Preface: Site testing campaign for the Large Optical/infrared Telescope of China

The Large Optical/infrared Telescope (LOT) is a ground-based 12 m diameter telescope which is proposed to be built in western China. The site selection for LOT in China began in 2016, and Ali was listed as one of the three candidate sites. Remote studies and local surveys have been carried out for more than 15 years in western China, and the results show that Ali is a promising site with comprehensive quality in terms of atmospheric and supporting conditions. An overview of the site testing campaign at the Ali site from 2016 to 2019 is presented. After the two years of data collection, the overall median seeing value is found to be 1.17 arcsec, the observable nights are 81.71% and the good observable nights are 71.76%. The weather conditions as follows, the median night temperature value is –5.18°C, the median night relative humidity value is 41.25%, the median night atmospheric pressure value is 540.92 hPa, the median night wind speed value is 7.41 m s–1 and the mainly wind direction is southwestern (SW). The median night sky background value is 22.07 magV. We also discuss the wind speed at different locations on-site, the possibility of light pollution and the effect of wind speed on differential image motion monitor (DIMM) seeing measurements.

“…The median sky background in V band is 22.07 magnitudes per square arcsecond. The detailed measurement results and analysis are available in other papers (Feng et al 2020;Cao et al 2020).…”

Section: Measurements and Resultsmentioning

confidence: 99%

Site testing campaign for the Large Optical Telescope at the Ali site

Liu

Yao

Yin

et al. 2020

“…With the rapid growth of astronomy in China in recent years, an ambitious project, the Large Optical/infrared Telescope (LOT), with the goal to construct a 12-meter telescope, was selected to be built in the next decade. In order to maximize the performance of the telescope, a site assessment campaign has been initiated for more than two years to identify the most suitable location to host it (Feng et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Site-testing at Muztagh-ata site I: ground meteorology and sky brightness

Esamdin

Hao

et al. 2020

Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions, one of the associated basic tasks. As one of three potential sites to host the 12-meter Large Optical/infrared Telescope (LOT), the Muztagh-ata site, which is located on the Pamir Plateau in Xinjiang, in west China, began its site-testing task in the spring of 2017. In this paper, we firstly start with an introduction to the site and then present a statistical analysis of the ground-level meteorological properties such as air temperature, barometric pressure, relative humidity, and wind speed and direction, recorded by an automatic weather station with standard meteorological sensors for a two-year duration. We also show the monitoring results of sky brightness during this period.

“…Located at an altitude of 4520 m on the Pamir Plateau in western China, the Muztagh-ata site has undergone an intense site-testing campaign for more than three years (Feng et al 2020), with the other two candidate sites being Ali (Liu et al 2020) and Daocheng (Song et al 2020). Already showing excellent optical observation conditions, such as ground meteorology (Xu et al 2020a), seeing conditions (Xu et al 2020b) and amount of clouds (Cao et al 2020a,b), the Muztagh-ata site is predicted to hopefully host China's future Large Optical/infrared Telescope (LOT) project.…”

Section: Introductionmentioning

confidence: 99%

Site-testing at Muztagh-ata site III: temperature inversion in surface-layer atmosphere

Esamdin

Feng

et al. 2020

In this article, we present detailed seasonal, monthly and daily statistics of temperature difference in the surface layer at the Muztagh-ata site based on the temperature measurements at two heights of 2m and 6m. We find that temperature inversion occurs frequently at our site during nighttime, especially during the cold season. Strong temperature inversion always represents stable atmospheric turbulence, which is crucial for an optical observatory. By analyzing the behavior of temperature inversion and its correlation with wind and cloud amount, one conclusion can be made that radiation inversion is the main reason for the existence of temperature inversion in the surface-layer at the Muztagh-ata site.