Seeing is an important index to evaluate the quality of an astronomical site.To estimate seeing at the Muztagh-Ata site with height and time quantitatively,the European Centre for Medium-Range Weather Forecasts reanal...Seeing is an important index to evaluate the quality of an astronomical site.To estimate seeing at the Muztagh-Ata site with height and time quantitatively,the European Centre for Medium-Range Weather Forecasts reanalysis database(ERA5)is used.Seeing calculated from ERA5 is compared consistently with the Differential Image Motion Monitor seeing at the height of 12 m.Results show that seeing decays exponentially with height at the Muztagh-Ata site.Seeing decays the fastest in fall in 2021 and most slowly with height in summer.The seeing condition is better in fall than in summer.The median value of seeing at 12 m is 0.89 arcsec,the maximum value is1.21 arcsec in August and the minimum is 0.66 arcsec in October.The median value of seeing at 12 m is 0.72arcsec in the nighttime and 1.08 arcsec in the daytime.Seeing is a combination of annual and about biannual variations with the same phase as temperature and wind speed indicating that seeing variation with time is influenced by temperature and wind speed.The Richardson number Ri is used to analyze the atmospheric stability and the variations of seeing are consistent with Ri between layers.These quantitative results can provide an important reference for a telescopic observation strategy.展开更多
This paper reports site survey results for the Infrared System for the Accurate Measurement of Solar Magnetic Field, especially in Saishiteng Mountain, Qinghai, China. Since 2017, we have installed a weather station,s...This paper reports site survey results for the Infrared System for the Accurate Measurement of Solar Magnetic Field, especially in Saishiteng Mountain, Qinghai, China. Since 2017, we have installed a weather station,spectrometers for precipitable water vapor, and Solar Differential Image Motion Monitor, and have carried out observations on weather elements, precipitable water vapor, and daytime seeing conditions for more than one year in almost all candidates. At Mt. Saishiteng, the median value of daytime precipitable water vapor is 5.25 mm and its median value in winter season is 2.1 mm. The median value of the Fried parameter of daytime seeing observation at Saishiteng Mountain is 3.42 cm. Its solar direct radiation data show that solar average observable time is 446 minutes per day and premium time is 401 minutes per day in 2019 August.展开更多
In order to evaluate the ground-based infrared telescope sensitivity affected by the noise from the atmosphere,instruments and detectors,we construct a sensitivity model that can calculate limiting magnitudes and sign...In order to evaluate the ground-based infrared telescope sensitivity affected by the noise from the atmosphere,instruments and detectors,we construct a sensitivity model that can calculate limiting magnitudes and signal-to-noise ratio(S/N).The model is tested with tentative measurements of M’-band sky brightness and atmospheric extinction obtained at the Ali and Daocheng sites.We find that the noise caused by an excellent scientific detector and instruments at-135℃can be ignored compared to the M’-band sky background noise.Thus,when S/N=3 and total exposure time is 1 second for 10 m telescopes,the magnitude limited by the atmosphere is 13.01^(m)at Ali and 12.96^(m)at Daocheng.Even under lessthan-ideal circumstances,i.e.,the readout noise of a deep cryogenic detector is less than 200 e-and the instruments are cooled to below-87.2℃,the above magnitudes decrease by 0.056^(m)at most.Therefore,according to observational requirements with a large telescope in a given infrared band,astronomers can use this sensitivity model as a tool for guiding site surveys,detector selection and instrumental thermal-control.展开更多
光学湍流的强弱和分布是描述天文台址优劣的重要参数.介绍了利用大气模式WRF(Weather Research and Forecasting Model)计算高美古站周围大气光学湍流参数的方法,这些参数包括C_n^2(大气光学湍流强度)廓线、大气相干长度、大气相干时间...光学湍流的强弱和分布是描述天文台址优劣的重要参数.介绍了利用大气模式WRF(Weather Research and Forecasting Model)计算高美古站周围大气光学湍流参数的方法,这些参数包括C_n^2(大气光学湍流强度)廓线、大气相干长度、大气相干时间、视宁度、等晕角和闪烁率等.包括模型计算方法的实现过程、模型的设置和模拟结果的验证.计算结果与云南高美古观测站DIMM(Differential Image Motion Monitor)的实测数据进行了对比.展开更多
Dome A in Antarctica has been demonstrated to be the best site on earth for optical,infrared,and terahertz astronomical observations by more and more evidence,such as excellent free-atmosphere seeing,extremely low per...Dome A in Antarctica has been demonstrated to be the best site on earth for optical,infrared,and terahertz astronomical observations by more and more evidence,such as excellent free-atmosphere seeing,extremely low perceptible water vapor,low sky background,and continuous dark time,etc.In this paper,we present a complete picture of the development of astronomy at Dome A from the very beginning,review recent progress in time-domain astronomy,demonstrate exciting results of the site testing,and address the challenges in instrumentation.Currently proposed projects are briefly discussed.展开更多
