大型分段空间任务系外行星高对比度成像中分段密度与内工作角（IWA）的权衡
Tradeoff between segment density and IWA for high-contrast imaging of exoplanets with a large segmented space mission
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中文总结 AI 辅助
该研究针对大型空间望远镜系外行星高对比度成像需求，提出联合优化主镜分段方案与焦平面掩模尺寸的方法，可显著放宽相位控制要求，对宜居世界天文台（HWO）有直接应用价值。
中文摘要 AI 辅助
在未来大型分段空间望远镜（如宜居世界天文台HWO）上使用日冕仪成像类地系外行星，需要在小于100毫角秒（mas）的分离度下达到10^-10的对比度，这要求分段相位控制精度达到几皮米。我们评估了如何通过优化望远镜和仪器设计来放宽这一约束，并量化分段相位像差对性能稳定性的影响。我们提出一种系统级方法，调整主镜分段方式和焦平面掩模尺寸（内工作角IWA）。我们比较了不同系统对分段相位误差的被动鲁棒性，以及泽尼克低阶波前传感器重建像差并恢复目标性能的能力。增大焦平面掩模半径或减少分段数量可同时提升被动鲁棒性和传感器重建能力：将掩模半径从3.5λ/D增大到6.5λ/D，可在IWA附近将相位约束放宽多达4倍；将分段数量从85个（5环）减少到7个（1环），可将相位约束放宽多达2倍；同样增大掩模半径，还会使传感器对分段活塞、倾斜和偏转模式的光子噪声灵敏度平均提升1倍。综上，联合优化分段方案和掩模尺寸，使低阶功率谱密度（PSD）包络被掩模阻挡，可显著放宽相位要求，补充主动校正，对HWO有直接意义。
英文摘要
Imaging Earth-like exoplanets with coronagraphs on future large segmented space telescopes such as the Habitable Worlds Observatory requires contrasts down to $10^{-10}$ at separations below 100 mas, imposing segment phasing control down to a few picometers. We evaluate how this constraint can be relaxed by optimizing telescope and instrument design, quantifying the impact on performance stability under segment phasing aberrations. We propose a system-level approach, adjusting the primary mirror segmentation and the focal-plane mask size (inner working angle). We compare the passive robustness to segment phasing errors across systems, and the ability of a Zernike low-order wavefront sensor to reconstruct aberrations and recover target performance. Increasing the focal-plane mask radius or decreasing segment count improves both passive robustness and sensor reconstruction: Increasing the mask radius from 3.5 to 6.5λ/D relaxes phasing constraints by up to a factor 4 near the IWA, and reducing the segment count from 85 (5 rings) to 7 (1 ring) relaxes them by up to a factor 2; The same mask radius increase also doubles, on average, the sensor's sensitivity to photon noise across segment piston, tip, and tilt modes. To conclude, jointly optimizing the segmentation scheme and mask size, so the low-order PSD envelope is blocked by the mask, can significantly relax phasing requirements, complementing active correction, with direct implications for HWO.
