标题： 具有1微米路径长度灵敏度的多基线12 GHz大气相位干涉仪 显示英文标题

标题： A Multi-Baseline 12 GHz Atmospheric Phase Interferometer with One Micron Path Length Sensitivity

摘要： 我们为位于夏威夷茂纳凯阿山山顶附近的亚毫米波阵列（SMA）建造了一个五站式12 GHz大气相位干涉仪（API）。每个站在未占用的SMA天线垫的底部运行，使用一个商业低噪声混频模块，该模块连接到一个0.7米的离轴卫星天线，接收来自地球同步卫星的宽带、白噪声样的信号。这些信号通过模拟相关器处理，以产生所有基线投影范围从33到261米的站对之间的相位延迟。每条基线的振幅和相位以每秒8千赫兹的速率连续测量，处理后，以每秒10赫兹的频率输出。进一步的信号处理和数据缩减由Linux计算机完成，包括移除目标卫星的昼夜运动。站点放置在地平面以下，并结合使用低温系数埋设光纤电缆的环境屏蔽，提供了优异的系统稳定性。灵敏度以均方根路径长度表示为1.3微米，相当于SMA最高工作频率时约1度的相位偏差。两个主要的数据产品是：（1）在各种时间尺度上观测到的相位的标准偏差，以及（2）相位结构函数。这些由API实时统计的数据，提供了一种对同时进行的SMA天文观测所经历的相位前表面畸变的估计。API数据与本地透明度测量和天气预报一起，在帮助规划望远镜上的科学观测调度方面也起着重要作用。 显示英文摘要

摘要： We have constructed a five station 12 GHz atmospheric phase interferometer (API) for the Submillimeter Array (SMA) located near the summit of Mauna Kea, Hawaii. Operating at the base of unoccupied SMA antenna pads, each station employs a commercial low noise mixing block coupled to a 0.7 m off-axis satellite dish which receives a broadband, white noise-like signal from a geostationary satellite. The signals are processed by an analog correlator to produce the phase delays between all pairs of stations with projected baselines ranging from 33 to 261 m. Each baseline's amplitude and phase is measured continuously at a rate of 8 kHz, processed, averaged and output at 10 Hz. Further signal processing and data reduction is accomplished with a Linux computer, including the removal of the diurnal motion of the target satellite. The placement of the stations below ground level with an environmental shield combined with the use of low temperature coefficient, buried fiber optic cables provides excellent system stability. The sensitivity in terms of rms path length is 1.3 microns which corresponds to phase deviations of about 1 degree of phase at the highest operating frequency of the SMA. The two primary data products are: (1) standard deviations of observed phase over various time scales, and (2) phase structure functions. These real-time statistical data measured by the API in the direction of the satellite provide an estimate of the phase front distortion experienced by the concurrent SMA astronomical observations. The API data also play an important role, along with the local opacity measurements and weather predictions, in helping to plan the scheduling of science observations on the telescope.