The daytime atmospheric turbulence profile is crucial for the design of both optical systems and the control algorithm of a solar Multi-Conjugate Adaptive Optics(MCAO) system. The Multi-Aperture Seeing Profiler(MASP) ...The daytime atmospheric turbulence profile is crucial for the design of both optical systems and the control algorithm of a solar Multi-Conjugate Adaptive Optics(MCAO) system. The Multi-Aperture Seeing Profiler(MASP) is a portable instrument which can measure the daytime turbulence profile up to^30 km. It consists of two portable small telescopes that can deliver performance similar to a SolarDifferential Image Motion Monitor +(S-DIMM+) on a 1.0 m solar telescope. In the original design of MASP, only two guide stars are used to retrieve the turbulence profile. In this paper, we studied the usage of multiple guide stars in MASP using numerical simulation, and found that there are three main advantages.Firstly, the precision of the turbulence profile can be increased, especially at a height of about 15 km, which is important for characterizing turbulence at the tropopause. Secondly, the equivalent diameter of MASP can be increased up to 30%, which will reduce the cost and weight of the instruments. Thirdly, the vertical resolution of the turbulence profile near the ground increases with the help of multiple guide stars.展开更多
The Large Optical/infrared Telescope(LOT)is a ground-based 12 m diameter optical/infrared telescope,which is proposed to be built in the western part of China in the next decade.To select the best site which satisfies...The Large Optical/infrared Telescope(LOT)is a ground-based 12 m diameter optical/infrared telescope,which is proposed to be built in the western part of China in the next decade.To select the best site which satisfies the construction and future operation of LOT,data monitoring and comparing are required for all the candidate sites.The comparison of most of the instruments was done at Xinglong Observatory.These instruments include weather station,all sky camera,sky background meter and differential image motion monitor(DIMM).This paper introduces the instruments used in LOT site monitoring and the instruments comparisons.The results show that the instrument is stable and the data uniformity of the identical instruments is good.This paper provides a fundamental description of LOT site monitoring.展开更多
基金funded by the National Natural Science Foundation of China(NSFC)the Chinese Academy of Sciences(CAS)(grant No.U2031209)the National Natural Science Foundation of China(NSFC,grant Nos.11872128,42174192,and 91952111)。
文摘Seeing is an important index to evaluate the quality of an astronomical site.To estimate seeing at the Muztagh-Ata site with height and time quantitatively,the European Centre for Medium-Range Weather Forecasts reanalysis database(ERA5)is used.Seeing calculated from ERA5 is compared consistently with the Differential Image Motion Monitor seeing at the height of 12 m.Results show that seeing decays exponentially with height at the Muztagh-Ata site.Seeing decays the fastest in fall in 2021 and most slowly with height in summer.The seeing condition is better in fall than in summer.The median value of seeing at 12 m is 0.89 arcsec,the maximum value is1.21 arcsec in August and the minimum is 0.66 arcsec in October.The median value of seeing at 12 m is 0.72arcsec in the nighttime and 1.08 arcsec in the daytime.Seeing is a combination of annual and about biannual variations with the same phase as temperature and wind speed indicating that seeing variation with time is influenced by temperature and wind speed.The Richardson number Ri is used to analyze the atmospheric stability and the variations of seeing are consistent with Ri between layers.These quantitative results can provide an important reference for a telescopic observation strategy.
基金sponsored by the National Natural Science Foundation of China (NSFC) under grant Nos 11427901 and 12273059the National Key R&D Program of China under grant No. 2021YFA1600500。
文摘This paper reports site survey results for the Infrared System for the Accurate Measurement of Solar Magnetic Field, especially in Saishiteng Mountain, Qinghai, China. Since 2017, we have installed a weather station,spectrometers for precipitable water vapor, and Solar Differential Image Motion Monitor, and have carried out observations on weather elements, precipitable water vapor, and daytime seeing conditions for more than one year in almost all candidates. At Mt. Saishiteng, the median value of daytime precipitable water vapor is 5.25 mm and its median value in winter season is 2.1 mm. The median value of the Fried parameter of daytime seeing observation at Saishiteng Mountain is 3.42 cm. Its solar direct radiation data show that solar average observable time is 446 minutes per day and premium time is 401 minutes per day in 2019 August.
