CHARA阵列延迟线：升级、性能与未来方向
CHARA Array Delay Lines: Upgrades, Performance and Future Directions
AI总结：
CHARA阵列通过升级延迟线系统，实现了高精度干涉观测，并展望了未来基线扩展和先进观测模式的发展。
摘要：
长基线光学和近红外干涉仪阵列能够实现高角分辨率，并使详细的天体物理测量成为可能。干涉仪使天文学家能够观测处于不同演化的恒星，以及双星、恒星盘和活动星系核的研究。CHARA阵列是位于美国威尔逊山天文台的长基线干涉仪阵列。在CHARA的操作核心是延迟线，它们通过地球自转时使所有望远镜的光学路径长度相等，并补偿由大气湍流引起的光学路径变化。我们报告了CHARA阵列光学延迟线的最新升级和性能，以实现高精度干涉测量。遗留系统已经运行了超过二十年，且难以获得替换部件。从2021年中期开始，控制系统经历了一次重大升级，将过时的VME架构替换为现代的混合FPGA和Linux系统；这种现代化工作持续到2024年底。我们描述了硬件/软件的变化、伺服架构以及实验室和天文观测性能。升级后的系统实现了残余延迟线车跟踪误差约为12纳米，与遗留系统相同水平，以及100-130Hz的控制带宽，允许在R、H和K波段进行干涉跟踪。初步调试揭示了关键问题，如计量时间戳抖动和振动引起的可见性损失，这些问题已被诊断并解决。我们注意到持续和未来的工作旨在将基线扩展到1公里，并支持双场干涉和消隐等先进观测模式。本文是当前和未来CHARA阵列使用以及下一代仪器设计的参考。
英文摘要：
Long baseline optical and infrared interferometric arrays achieve high angular resolution and enable detailed astrophysical measurements. Interferometers have enabled observations of stars at various stages of evolution, as well as studies of binary stars, circumstellar disks, and active galactic nuclei. The CHARA Array is a long-baseline interferometric array at the Mount Wilson Observatory, USA. At the core of CHARA operations are the delay lines, which equalize the optical path length for all telescopes as the Earth rotates and compensate for optical path variations induced by atmospheric turbulence. We report recent upgrades and performance of the CHARA Array optical delay lines for high-precision interferometric observations. The legacy system had been operational for over two decades, and it was increasingly difficult to acquire replacement parts. Beginning in mid-2021, the control system underwent a major upgrade, replacing the aging VME-based architecture with a modern hybrid FPGA and Linux-based system; this modernization continued through the end of 2024. We describe hardware/software changes, the servo architecture, and lab/on-sky performance. The upgraded system achieves residual delay line cart tracking errors of $\sim12$~nm, the same level as the legacy system, and a control bandwidth of 100-130~Hz, allowing fringe tracking across the R, H, and K bands. Initial commissioning revealed key issues such as metrology time-tick jitter and vibration-induced visibility loss, which were diagnosed and resolved. We note ongoing and future efforts to extend baselines up to 1~km and support advanced observing modes such as dual-field interferometry and nulling. This paper is a reference for current and future use of the CHARA Array and for next-generation instrument design.
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