GRAVITY：使用快速计量衰减系统减少GRAVITY $^+$中的噪声源
GRAVITY faint: reducing noise sources in GRAVITY$^+$ with a fast metrology attenuation system
摘要：
随着从GRAVITY升级到GRAVITY $^+$，该仪器将发展成为一个全天空的干涉仪，可以观测微弱的目标，如高红移活动星系核。观察最微弱的目标需要尽可能减少重力中的噪音源。主要的噪声源，尤其是在光谱的蓝色部分中，是测量激光到检测器上的反向散射。为了减少这种噪声，我们引入了两种新的计量模式。通过对硬件的微小改动和软件的调整，我们可以在观察期间调暗计量激光，而不会丢失相位参考。对于单光束目标，我们甚至可以关闭计量激光器，以获得探测器上的最大SNR。这些变化导致SNR改善超过整个频谱上平均的2倍，并且在当前由激光噪声主导的频谱部分中高达8倍。
英文摘要：
With the upgrade from GRAVITY to GRAVITY$^+$ the instrument will evolve into an all-sky interferometer that can observe faint targets, such as high redshift AGN. Observing the faintest targets requires reducing the noise sources in GRAVITY as much as possible. The dominant noise source, especially in the blue part of the spectrum, is the backscattering of the metrology laser light onto the detector. To reduce this noise we introduce two new metrology modes. With a combination of small hardware changes and software adaptations, we can dim the metrology laser during the observation without losing the phase referencing. For single beam targets, we can even turn off the metrology laser for the maximum SNR on the detector. These changes lead to an SNR improvement of over a factor of two averaged over the whole spectrum and up to a factor of eight in the part of the spectrum currently dominated by laser noise.
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