scale height is 290 ± 60 K, in good agreement with other types of measurement. The spectral shape of the Cameron bands is similar to the spectral shape of the Cameron bands observed on Mars with the same coarse 10 nm resolution. The stronger brightness of the Venusian dayglow with respect to Mars dayglow in the 200–300 nm range cannot be explained only by the distance to the Sun and by the difference in EUV solar flux at the time of the observations.