Operation of the Telescope Array Observatory

望远镜阵列（TA）天文台是北方半球最大的超高能宇宙射线（UHECR）探测器。目前正在对观测站（TAx4）进行升级，这将使部署的地面探测器（SD）数量增加一倍，增加的总仪器面积约为1800平方公里。 荧光检测器（FD）阵列俯瞰该SD阵列，提供关于检测到的事件的重要附加信息。该奖项支持犹他州大学的宇宙射线物理组运行TA天文台综合体一年。 该奖项支持团队，包括管理，工程和技术人员，他们全权负责设施维护，人员配备观察轮班和处理数据，并保持遵守土地管理局的土地使用法规。 天文台支持辅助和测试实验，包括最近主持闪电测绘阵列。通过ASPIRE项目协调的一个广泛的公共教育和外联方案每年收到数百万次在线访问，并指导成千上万的教师和学生开展活动。最近的TA数据分析已经确定了北方天空中高于57 EeV的UHECR的“热点”，其显著性为3.5 sigma。 天文台还发现，当比较热点区域内的事件与热点区域外的事件时，宇宙射线光谱形状存在差异，并且在最高能量下光谱具有明显的递减依赖性。然而，热点的来源仍然未知。TA和皮埃尔俄歇天文台（南半球最大的UHECR探测器）的测量之间的不一致性在最高能量下也很明显，包括对Xmax分布的宽度和形状的研究。 TAx4升级操作收集的额外数据，结合最近安装的FD的能量校准，将极大地提高仪器的灵敏度，以解决我们对宇宙中最高能量粒子的理解中这些重要的悬而未决的问题。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准。

The Telescope Array (TA) Observatory is the largest detector of ultra-high energy cosmic rays (UHECRs) in the northern hemisphere. An upgrade to the observatory (TAx4) is currently underway that will double the number of deployed surface detectors (SD) over an increased total instrumented area of approximately 1800 square-km. An array of florescence detectors (FDs) overlooks this SD array, providing important additional information on the detected events. This award supports the cosmic ray physics group at the University of Utah for one year of running the TA Observatory complex. The award supports the team, including managerial, engineering and technical staff, who have sole responsibility for facility maintenance, staffing observing shifts and handling data, and maintaining compliance with Bureau of Land Management land use regulations. The observatory supports auxiliary and test experiments, including recently hosting a lightning mapping array. An extensive public education and outreach program coordinated through the ASPIRE project receives millions of online visits each year, and directed activities reach tens of thousands of teachers and students. Recent TA data analyses have identified a “hotspot” of UHECRs above 57 EeV in the northern sky at 3.5 sigma significance. The observatory has also seen indications of differences in the cosmic ray spectral shape when comparing events within the hotspot region to those outside, as well as an apparent declination dependence of the spectrum at the highest energies. The source of the hotspot, however, remains unknown. Inconsistencies between the measurements of TA and the Pierre Auger Observatory, the largest UHECR detector in the southern hemisphere, are also apparent at the highest energies, including in the studies of the width and shape of the Xmax distributions. The additional data collected with the operation of the TAx4 upgrade, combined with the energy calibrations of the recently installed FDs, will greatly improve the sensitivity of the instrument toward resolving these important open questions in our understanding of the highest energy particles in the Universe.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.