摘要
FAST,the largest single-dish radio telescope in the world,has a 500-meter diameter main reflector and a 300-meter diameter illuminated area.It has a main reflector that can vary its shape,which continuously changes the shape of the illuminated area in reflector into a paraboloid.In this article,we propose a quasiCassegrain system for FAST.The detailed design results are provided.Such a quasi-Cassegrain system only needs to add a 14.6-meter diameter secondary reflector,which is close to the size of the feed cabin.The distance from the secondary reflector to the focus is only 5.08 m,and it has excellent image quality.In this quasi-Cassegrain system,the shape of the illuminated area in the main reflector continuously changes into an optimized hyperboloid.Using this quasi-Cassegrain system from frequency 0.5 GHz to 8 GHz,the multi-beam system can include 7 to 217 feeds.If this system is used in combination with Phased Array Feed(PAF)technology,more multi-beam feeds or a higher working frequency can be used.
FAST, the largest single-dish radio telescope in the world, has a 500-meter diameter main reflector and a 300-meter diameter illuminated area. It has a main reflector that can vary its shape, which continuously changes the shape of the illuminated area in reflector into a paraboloid. In this article, we propose a quasiCassegrain system for FAST. The detailed design results are provided. Such a quasi-Cassegrain system only needs to add a 14.6-meter diameter secondary reflector, which is close to the size of the feed cabin. The distance from the secondary reflector to the focus is only 5.08 m, and it has excellent image quality. In this quasi-Cassegrain system, the shape of the illuminated area in the main reflector continuously changes into an optimized hyperboloid. Using this quasi-Cassegrain system from frequency 0.5 GHz to 8 GHz, the multi-beam system can include 7 to 217 feeds. If this system is used in combination with Phased Array Feed(PAF) technology, more multi-beam feeds or a higher working frequency can be used.
作者
Ding-Qiang Su
Hua Bai
Xiang-Qun Cui
苏定强;白华;崔向群(School of Astronomy and Space Science&Key Laboratory of the Ministry of Education,Nanjing University,Nanjing 210023,China;National Astronomical Observatories/Nanjing Institute of Astronomical Optics and Technology(NIAOT),Chinese Academy of Science,Nanjing 210042,China)