基金funded by the National Natural Science Foundation of China(NSFC,Nos.11803089,U1931124)。
文摘In order to evaluate the ground-based infrared telescope sensitivity affected by the noise from the atmosphere,instruments and detectors,we construct a sensitivity model that can calculate limiting magnitudes and signal-to-noise ratio(S/N).The model is tested with tentative measurements of M’-band sky brightness and atmospheric extinction obtained at the Ali and Daocheng sites.We find that the noise caused by an excellent scientific detector and instruments at-135℃can be ignored compared to the M’-band sky background noise.Thus,when S/N=3 and total exposure time is 1 second for 10 m telescopes,the magnitude limited by the atmosphere is 13.01^(m)at Ali and 12.96^(m)at Daocheng.Even under lessthan-ideal circumstances,i.e.,the readout noise of a deep cryogenic detector is less than 200 e-and the instruments are cooled to below-87.2℃,the above magnitudes decrease by 0.056^(m)at most.Therefore,according to observational requirements with a large telescope in a given infrared band,astronomers can use this sensitivity model as a tool for guiding site surveys,detector selection and instrumental thermal-control.
文摘光学湍流的强弱和分布是描述天文台址优劣的重要参数.介绍了利用大气模式WRF(Weather Research and Forecasting Model)计算高美古站周围大气光学湍流参数的方法,这些参数包括C_n^2(大气光学湍流强度)廓线、大气相干长度、大气相干时间、视宁度、等晕角和闪烁率等.包括模型计算方法的实现过程、模型的设置和模拟结果的验证.计算结果与云南高美古观测站DIMM(Differential Image Motion Monitor)的实测数据进行了对比.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.11733007,11673037 and 11273019)the National Basic Research Program(973 Program)of China(Grant No.2013CB834900)the Chinese Polar Environment Comprehensive Investigation&Assessment Program(Grant No.CHINARE2016-02-03)。
文摘Dome A in Antarctica has been demonstrated to be the best site on earth for optical,infrared,and terahertz astronomical observations by more and more evidence,such as excellent free-atmosphere seeing,extremely low perceptible water vapor,low sky background,and continuous dark time,etc.In this paper,we present a complete picture of the development of astronomy at Dome A from the very beginning,review recent progress in time-domain astronomy,demonstrate exciting results of the site testing,and address the challenges in instrumentation.Currently proposed projects are briefly discussed.
基金supported by the National Natural Science Foundation of China (Nos. 11873068, 11433007, 11661161011 and 11673042)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA15010300)+1 种基金the International Partnership Program of Chinese Academy of Sciences (114A32KYSB20160018 and 114A32KYSB20160057)the special funding for Young Researchers at Nanjing Institute of Astronomical Optics & Technology and part of this work was carried out at CSUN, with support from NSF (Grant AST-1607921)
文摘The daytime atmospheric turbulence profile is crucial for the design of both optical systems and the control algorithm of a solar Multi-Conjugate Adaptive Optics(MCAO) system. The Multi-Aperture Seeing Profiler(MASP) is a portable instrument which can measure the daytime turbulence profile up to^30 km. It consists of two portable small telescopes that can deliver performance similar to a SolarDifferential Image Motion Monitor +(S-DIMM+) on a 1.0 m solar telescope. In the original design of MASP, only two guide stars are used to retrieve the turbulence profile. In this paper, we studied the usage of multiple guide stars in MASP using numerical simulation, and found that there are three main advantages.Firstly, the precision of the turbulence profile can be increased, especially at a height of about 15 km, which is important for characterizing turbulence at the tropopause. Secondly, the equivalent diameter of MASP can be increased up to 30%, which will reduce the cost and weight of the instruments. Thirdly, the vertical resolution of the turbulence profile near the ground increases with the help of multiple guide stars.
基金partly supported bythe Operation Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments,budgeted from the Ministry of Finance of China(MOF)and administrated by the Chinese Academy of Sciences(CAS)the grants from Joint Research Fund in Astronomy from the National Natural Science Foundation of China(Nos.U1831209 and U1731131)Youth Innovation Promotion Association CAS(No.2017077)。
文摘The Large Optical/infrared Telescope(LOT)is a ground-based 12 m diameter optical/infrared telescope,which is proposed to be built in the western part of China in the next decade.To select the best site which satisfies the construction and future operation of LOT,data monitoring and comparing are required for all the candidate sites.The comparison of most of the instruments was done at Xinglong Observatory.These instruments include weather station,all sky camera,sky background meter and differential image motion monitor(DIMM).This paper introduces the instruments used in LOT site monitoring and the instruments comparisons.The results show that the instrument is stable and the data uniformity of the identical instruments is good.This paper provides a fundamental description of LOT site monitoring.
