利用SCExAO上基于Lyot的低阶波前传感器解决低风效应问题
Addressing the low-wind effect with the Lyot-based low-order wavefront sensor on SCExAO
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中文总结 AI 辅助
本研究针对SCExAO现有LWE校正技术与日冕仪模式不兼容的问题，采用基于Lyot的LLOWFS，通过机器学习实现LWE差分活塞像差的在轨校正，提升SCExAO高对比度成像性能，助力小角距成熟系外行星探测。
中文摘要 AI 辅助
低风效应（Low-Wind Effect, LWE）是影响系外行星直接成像仪器日冕仪性能的已知问题，该效应在带有支腿的分段式及遮挡式光瞳中尤为显著，会因相位不连续性引发差分活塞误差，在低风条件下还会导致倾斜误差。LWE引发的低阶误差会造成日冕仪漏光，降低直接成像仪器的系外行星探测灵敏度。目前已开发出缓解LWE影响的被动与主动两种方案，被动方案如用低发射率材料涂覆支腿，主动方案采用波前传感器（Wavefront Sensor, WFS）。斯巴鲁望远镜的斯巴鲁日冕仪极端自适应光学（Subaru Coronagraphic Extreme Adaptive Optics, SCExAO）仪器也尝试通过测试多种专用WFS缓解LWE，这些技术在SCExAO上测试时已被证明可测量和校正LWE，但多数仍与SCExAO的日冕仪成像模式不兼容。为满足在日冕仪观测模式下校正LWE的高效解决方案需求，我们重新研究了SCExAO上的日冕仪WFS，即基于Lyot的低阶波前传感器（Lyot-based Low-order Wavefront Sensor, LLOWFS）。LLOWFS利用Lyot光阑反射的未使用星光，是经充分验证的技术，可通过探测焦平面掩模下游重成像焦平面或光瞳平面的低阶误差来防止日冕仪漏光。我们展示了机器学习辅助的LLOWFS在SCExAO红外臂中对Lyot日冕仪下游LWE引发的差分活塞像差进行的初始在轨测量与校正。LLOWFS在日冕仪模式下对LWE的初步校正效果令人鼓舞，将提升SCExAO未来的高对比度性能，实现小角距处成熟系外行星的探测。
英文摘要
The Low-Wind Effect (LWE) is a well-known issue that affects the coronagraphic capabilities of instruments optimized to take direct images of exoplanets. This effect is prominent in segmented and obstructed pupils with spider arms, causing differential pistons due to phase discontinuities and, in some cases, tip-tilt errors under low-wind conditions. LWE-induced low-order errors contribute to coronagraphic leakage and reduce the exoplanet detection sensitivity of direct imaging instruments. Solutions to mitigate the impact of LWE have been developed in both passive mode, such as coating the spider arms with low-emissivity material, and active mode using wavefront sensors (WFS). The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument at the Subaru Telescope also attempted to mitigate LWE by testing several dedicated WFS. Such techniques, when tested on SCExAO, have proven their ability to measure and correct LWE; however, most remain incompatible with SCExAO's coronagraphic imaging modes. Addressing the need for an efficient solution that can correct LWE in coronagraphic observing modes, we revisited the coronagraphic WFS on SCExAO, known as the Lyot-based Low-order Wavefront Sensor (LLOWFS). LLOWFS utilizes the unused starlight reflected off the Lyot stop and is a well-proven technique that can prevent coronagraphic leaks by sensing low-order errors in a re-imaged focal plane or pupil plane downstream of the focal plane mask. We present the machine-learned LLOWFS's initial on-sky measurement and control of the differential piston aberrations induced by the LWE downstream of a Lyot coronagraph in SCExAO's infrared arm. Preliminary LLOWFS corrections of LWE in the coronagraphic mode are encouraging and would leverage future high-contrast performance of SCExAO, enabling the detection of mature exoplanets at small angular separations.
发表机构
- National Astronomical Observatory of Japan, Subaru Telescope（日本国立天文台，昴星团望远镜）
- Astrobiology Center（天体生物学中心）
- Space Science and Engineering Initiative, College of Engineering, University of Hawai‘i（夏威夷大学工程学院空间科学与工程倡议）
- Institute for Astronomy, University of Hawaii（夏威夷大学天文学研究所）
- Optical Sharpeners（光学锐化器）
- University of Victoria（维多利亚大学）
- Korea Astronomy and Space Science Institute (KASI)（韩国天文学与空间科学研究所）
- Steward Observatory, University of Arizona（亚利桑那大学斯图尔德天文台）
- College of Optical Sciences, University of Arizona（亚利桑那大学光学科学学院）
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