Using the monthly data sets during 1951-2008 from standard upper-air stations, the spatial and seasonal distributions of upper turbulence over China are studied, and the atmospheric turbulence intensity at the pressure levels of 200hPa, 100hPa and 50hPa are given in this paper, providing scientific reference for relevant experiments. The intensity of atmospheric turbulence is closely related to height; at 200hPa pressure level, a downward trend of turbulence intensity from north to south is shown over China; at 100hPa, the turbulence is decreasing from south to north, weak turbulence occurs in the area north to 40°N; at 50hPa in near space, the turbulence in the west is slightly weaker than that in middle and east of the country. Influenced by seasonal variations of the mean circulations at each altitude, strong turbulence always occurs in winter while weak one in summer; but at 100hPa, the distribution of turbulence is evenly all over the country in summer, while weak turbulence occurs above the Tibetan Plateau and north of 40°N in winter; at 50hPa, the turbulence is weak in autumn, and a bit strong in summer. On the whole, the results could reflect the characteristic distributions of atmospheric optical turbulence in most general circumstances, and the most important value is to give the relative regional distributions of turbulence, to evaluate regional optical conditions on a macro scale.
The earth atmosphere is an unavoidable part of the satellite-ground laser communication link, which has a serious impact on the laser signal transmission. Poor weather conditions will cause the equipment at ground sites to be disabled, heavy cloud cover will interrupt the communication line, as well as the attenuation caused by atmospheric absorption and scattering will introduce an average reduction in signal power. Moreover, the irradiance scintillations introduced by atmospheric turbulence will cause the jitter of the received power and the deterioration of the bit error rate of laser communication. The speckle effect of laser caused by phase distortion will cause the decrease of tracking accuracy and the fiber coupling efficiency of PAT (pointing, capturing, tracking) unit. The sky background brightness, direct sunlight, etc., can cause the overall performance of the acquisition, tracking, and communication system to decline. The atmospheric polarization disturbance will decrease the mixing efficiency of coherent laser communication system, and the deflection effect of atmosphere will affect the alignment accuracy of PAT unit, and so on. All of these can seriously affect the transmission and communication of laser signals, and become the technical bottleneck restricting the development and application of high-speed satellite-ground laser communication. In this study, based on several typical optical stations in different geographical areas including the Ali site in Tibet, the Delingha site in Qinghai and so on, the research on the availability of atmospheric channel for laser communication is carried out. The characteristics of atmospheric channel of ground stations are analyzed, including the cloud cover, atmospheric transmittance, irradiance, atmospheric turbulence and so on, and the availabilities of single station and multi-station are discussed, aims to establish an evaluation system for the study of atmospheric channel availability of ground sites, as well as to put forward the availability criteria for atmospheric channel, and the results will provide scientific basic data for the performance of the ground optical receiving network for laser communication.
Publisher’s Note: This paper, originally published on 22 December 2020, was replaced with a corrected/revised version on 12 March 2021. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.
AliCPT-1 is the first CMB degree scale polarimeter to be deployed to the Tibetan plateau at 5,250m asl. AliCPT-1 is a 95/150GHz 72cm aperture, two lens refracting telescope cooled down to 4K. Alumina lenses image the CMB on a 636mm wide focal plane. The modularized focal plane consists of dichroic polarization-sensitive Transition-Edge Sensors (TESes). Each module includes 1,704 optically active TESes fabricated on a 6in Silicon wafer. Each TES array is read out with a microwave multiplexing with a multiplexing factor up to 2,000. Such large factor has allowed to consider 10's of thousands of detectors in a practical way, enabling to design a receiver that can operate up to 19 TES arrays for a total of 32,300 TESes. AliCPT-1 leverages the technological advancements of AdvACT and BICEP-3. The cryostat receiver is currently under integration and testing. Here we present the AliCPT-1 receiver, underlying how the optimized design meets the experimental requirements.
Research on the Antarctic site has shown that it has outstanding features such as excellent seeing, low water vapor, and extremely long polar nights. It is exceptional condition for astronomical observation. Many people think that Dome A is promising as the best site in Antarctica. However, there is only one summer station at Dome A, it has been difficult to conduct continuous site monitoring. The numerical weather prediction method - Weather Research and Forecasting (WRF) model is a good tool to solve the above difficulties. The WRF model was configured with 3 nested domains and 60 vertical levels. The numerical approach, by using of meteorological parameters and parameterization of optical turbulence, can provide the near-surface weather conditions, cloudiness, the precipitable water vapor (PWV) and optical turbulence parameters. We present the preliminary results with WRF model at Dome A in January 2012. The mean temperature for the entire month is -31.57°C, the mean pressure is 584.73 HPa, the median PWV is 0.25 mm, the relative humidity is between 40% and 80% most of the time and the mean wind speed is 4.78m/s. Although the integral seeing value is 0.84 arc second, the free atmospheric seeing is only about 0.26 arc seconds.
HinOTORI is a China-Japan co-construction 50cm telescope with three-color (u', RC, and IC) simultaneous imager. The main purpose aims at identifying gravitational-wave electromagnetic counterpart and performing follow-up observation from ultraviolet to near-infrared band. The telescope locates at the Tibet plateau, China, with 5100 meters high altitude. The construction of the telescope has already finished, and now it is going on commissioning. In this paper we focus on the system and devices for remote control of multi-devices, including telescope, mount, dome, three cameras, Power Distribution Units (PDUs), sky monitor, and so on. We will also present system performance and site condition based on observations collected during commissioning.
