Preparatory Study for Constructing FAST, the World's Largest Single Dish
A 500-m aperture spherical telescope (FAST) was funded by the National Development and Reform Commission of China (NDRC) in July 2007 and will be located in the unique Karst region, a sinkhole-like landform, in Guizhou province. FAST can be seen as a modified ldquoArecibordquo type radio telescope using many innovative techniques, with as much as twice the collecting area and a wider sky coverage. FAST has, first, an active reflector, conforming to a paraboloid of revolution from a sphere in real time through actuated control, which enables the realization of wide bandwidth and full polarization capability by using standard feed design. Secondly, it has a light focus cabin suspension system, integrating optical, mechanical, and electronic technologies, reducing effectively the cost of the support structure and control system. With such a huge collecting area of more than 30 football fields, FAST will become the largest single dish ever built. Here we will summarize the FAST concept and the milestones achieved in experiments on its key technologies, i.e., site exploration, active reflector prototyping, focus cabin driving mechanism, measurement and control techniques, and the receiver layout. The Miyun FAST demonstrator also will be presented.