Title: Radio Observation of Venus at Meter Wavelengths using the GMRT,
Abstract: The Venusian surface has been studied by measuring radar reflections and
thermal radio emission over a wide spectral region of several centimeters to
meter wavelengths from the Earth-based as well as orbiter platforms. The
radiometric observations, in the decimeter (dcm) wavelength regime showed a
decreasing trend in the observed brightness temperature (Tb) with increasing
wavelength. The thermal emission models available at present have not been able
to explain the radiometric observations at longer wavelength (dcm) to a
satisfactory level. This paper reports the first interferometric imaging
observations of Venus below 620 MHz. They were carried out at 606, 332.9 and
239.9 MHz using the Giant Meterwave Radio Telescope (GMRT). The Tb values
derived at the respective frequencies are 526 K, 409 K and < 426 K, with errors
of ~7% which are generally consistent with the reported Tb values at 608 MHz
and 430 MHz by previous investigators, but are much lower than those derived
from high-frequency observations at 1.38-22.46 GHz using the VLA.