HinOTORI is a 50cm telescope which is co-constructed and shared by China and Japan. It can image in u’, Rc and Ic bands simultaneously, its main scientific observation targets are gravitational waves (GWs) optical counterparts (OTs). The installation of the telescope has been finished, and the engineering first light observation was carried out in May 2018. This paper will give an overall introduction and parameters of the telescope and then concentrate on a focusing method, which aims at obtaining the best focus position from the fitting equation. The reason of the best position shifting is also discussed.
KEYWORDS: Sensors, Observatories, Calibration, Black bodies, Near infrared, Indium gallium arsenide, Temperature metrology, Signal to noise ratio, Infrared radiation, Electronics
The Ngari (Ali) observatory is located in Ngari, Tibet, a region known as “the roof of the roof of the world.” The observatory benefits from abundant photometric nights, low perceptible water vapor, high transmittance, and good seeing. Due to these advantages, it promises to be one of the best locations in the world at which to make infrared and submillimeter observations. However, no data on the sky background radiation at this location are available, impacting the planning of future facilities at the observatory. To remedy this deficiency, a near-infrared sky brightness monitor (NISBM) has been designed to obtain data in the J, H, and Ks bands. This monitor is based on an InGaAs photoelectric diode and uses chopper modulation and digital lock-in amplifier processing, which considerably enhance its signal-to-noise ratio, detectivity, and data acquisition speed. An independent device has been designed for each band (J, H, and Ks) and calibrated in the laboratory. The NISBM was installed at the Ngari observatory in July 2017 and has obtained the first NIR sky brightness data for that location.
Tibet is known as the third pole of the earth. The Ngari (Ali) observatory in Tibet is a good site, and promising to be one of the best place for infrared and submillimeter observations in the world. However, there is no data available for sky background brightness in such place. In the near infrared band of J, H, Ks, a NIR sky brightness monitor (NISBM) is designed based on InGaAs photoelectric diode. By using the method of chopper modulation and digital lock-in amplifier processing, the SNR (Signal Noise Ratio), detectivity and the data acquisition speed of the device is greatly improved. The NISBM has been installed in Ngari observatory in July of 2017 and obtained the first data of NIR sky brightness at Ngari observatory.
In this invited paper, we implement a new way to study the stellar oscillations, pulsations and their evolutionary properties with long uninterrupted and continuous precision observations over 150 days from the ground, and without the regular interruptions imposed by the earth rotation. PAIX–First Robotic Antarctica Polar Mission– gives a new insight to cope with unresolved stellar enigma and stellar oscillation challenges and offers a great opportunity to benefit from an access to the best astronomical site on Earth –DomeC–. The project is made of low cost commercial components, and achieves astrophysical measurement time-series of stellar physics fields, challenging photometry from space that shows large gaps in terms of flexibility during the observing runs, the choice of targets, the repair of failures and the inexorable high costs. PAIX has yet more advantages than space missions in observing in UBV RI bands and then collecting unprecedented simultaneous multicolor light curves of several targets. We give a brief history of the Astronomy in Antarctica and describe the first polar robotized mission PAIX and the outcome of stellar physics from the heart of Antarctica during several polar nights. We briefly discuss our first results and perspectives on the pulsating stars and its evolution from Antarctica, especially the connection between temporal hydrodynamic phenomena and cyclic modulations. Finally, we highlight the impact of PAIX on the stellar physics study and the remaining challenges to successfully accomplish the Universe explorations under extreme conditions.
The site survey in western China has been carried out since 2003. Remote studies and local surveys are performed,
and Oma site, Ali area in southwest Tibet, has been selected in 2005 to make site testing measurements. The
monitoring results show that Ali area can be the best choice for astronomical observations over the East Asian
regions. A new site in Ali has been identified and begun construction in 2010 for small telescopes and detailed
site characterization. This paper reviews the long term site survey, presents site characteristics in Tibet, and
introduces current status of the new Ali observatory.
The atmospheric turbulence characteristics are important to evaluate the quality of ground-based astronomical
observatory. In order to characterize Ali observatory, Tibet. we have developed a single star Scidar (SSS) system,
which is able to continuously monitor the vertical profiles of both optical turbulence and wind speed. The main
SSS configuration includes a 40cm telescope and a CCD camera for fast sampling the star scintillation pattern.
The SSS technique analyzes the scintillation patterns in real time, by computing the spatial auto-correlation and
at least two cross-correlation images, and retrieves both C2n (h) and V (h) vertical profiles from the ground up to
30km. This paper presents the first turbulence measurements with SSS at Ali observatory in October, 2011. We
have successfully obtained the profiles of optical turbulence and wind speed, as well as the key parameters for
adaptive optics, such as seeing, coherence time, and isoplanatic angle. The favourable results indicate that Ali
observatory can be an excellent astronomical observatory.
The high plateaus in west China (Tibet) may provide good candidate sites possibly for ELT projects. According to satellite weather data, we found that a certain area in Tibet shows potentiality for good astronomical observations with less cloud coverage. We have explored through west Tibet to watch its topography in summer, 2004. We reanalyze meteorological data collected by GAME-Tibet project. We have started weather monitor in two candidate sites in west China; Oma in western area of Tibet and Karasu near the western boundary of China. Monitoring observations using modern astronomical site-testing techniques such as a DIMM and an IR cloud monitor camera will be started to catch up continuous monitoring of seeing and cloud coverage.
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