Radio Observation of Venus at Meter Wavelengths using the GMRT

TL;DR

This study presents the first interferometric imaging observations of Venus at meter wavelengths below 620 MHz using GMRT, revealing lower brightness temperatures than higher-frequency measurements and challenging existing thermal emission models.

Contribution

It provides new low-frequency radio observations of Venus, filling a gap in the spectral data and offering insights into Venusian thermal emission at these wavelengths.

Findings

Derived brightness temperatures at 606, 332.9, and 239.9 MHz are 526 K, 409 K, and <426 K.

Observed Tb values are consistent with previous low-frequency measurements but lower than high-frequency data.

Results challenge current thermal emission models for Venus at longer wavelengths.

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.