Development of a High Performance Offset Gregorian Antenna for the Colorado State University (CSU)-CHILL National Radar Facility

在该MRI下，首席研究员将为科罗拉多州立大学(CSU)-CHILL雷达设施开发、获取、安装和测试一种新的高性能偏移格里高利天线。CSU- chill雷达设施已由CSU作为所有合格研究人员可用的多用户设施运行多年。该设施主要通过CSU和NSF之间的合作协议得到支持。新天线的规格要求严格，推动了天线设计和制造技术的发展。预计当前CSU-CHILL天线的副瓣电平将大幅降低。这种改进是由于偏移格里高利设计，消除了馈电喇叭和馈电支撑杆的堵塞。在任何平面上，交叉极化电平预计小于-35 dB。与现有天线相比，在所有平面上二维积分交叉极化能量与共极化能量的比率预计将降低约10 dB。这与预期（双向）旁瓣杂波到主瓣信号功率（16-20 dB）的显著降低相对应，并且相对于定焦抛物面反射器天线，双偏置设计显著提高了辐射极化纯度。在强降水回波空间梯度存在的情况下，特别是在强风暴条件下，要精确测量常规多普勒数据和完整的极化协方差矩阵，需要这些高性能的天线。目前，即使在存在适度的降水回波空间梯度的情况下，馈电支撑杆平面附近相对较差的副瓣性能也会导致许多关键的极化测量出现较大误差。新的天线性能有望使降水回波空间梯度增加近一倍，从而在极化测量中不产生显著误差。它还将大大提高常规多普勒数据的质量，特别是在数值模式同化数据的情况下。新天线将允许使用全协方差矩阵进行尖端研究，以极大地改善云和风暴微物理的定量遥感，并可能在未来使用数值模型同化极化数据。这将是世界上唯一一个使用s波段工作频率的研究气象雷达。在过去的几十年里，使用气象雷达的遥感一直是许多气象进步的推动力。这些进步包括对雷暴、山洪、龙卷风、飓风和微暴等恶劣天气现象的基本理解。这些知识中的大部分已经带来了实际的社会效益，例如已被业务气象机构采用的雷达预警系统。多年来，CSU-CHILL设施对这个知识库做出了重大贡献。新的天线系统将有助于保持强大的，正在进行的研究和教育活动在雷达气象研究的前沿。

Under this MRI, the Principal Investigator will develop, acquire, install and test a new high performance offset Gregorian antenna for the Colorado State University (CSU)-CHILL radar facility. The CSU-CHILL radar facility has been operated for many years by CSU as a multi-user facility available to all qualified researchers. The facility is supported primarily through a cooperative agreement between CSU and NSF. The specifications for the new antenna are stringent and push the antenna design and manufacturing technology. A substantial reduction in sidelobe levels over the current CSU-CHILL antenna is expected. This improvement results from the offset Gregorian design that eliminates blockages by the feedhorn and feed support struts. The cross-polarization levels are expected to be less than -35 dB in any plane. The ratio of two dimensional integrated cross-polarized energy to copolarized energy over all planes is expected to be reduced by around 10 dB compared with the current antenna. These correspond to significant reductions in expected (two-way) sidelobe clutter-to-mainlobe signal power (16-20 dB), and significant improvement in the radiated polarization purity offered by the dual-offset design relative to the prime-focus parabolic reflector antenna.These high antenna performance levels are needed to accurately measure conventional Doppler data and the full polarimetric covariance matrix in the presence of strong spatial gradients of precipitation echo, especially in severe storms. Currently, the relatively poorer sidelobe performance near the planes of the feed support struts tends to cause large errors in many of the key polarimetric measurements even in the presence of modest precipitation echo spatial gradients. The new antenna performance is expected to nearly double the precipitation echo spatial gradient that can be tolerated without significant error in the polarimetric measurements. It will also greatly improve the quality of conventional Doppler data especially in the context of data assimilation by numerical models. The new antenna will permit cutting-edge research using the full covariance matrix to greatly improve the quantitative remote sensing of cloud and storm microphysics, and possibly in the future use of assimilation of polarimetric data by numerical models. It will be the only such research weather radar of its kind in the world at S-band operating frequency.Remote sensing using weather radar has been the impetus for many meteorological advances over the last few decades. Such advances have included gaining fundamental understanding of severe weather phenomena such as thunderstorms, flash floods, tornadoes, hurricanes and microbursts. Much of this knowledge has led to practical societal benefits such as radar warning systems that have been adopted by the operational weather agencies. The CSU-CHILL facility has made substantial contributions to this knowledge base over the years. The new antenna system will help keep what are robust, ongoing research and educational activities at the cutting edge of radar meteorological research.