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 25th July and 6th September 2015 when it was close to its inferior conjunction .
Values of the brightness temperature ( \textit { T } _ { \textup { b } } ) of Venus from these observations were derived as 622 \pm 43 K , 554 \pm 38 K for 1297.67 and 607.67 MHz frequencies , respectively , are in agreement with the previous observations .
The attempt to derive the \textit { T } _ { \textup { b } } 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 ( \varepsilon ) values of the Venus surface estimated using the degree of polarisation maps of Venus , derived from the GMRT polarisation observations and theoretical calculations .
The \varepsilon of the Venus surface was estimated to be \sim 4.5 at both the 607.67 MHz and 1297.67 MHz , close to the reported values of \varepsilon of 4 to 4.5 from the radar-based observations including the Magellan observations at 2.38 GHz ( 12.6 cm ) .