Development of High Sensitivity Rain and Snow Sensor in LHAASO-WFCTA

The Large High Altitude Air Shower Observatory (LHAASO) is located in Haizi Mountain, Daocheng County, Sichuan Province, with an average altitude of 4410 meters. It belongs to a typical alpine climate with rapid weather changes. The Wide Field of view Cherenkov Telescope Array (WFCTA), as one of the three major observation arrays of LHAASO, requires operation in the clear nights. To ensure the normal operation of the telescope, it is necessary to constantly detect rain and snow conditions, so that WFCTA can be closed promptly in case of rain and snow weather. However, due to the low temperature, traditional rain and snow sensors cannot work properly at the LHAASO site. Therefore, the heating device was induced to make the rain and snow sensors fit the weather in Daocheng. After designing and testing in the laboratory, the on-site experiment was also carried out at the LHAASO site. The results show that the high-sensitivity rain and snow sensor can maintain the temperature above ice point at the surface of the sensor in horrible weather, and can effectively monitor rain and snow in real-time at the LHAASO site, which can provide strong support for the normal operation of the Wide Field of view Cherenkov Telescope Array.