在HiCAT测试台使用泽尼克波前传感器校准MEMS促动器增益及其对宜居世界天文台运行的意义
Calibration of MEMS DM actuator gains using a Zernike wavefront sensor on the HiCAT testbed and implications for Habitable Worlds Observatory operations
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中文总结 AI 辅助
本文在HiCAT测试台用ZWFS校准MEMS DM促动器增益，提出线性与二次增益图计算方法，提升暗区挖掘效率与对比度，为HWO运行提供支撑。
中文摘要 AI 辅助
deformable mirrors（DMs，变形镜）是日冕仪仪器的关键组件，用于地面自适应光学，也将用于未来空间天文台如宜居世界天文台（HWO）和罗曼空间望远镜日冕仪（Roman CGI）。在这些空间任务中，变形镜作为波前传感与控制系统的一部分，用于“挖掘暗区”——消除残余恒星光，在焦平面创建高对比度区域以探测微弱伴星。为达到直接成像冷行星或反射光行星所需的深对比度（<1e-8），精确校准DM促动器增益至关重要，因为DM表面预期与实际的皮米级差异会显著降低暗区（DZ）挖掘效率，这会增加实现暗区所需的开销，并对天文台稳定性提出更严格要求。此外，DM增益随促动器行程变化，因此需要快速、原位重新计算增益图，以长期维持暗区挖掘效率。泽尼克波前传感器（ZWFS）非常适合该任务，因为它能高效提供皮米级灵敏度，且很可能已作为HWO低阶波前传感器的一部分搭载在航天器上。本文呈现了空间望远镜科学研究所（STScI）HiCAT测试台的结果：我们使用斐索干涉仪和ZWFS对波士顿微机械公司的952促动器微机电（MEMS）DMs进行了增益图校准，以对比两者性能。使用ZWFS时，我们围绕给定DM解采用局部线性拟合计算增益图，并提出推导更复杂二次解的形式体系，该形式体系计算量更大，但在每个促动器的大部分动态范围内精度更高。随后，我们利用这些技术校准HiCAT测试台的DMs，结果显示采用新增益图后暗区挖掘效率提高，且得益于这些校准，从14位控制电子设备升级到16位控制电子设备时对比度性能更佳。
英文摘要
Deformable mirrors (DMs) are a key component of coronagraph instruments performing adaptive optics on the ground, and for future space observatories such as HWO and Roman CGI. Here, they will be used as part of the wavefront sensing and control system to "dig a dark zone'' - remove residual stellar light to create a high-contrast region in the focal plane where faint companions can be detected. To reach the deep contrasts needed to directly image cool or reflected light planets (<1e-8) accurate calibration of the DM actuator gain is essential as picometer differences between the expected and realized DM surface can significantly degrade dark zone (DZ) digging efficiency. This increases the overheads needed to achieve a DZ and critically places more stringent requirements on observatory stability. Furthermore, DM gain varies with actuator stroke, necessitating rapid, in situ gain map recalculations to maintain DZ digging efficiency over time. Zernike wavefront sensors (ZWFS) are well-suited for this task as they efficiently provide picometer-level sensitivity and will likely already be included on board as part of a low order wavefront sensor for HWO. Here we present results from the HiCAT testbed at STScI where we calibrated gain maps for our Boston Micromachines 952-actuator micro electromechanical (MEMS) DMs using both a Fizeau interferometer and a ZWFS to compare performance. With the ZWFS we compute a gain map using both local linear fits around a given DM solution, and present a formalism for deriving more complex quadratic solutions which are more computationally intensive, but accurate over most of the dynamic range of each actuator. We then use these techniques to calibrate the DMs on the HiCAT testbed and show increased DZ digging efficiency with the new gain map and better contrast performance moving from 14 to 16 bit control electronics as enabled by these calibrations.
