Kilometer-square Area Radio Synthesis Telescope KARST

In 1993, a large radio telescope (LT, now referred as the SKA) was proposed by astronomers from 10 countries at the 24 th 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 (a wide-band phased array), Australia (an array of spherical Luneburg lenses), Canada (large adaptive reflector of very long focal length), China (an Arecibo-style dish), the United States (the Allen telescope array), India (an array of steerable parabolic dishes) etc., for details, see http://www.skatelescope.org. In this document we will summarize the Chinese concept for the SKA and modeling experiments for this concept. Chinese astronomers are going to build a set of large (Arecibo-style) spherical reflectors by making use of the extensively existing karst landforms (Nan et al., 1996), which are bowlshaped 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 (Peng & Nan, 1997). The Chinese SKA, KARST, consists of about 30 individual elements, each roughly 200 m in diameter. As a forerunner for the KARST or SKA, a Five-hundred-meter Aperture Spherical Telescope (FAST) is proposed to start construction as a National Megascience Project of China, with an estimated cost of ~60 M US$ around the year 2004. The FAST will be over twice as large as the Arecibo radio telescope coupled with much wider sky coverage (Peng, Nan & Su, 2000). Technically, the FAST is not simply a copy of the existing Arecibo telescope but has rather a number of innovations. Firstly, the proposed main spherical reflector, by conforming to a paraboloid of revolution in real time through actuated active control, enables the realization of both wide bandwidth and full polarization capability while using standard feed design. Secondly, a feed support system, which integrates optical, mechanical and electronic technologies, will effectively reduce the cost of the support structure and control system. Pre-research on the FAST has become a key project in the Chinese Academy of Sciences, and great progress has been achieved. Some basic parameters of the FAST are demonstrated in Figure 1-1. It will have a main spherical reflector radius of R=300 m, a total projected diameter of up to 500 m, and an …