Beam-former for single beam, total power mode observations with Gauribidanur Radioheliograph

Abstract

The Gauribidanur RadioheliograPH (GRAPH) in its present configuration is operated in the interferometer mode over the frequency range 30-100 MHz. It is proposed to design a beam-former unit for use with the GRAPH so that the latter can also be operated in the single beam mode as a total power instrument. The latter mode of operation is expected to be advantageous for observations of transient emission from both the solar as well as non-solar radio sources in the sky, particularly in the above frequency range where presently large antenna arrays are not operational. Note the transient emission referred to is primarily non-thermal in nature. This implies that the intensity of the observed emission should increase with decrease in frequency. GRAPH observations are expected to be useful under such circumstances because of its low frequency coverage. The broad spectral window of the GRAPH, wide response pattern, and geographical location (77o E, 14o N) close to the equator which facilitates observations of both the northern and southern hemisphere almost equally are some of the advantages. As a precursor, it is proposed to implement the scheme for a small group of antennas.