Abstract Details

Name: Ramesh Balasubramanyam
Affiliation: Raman Research Institute, Bangalore
Conference ID: ASI2020_385
Title : Building the RRI Efficient Linear-array Imager
Authors and Co-Authors : Ramesh Balasubramanyam
Abstract Type : Oral
Abstract Category : Instrumentation and Techniques
Abstract : Instantaneous sensitivity and field-of-view are two key parameters of a telescope. Traditionally, radio telescopes have had only a single pixel. This aspect is quickly changing with the move towards large sized focal plane array receivers. In this context, it is worth noting that the two can be traded to obtain a configuration that uses the receivers more efficiently. For a dish of size D fitted with N receivers, the A-Omega product is ~ D^2 N. This can be rewritten as 2 (D D/(N/2)) (N/2)^2. The first part, 2 (D D/(N/2)), implies two orthogonal apertures of elliptical cross section with an N/2 aspect ratio. The second part, (N/2)^2, indicates the number of simultaneous beams formed with N receivers. Thus, the resultant configuration is two 'fan-beam' telescopes of elliptical cross sections laid in a cross-configuration, each fitted with N/2 receivers. Then, by cross correlating each receiver from one set with each of the orthogonal set, one obtains the (N/2)^2 beams. This new optics entitled Efficient Linear-array Imager has been proposed recently (RB, 2014, MNRAS, 444, p2212). This approach has several benefits: (a) reduces the primary area; (b) the primaries become parabolic cylinders that are easy and economical to manufacture; (c) the increased instantaneous field-of-view makes the system suitable for studying transients; (d) the cross correlation based imaging system immunizes against receiver gain variations; (e) the telescope responds to very short-spacing sky signals. It has promises for the low-cost element needed for SKA, especially at high frequencies. To demonstrate these benefits a prototype cm-wavelength transit survey telescope is being built at the RRI field station at Gauribidanur, India. It will be equipped with two cm-wave (10-14 GHz) receivers to demonstrate the concept. In this talk, we will present the overall telescope system and its current status.