Radiothermal Emission model of Venus

Abstract

The radio-thermal emission from Venus as observed by ground-based interferometric radio-telescopes shows a significant spectral variation, with a gradual increase in brightness temperature from 1 mm to 6 cm and a decrease thereafter at higher wavelengths. The first time GMRT observations beyond 70 cm wavelength also reconfirm this decreasing trend in Tb with the increase in wavelength [7]. Efforts have been made to model this spectral variation in Tb, [1], [10], but these models fail to explain the low-frequency radio-thermal emission from Venus (decrease in Tb with the increase in wavelength) and the problem still remains unresolved. The authors attempt to explain this problem using radiative transfer based model and radiometric observations of Venus focussing particularly on the higher wavelength Tb observations from the Giant meter radio telescope (GMRT). The GMRT brightness temperature (Tb) (at 0.21, 0.5, 0.9, 1.23 and 2 m) is observed to decrease with frequency. A radiative transfer model was developed and it is seen that a two layer Venusian surface model matches with the observations. Based on the simulation studies, the authors put forth a hypothesis that Venus may have an absorbing layer within the first few meter depth.