Abstract Details
| Name: SUMANJIT CHAKRABORTY Affiliation: IIT, Indore Conference ID: ASI2018_1735 Title : Effects of Ionosphere and Troposphere on Sensitive Radio Observations from 70 MHz to 24 GHz Authors and Co-Authors : Abhirup Datta. Center of Astronomy, Indian Institute of Technology Indore,Simrol Campus. Abstract Type : Poster Abstract Category : Sun and the Solar System Abstract : Any electromagnetic signal coming from outside the Earth’s atmosphere will get affected by the Ionosphere at centimeter and meter wavelengths while the same will get affected by the Troposphere between centimeter and millimeter wavelengths. In this work, we explore a uniform formalism to understand the highest radio frequencies where ionosphere poses a challenge for sensitive radio observations with upcoming telescopes like the SKA (Square Kilometer Array). We also investigate the lowest radio frequencies where Tropospheric effects are still significant for SKA-like observing capabilities. For a single radiometer, ionospheric effects are also pronounced through refraction, absorption and emission. All-sky averaged cosmological signals get corrupted due to these effects of ionosphere on low-frequency radio waves. It has been demonstrated the need for sensitive ionospheric calibration in order to proceed for deeper radio observations with single antenna. Electron density fluctuations in the ionosphere are affected by the nature of the solar disturbances. The solar activity follows variabilities at different temporal scales. The variability in the dynamical system of the ionosphere is a direct consequence of the forcing action by the solar radiation. It is well known that the various solar activities such as solar radio bursts and even sun-spot index display “1/ f †(flicker noise) characteristics as a function of time. Presence of such corruption term in the single antenna measurement makes it necessary to perform high time resolution calibration for the ionosphere. This makes a strong requirement on signal-to-noise in order to perform a fruitful ionospheric calibration. Similar issues exist with the effect of troposphere on radio signals received between centimeter and milli-meter wavelengths. Requirement of tropospheric calibration will influence the sensitive high frequency observations with radio interferometers like the SKA. In this study, we present a uniform study on the effects of both ionosphere and troposphere on radio observations from 70 MHz – 24 GHz. This study will present relative importance of each of the effects at each frequency bands across this huge range of frequencies. The context of this study is future SKA observations but it is not limited to only SKA and can interpreted for other similar telescopes as well. |