The Pathfinder of the Type-A satellites in the Chasing All Transients Constellation Hunters (CATCH) space mission is equipped with Micro-Pore Optics (MPOs) and four single-pixel Silicon Drift Detectors (SDDs). Due to the lack of position resolution in an individual SDD, we propose a new method based on the cross-arms in the point spread function (PSF) of MPOs to enhance the satellite's capability in identifying contaminating sources and locating target sources. By placing one detector on each of the horizontal and vertical cross-arms on the focal plane, we can use the changes in the relative counts on the cross-arms detectors to deduce the location of the source. Simulated observations demonstrate that, for a target source with a flux of 1 Crab and an exposure time of 200 s, the cross-arms detectors can identify contaminating source with the same flux level at an off-axis angle larger than 8', and improve positioning accuracy to 6'. Furthermore, we extend the simulation study to CATCH Type-A, which plans to use an SDD array. In situations where sources exhibit the same flux of 1 Crab and the exposure time is merely 1 s, a 16x16 SDD array is capable of identifying contaminating source with an off-axis angle greater than 2.4' and can achieve a positioning precision of 1.8'.
@article{arxiv.2603.04830,
title = {A New Method for Identifying Contaminating Sources and Locating Target Sources through the Cross-Arm Features of Micro Pore Optics},
author = {Yiming Huang and Lian Tao and Jin-Yuan Liao and Shuang-Nan Zhang and Stéphane Schanne and Bertrand Cordier and Shaolin Xiong and Juan Zhang and Zhengwei Li and Qian-Qing Yin and Xiangyang Wen and Sheng Yang and Min Gao and Donghua Zhao and Xiang Ma and Yue Huang and Liang Zhang and Liming Song},
journal= {arXiv preprint arXiv:2603.04830},
year = {2026}
}