Abstract
The Chasing All Transients Constellation Hunters (CATCH) space mission is an intelligent constellation consisting of 126 micro-satellites in three types (A, B, and C), designed for X-ray observation with the objective of studying the dynamic universe. Currently, we are actively developing the first Pathfinder (CATCH-1) for the CATCH mission, specifically for type-A satellites. CATCH-1 is equipped with Micro Pore Optics (MPO) and a 4-pixel Silicon Drift Detector (SDD) array. To assess its scientific performance, including the effective area of the optical system, on-orbit background, and telescope sensitivity, we employ the Monte Carlo software Geant4 for simulation in this study. The MPO optics exhibit an effective area of 41 cm\(^2\) at the focal spot for 1 keV X-rays, while the entire telescope system achieves an effective area of 29 cm\(^2\) at 1 keV when taking into account the SDD detector’s detection efficiency. The primary contribution to the background is found to be from the Cosmic X-ray Background. Assuming a 625 km orbit with an inclination of \(29^\circ \), the total background for CATCH-1 is estimated to be \(8.13\times 10^{-2}\) counts s\(^{-1}\) in the energy range of 0.5–4 keV. Based on the background within the central detector and assuming a Crab-like source spectrum, the estimated ideal sensitivity could achieve \(1.9\times 10^{-12}\) erg cm\(^{-2}\) s\(^{-1}\) for an exposure of 10\(^4\) s in the energy band of 0.5–4 keV. Furthermore, after simulating the background caused by low-energy charged particles near the geomagnetic equator, we have determined that there is no need to install a magnetic deflector.
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Acknowledgements
We would like to express our gratitude to all colleagues in the CATCH team for their contributions throughout this work. We are also grateful for the support provided by Tencent. Furthermore, we would like to extend our thanks to Stéphane Schanne and Bertrand Cordier for their insightful suggestions regarding the arrangement of our detectors. This work is supported by the National Natural Science Foundation of China (NSFC) under the Grant Nos. 12122306, 12003037 and 12173056, the Strategic Priority Research Program of the Chinese Academy of Sciences XDA15016400, the CAS Pioneer Hundred Talent Program Y8291130K2. We also acknowledge the Scientific and technological innovation project of IHEP E15456U2.
Funding
We acknowledge funding support from the National Natural Science Foundation of China (NSFC) under the Grant Nos. 12122306 and 12003037, the Strategic Priority Research Program of the Chinese Academy of Sciences XDA15016400, the CAS Pioneer Hundred Talent Program Y8291130K2, and the Scientific and technological innovation project of IHEP E15456U2.
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Yiming Huang and Juan Zhang wrote the main manuscript. Lian Tao and Jingyu Xiao assisted with the critical revision of the article. All authors reviewed the manuscript and contributed to the development of the simulation studies for CATCH-1.
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Huang, Y., Zhang, J., Tao, L. et al. Simulation studies for the first pathfinder of the CATCH space mission. Exp Astron 57, 3 (2024). https://doi.org/10.1007/s10686-024-09924-0
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DOI: https://doi.org/10.1007/s10686-024-09924-0