Polarization and brightness temperature observations of Venus with the GMRT

Venus was observed at frequencies of 1297.67 MHz (23 cm), 607.67 MHz (49 cm), and 233.67 MHz (1.28 m) with the Giant Metrewave Radio Telescope (GMRT) during the period of 2015 July 25 and September 6 when it was close to its inferior conjunction. Values of the brightness temperature (Tb) of Venus from these observations were derived as 622 ± 43 K, 554 ± 38 K for 1297.67 and 607.67 MHz frequencies, respectively, which are in agreement with the previous observations. The attempt to derive the Tb at 233.67 MHz affirms an upper limit of 321 K which is significantly lower than the previously reported upper limit of 426 K at the same frequency. We also present the dielectric constant (ε) values of the Venus surface estimated using the degree of polarization maps of Venus, derived from the GMRT polarization observations and theoretical calculations. The ε of the Venus surface was estimated to be ∼4.5 at both the 607.67 and 1297.67 MHz, close to the reported values of ε of 4 to 4.5 from the radar-based observations including the Magellan observations at 2.38 GHz (12.6 cm).