The Atacama Large Millimeter/submillimeter Array (ALMA) obtains spatial resolutions of 15 to 5 mas at 275–950 GHz (0.87–0.32 mm) with 16 km baselines. Calibration at higher frequencies is challenging as ALMA sensitivity and quasar density decrease. The band-to-band (B2B) technique observes a detectable quasar at a lower frequency that is closer to the target, compared to one at the target high frequency. Calibration involves a nearly constant instrumental phase offset between the frequencies and the conversion of the temporal phases to the target frequency. The instrumental offsets are solved with a differential gain calibration (DGC) sequence, consisting of alternating low- and high-frequency scans of strong quasars. Here we compare B2B and in-band phase referencing for high frequencies (>289 GHz) using 2–15 km baselines and calibrator separation angles between ∼0.°68 and ∼11.°65. The analysis shows the following: (1) DGC for B2B produces a coherence loss <7% for DGC phas...

中文翻译：

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2017年ALMA高频长基线活动：频段间和频段内相位校准技术与相位校准器分离角的比较

阿塔卡马大型毫米/亚毫米阵列（ALMA）在275–950 GHz（0.87–0.32 mm）的基线下，以16 km为基准，获得15到5 mas的空间分辨率。由于ALMA灵敏度和类星体密度降低，因此在较高频率下进行校准具有挑战性。带对带（B2B）技术与目标高频率处的频率相比，在更接近目标的较低频率处观察到可检测的类星体。校准涉及频率之间几乎恒定的仪器相位偏移以及时间相位到目标频率的转换。仪器失调通过差分增益校准（DGC）序列解决，该序列由强类星体的低频和高频扫描交替组成。在这里，我们比较了B2B和带内相位参考对于高频（> 289 GHz），使用2-15 km基线，校准器的分离角在〜0.°68和〜11.°65之间。分析显示以下内容：（1）B2B的DGC对于DGC相位产生了<7％的相干损耗。