LUVOIR-ECLIPS闭环自适应光学性能和对比度预测
LUVOIR-ECLIPS closed-loop adaptive optics performance and contrast predictions
摘要：
大型紫外/光学/红外探测器（LUVOIR）飞行任务概念的主要科学目标之一是通过直接成像探测和确定围绕附近恒星运行的类地系外行星的特征。它的日冕仪ECLIPS（生命行星系统的极端日冕仪）的成功取决于稳定来自大型分段反射镜的波前的能力，以便在几个小时的曝光时间内将光程差限制在数十皮米RMS。为了放宽对机械稳定性的限制，ECLIPS将配备波前传感和控制（WS&C）架构，以校正高达时间频率>~1 Hz的波前误差。这些误差可能主要是由航天器结构动力学激励振动的分段主镜。在这项工作中，我们提出了详细的模拟WS&C系统内的ECLIPS仪器和由此产生的对比度性能。本研究假设波前像差的基础上的有限元模型的模拟望远镜航天器结构动力学。然后根据自适应光学系统的模型计算波前残差，该模型包括数值传播以模拟真实的波前传感器和时间性能的分析模型。一个端到端的数值传播模型的ECLIPS，然后用来估计剩余的星光强度分布在科学探测器。我们发现，对比度的性能强烈依赖于目标恒星的星等和时空分布的波前误差从望远镜。在有显著振动的情况下，我们提倡使用激光计量来减轻高时间频率波前误差并增加任务产量。
英文摘要：
One of the primary science goals of the Large UV/Optical/Infrared Surveyor (LUVOIR) mission concept is to detect and characterize Earth-like exoplanets orbiting nearby stars with direct imaging. The success of its coronagraph instrument ECLIPS (Extreme Coronagraph for Living Planetary Systems) depends on the ability to stabilize the wavefront from a large segmented mirror such that optical path differences are limited to tens of picometers RMS during an exposure time of a few hours. In order to relax the constraints on the mechanical stability, ECLIPS will be equipped with a wavefront sensing and control (WS&C) architecture to correct wavefront errors up to temporal frequencies >~1 Hz. These errors may be dominated by spacecraft structural dynamics exciting vibrations at the segmented primary mirror. In this work, we present detailed simulations of the WS&C system within the ECLIPS instrument and the resulting contrast performance. This study assumes wavefront aberrations based on a finite element model of a simulated telescope with spacecraft structural dynamics. Wavefront residuals are then computed according to a model of the adaptive optics system that includes numerical propagation to simulate a realistic wavefront sensor and an analytical model of the temporal performance. An end-to-end numerical propagation model of ECLIPS is then used to estimate the residual starlight intensity distribution at the science detector. We show that the contrast performance depends strongly on the target star magnitude and the spatio-temporal distribution of wavefront errors from the telescope. In cases with significant vibration, we advocate for the use of laser metrology to mitigate high temporal frequency wavefront errors and increase the mission yield.
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