综合孔径射电望远镜冗余基线可见度噪声相关性对灵敏度的影响

Impact of the Correlation of Visibility Noise in Redundant Baselines on Radiometric Sensitivity of Aperture Synthesis Radio Telescope

综合孔径射电望远镜可见度噪声之间的相关性不但影响灵敏度的大小,而且影响阵列冗余对灵敏度的优化作用.本文研究对可见度噪声相关性起决定性作用的两个主要因素:目标场景亮温分布和接收机等效噪声温度,并利用仿真方法进行验证.通过灵敏度仿真实验,证明经过阵列冗余优化可以实现对灵敏度的优化,并且优化程度受到冗余基线可见度噪声之间相关性的影响.

In Earth remote sensing using aperture synthesis microwave radiometers,the brightness temperature distribution of observed scene is smooth,and the correlation between visibility noise is small.Therefore,the visibility noise is assumed to be uncorrelated when calculating the radiometric resolution.However,in the case of observing quiet Sun or solar bursts with the aperture synthesis radio telescope,it should not be assumed that the visibility noise is uncorrelated.The correlation between visibility noise of an aperture synthesis radio telescope plays a vital role in the computation of the radiometric resolution and modifying the improvement introduced by redundant baselines.Firstly,the study focuses on two factors:scene brightness temperature distribution and equivalent receiver noise temperature,both play a decisive role in the correlation.And simulations are used to verify the conclusion.Finally,additional radiometric sensitivity simulations are applied to demonstrate that the improvement of sensitivity can be achieved by optimizing the placement of redundant antenna elements.Moreover,the degree of improvement depends on the correlation level between the visibility noise of redundant samples.