FAST灵敏度优化及'回照'方式分析

摘要

针对500 m口径球面射电望远镜的灵敏度优化和天顶角超过26.4°时溢损增大引起系统噪声温度上升的问题.文中采用调整馈源照明进行灵敏度优化,提出"回照"方式降低系统噪声管温度的方法.当馈源为高斯照明时,边缘照明约为-12~-14 dB时点源观测的灵敏度达到极大值.在天顶角为30°、35°和40°时,分别选取最佳回照角为15°、21°和26°时,望远镜的灵敏度分别提高了19%、48%和100%.%An optimization of the sensitivity of FAST telescope is carried out by adjusting the edge taper of a feed with Gaussian illumination.An edge taper of-12~-14 dB gives the maximum sensitivity.While the zenith angle is beyond 26.4 degrees, a "back-illumination" technique is proposed to reduce the system noise temperature and optimize the sensitivity.The sensitivity is increased by 19%, 48% and 100% if a back-illumination angle of 15, 21 and 26 degrees is chosen for zenith angle of 30, 35 and 40 degrees, respectively.