Initial site monitoring plan for the 14.5 meters optical/infrared telescope

The Chinese Academy of Sciences (CAS) has already launched an ambitious project to build a large optical/ infrared telescope leading by National Astronomical Observatories, CAS and joined by several other institutes of the CAS. The telescope will be located at the platform A of Lenghu site in Qinghai province, with an altitude of 4,350 meters. The effective aperture of the telescope is 14.5 meters with a segmented primary mirror composed of 120 hexagonal segments. The telescope is planned to be equipped with a suite of high performance scientific instruments as its first generation instruments. These includes an optical imaging spectrographs, a near infrared imager that will be assisted with sodium laser guide star adaptive optics system, and a near infrared high-resolution spectrographs. The performance of the telescope and the instruments will be limited by the local astronomical weather conditions. Parameters like wind speed/directions, relative humidity, temperature will have direct impact on the structures, materials, components of the telescope, its enclosure, and the scientific instruments. Cloudiness, atmospheric transparency, extinction, seeing, sky background, etc. will also affect the observation performances of the telescope and the instruments, which could also be used as a guide for operation of the telescope and instruments as well as be used in scientific data reductions. Especially considering that the telescope will have laser guide star adaptive optics system, the site monitoring plan should also include the monitoring of vertical turbulence profile, isoplanatic angle, coherent time, and if possible the monitoring of sodium layer altitude and density, which are all important for the performance of the laser guide star adaptive optics system. To ensure that the telescope and its instruments can achieve their optimal performances, it is essential to have a comprehensive site monitoring plan in place. This plan will involve the continuous monitoring of various atmospheric and environmental parameters at the telescope site. The data collected will be crucial for understanding the local astronomical conditions and for making informed decisions regarding to the operation and maintenance of the telescope and its instruments. In this paper, the initial site monitoring plan for the 14.5 meters optical / infrared telescope will be presented. The plan covers the parameters to be monitored, the reasons for monitoring them, and the instruments planned to be used.