论文标题
为了更好地理解OPD的限制，以提高VLTI的敏感性和对比度
Towards a Better Understanding of OPD Limitations for Higher Sensitivity and Contrast at the VLTI
论文作者
论文摘要
非常大的望远镜干涉仪（VLTI）中光路差（OPD）的精确控制对于在我们银河系中心的黑洞表征至关重要 - 导致2020年诺贝尔物理学奖。现在，要进一步推动这些OPD限制，在8M单元望远镜（UT）上实现100nm OPD RMS，以允许VLTI的更高对比度和灵敏度。这项工作计算了VLTI的理论大气OPD极限为5nm和15nm RMS，当前使用明亮的大气条件下的明亮靶标时，UT分别为200nm和100nm RMS和100nm的RMS和100nm的辅助望远镜（AT'S）。我们找到了$ f^{ - 17/3} $电源法的实验证据理论上从望远镜过滤的效果中预测了ATS的效果，而ATS目前尚未观察到UT的ATS。我们可以将一系列以抑制谐波振荡器为模型的振动镜，我们能够将重力边缘跟踪器的UT OPD PSD建模到$ <1nm/\ sqrt {hz} $ rmse to to 100Hz，最多可以充分解释一个隐藏的$ f^{ - 17/3} $ power on the uts on uts on uts on uts。发现60-90Hz范围内和40-50Hz的振动频率通常主导着重力的闭环OPD残差。与重力数据相关的加速度计，发现40-50Hz范围内的强大贡献来自M1-M3镜，而60-100Hz贡献的大部分功率可能来自M4-M10之间。从振动镜模型中可以看出，要在特定基准（具有OPD $ \ sim $ \ sim $ 200NM RMS）中实现Sub 100nm OPD RMS，几乎所有振动源都需要删除100Hz以下的所有振动源。
Precise control of the optical path differences (OPD) in the Very Large Telescope Interferometer (VLTI) was critical for the characterization of the black hole at the center of our Galaxy - leading to the 2020 Nobel prize in physics. There is now significant effort to push these OPD limits even further, in-particular achieving 100nm OPD RMS on the 8m unit telescopes (UT's) to allow higher contrast and sensitivity at the VLTI. This work calculated the theoretical atmospheric OPD limit of the VLTI as 5nm and 15nm RMS, with current levels around 200nm and 100nm RMS for the UT and 1.8m auxillary telescopes (AT's) respectively, when using bright targets in good atmospheric conditions. We find experimental evidence for the $f^{-17/3}$ power law theoretically predicted from the effect of telescope filtering in the case of the ATs which is not currently observed for the UT's. Fitting a series of vibrating mirrors modelled as dampened harmonic oscillators, we were able to model the UT OPD PSD of the gravity fringe tracker to $<1nm/\sqrt{Hz}$ RMSE up to 100Hz, which could adequately explain a hidden $f^{-17/3}$ power law on the UTs. Vibration frequencies in the range of 60-90Hz and also 40-50Hz were found to generally dominate the closed loop OPD residuals of Gravity. Cross correlating accelerometer with Gravity data, it was found that strong contributions in the 40-50Hz range are coming from the M1-M3 mirrors, while a significant portion of power from the 60-100Hz contributions are likely coming from between the M4-M10. From the vibrating mirror model it was shown that achieving sub 100nm OPD RMS for particular baselines (that have OPD$\sim$200nm RMS) required removing nearly all vibration sources below 100Hz.
