Abstract

Implications of Radio Telescope Antenna through 3D Radiation Pattern

Author(s): Debojyoti Halder*

Radio telescopes are based on the basic principle of optical telescopes called the “optical seeing”, where the astronomical object is viewed through a combination of lenses. Unlike optical telescopes, radio telescopes use antennae as the viewing instrument. The wavelength is in radio spectrum and moreover an image is also not formed for seeing. Thus, the radio telescopes may be said to use the principle of “indirect seeing”, which means, after the signals from the radio source in the sky are received using the antenna, they are processed involving electronics and co mputers thereby developing an image using pseudo color which can be seen with the human eye. The prime instrument of a radio telescope is the antenna. Based on the performance of the antenna, the quality of the image is justified. The purpose of this paper is to focus some critical concepts of antenna theories from the engineering point of view, essential for successful operation of the radio telescopes. A basic unit of radiation may be developed to describe the dependence of all the variables involved in r adiation. This unit is called brightness in astronomy. If the brightness is known, then it may be used to calculate the received spectral power etc. on the Earth. In this paper, the relationship between the brightness of the sky and the received power is c ritically examined, particularly when using a radio telescope antenna. The attenuation for the electromagnetic waves passing through an absorbing medium is also considered briefly and the limitations are discussed discussed.