Demonstrator Review for KARST

In 1993, a large radio telescope (LT, now referred as the SKA) was proposed by astronomers from 10 countries at the 24 General Assembly of URSI. The SKA would be a telescope array with a total effective collecting area of about one square kilometer. There are various concepts, worldwide, for realizing the SKA project. Extensive efforts have been made, e.g, by project teams in The Netherlands, Australia, Canada, China, the United States, India etc., for details, see http://www.skatelescope.org. Chinese astronomers are going to build a set of large spherical reflectors by making use of the extensively existing karst landforms in south China [1], which are bowl-shaped limestone sinkholes named after Karst, a Yugoslavian geologist. Now we refer to such efforts for the SKA as the Kilometer-square Area Radio Synthesis Telescope project, i.e., KARST [2]. The Chinese SKA, KARST, consists of about 30 individual elements, each roughly 200 m in diameter. The total cost of the KARST would be estimated of ~ 850 M US$. As an engineering demonstrator for the KARST, a Five-hundred-meter Aperture Spherical Telescope, the FAST, is proposed, with an estimated cost of ~60 M US$. The FAST will be over twice as large as the Arecibo radio telescope coupled with much wider sky coverage [3]. Technically, the FAST is not simply a copy of the existing Arecibo telescope but has rather a number of innovations. Firstly, the proposed active main spherical reflector [4], by deforming the illuminated area to a paraboloid of revolution in real time, enables the realization of both wide bandwidth and full polarization capability while using conventional feed design. Secondly, a cable support system for feed, which integrates optical, mechanical and electronic technologies, will effectively reduce the cost of the support structure [5]. In this document we will summarize modeling experiments for the Chinese concept.