基于CSST多色测光的时序测光精度分析

Analysis of the Precision of CSST Time-domain Photometric Observation

中国巡天空间望远镜(Chinese Survey Space Telescope,CSST)是中国的首个大型空间光学望远镜,将对包括系外行星探测在内的诸多科学目标开展研究,有望取得前沿科学进展.时序测光精度是CSST重要的性能指标,受到物理噪声和仪器噪声的影响,需要通过数值模拟对其分析和评估.模拟基于目前公布的CSST主要技术参数,建立了时序的恒星信号和噪声模型,以CSST的i波段为例,分析凝视观测模式下的测光精度.通过数值仿真,展示了孔径测光中各项噪声的贡献,特别是由指向抖动和像素响应不均匀性导致的抖动噪声.模拟结果还给出了测光孔径的推荐范围.为了获得更高的信噪比,可以减小仪器抖动振幅和像素不均匀性,或者采用参考星较差测光的方式.结果为CSST后续的时序测光精度与不同指标参数的相关性分析、系外行星探测能力评估以及测光数据处理提供了模拟数据的支撑.

The Chinese Survey Space Telescope(CSST)is the first large space optical telescope of China.It will perform scientific observations and yield important scientific results,e.g.multi-color photometry to find and characterize exoplanets.The precision of time-domain photometry affected by various astrophysical and instrument noises is crucial for exoplanet detection and characterization.This paper constructs a time-domain model to simulate the stellar signal and various noises based on the main technical parameters of CSST published so far.The precision of photometry is analyzed by modeling the signal and noises for an example of the gazing mode in the i band.We investigate and discuss the contribution of various noises while doing aperture photometry,especially the jitter noise caused by pointing jitter and pixel response inhomogeneity.The test results also provide the recommended size of aperture photometry.Jitter noise can be suppressed by reducing jitter amplitude and uniforming pixel or by using differential photometry with reference stars.Our simulation results can be applied to the precision prediction of time-domain photometry,the refinement of CSST instrumental specifications,evaluation of exoplanet detection capabilities,and data reduction progress for CSST.