Executive Summary : | The Cosmic Microwave Background (CMB) radiation is the faint light that permeates the Universe. It is the remnant afterglow from the very early Universe. The field of CMB studies has been awarded two nobel prizes in Physics , in 1978 and 2006. The cosmology community is in agreement that there are two more guaranteed Nobel prizes waiting to be awarded to CMB studies, namely for the discovery of the so-called 'B-mode' polarization of the CMB and of 'spectral distortions of the CMB'. This proposal will target the latter problem, while building a firm footing for the Indian cosmology community to step into experimental research of the former. We seek funding to develop, build, and deploy the first element of APsERa - Array of Precision Radiometers for the Epoch of Recombination - operating over 2-4 GHz to detect the faint additive distortion in the CMB spectrum from the formation of the first atoms. Operating in a radio-quiet location in India, the first element of APsERa will enable key science results including a precise measurement of the mid-frequency radio sky-spectrum, a blind survey of fast radio bursts, and detecting galactic radio recombination lines over 2-4 GHz. APsERa marks the leap, combining current expertise in theory and low-frequency radio astronomy, to take a step in building mid-frequency followed by high-frequency arrays with cryogenically cooled receivers. There is no other dedicated experiment in India, or the world for that matter, proposed to detect the distortions in the CMB spectrum from cosmological recombination. APsERa will be a world-leader in the soon to bloom field of CMB spectral distortion experiments. |