Dome A is one of the best astronomical observatory sites on the earth. Unlike any other area, the telescopes have to be settled on the snow ground. In that case, it is very important to analysis the Snow mechanics in Dome A. However, due to the complexity and high variability of the snow, research in this field has progressed slowly. This article first compares five methods previously used for analyzing snow strength, and selects the most suitable method to estimate the snow strength in Dome A. Through this method, combined with the temperature and density data at different depths in the Dome A area, the paper estimates the strength of the surface snow is ranging from 0.6Mpa to 2.5Mpa (0-10m depth), and by the ultrasonic velocity measurements, the elastic modulus of the snow in Dome A has also been estimated at the range from 4Mpa to 600Mpa. Finally, the size of the wood foundation and the tilt angle of the snow surface under the wind speed of 10m/s were calculated by the static analysis. According to the tilt angle analysis, it was found that the elastic modulus of the original snow is too low to meet the requirements of tilt angle for the 2m class telescopes, and the snow foundation needs to have a densification treatment to make its density up to 530kg/m3. This study should also provide an useful reference for future infrastructure buildings, such as the construction of an airport or installation of some other large precision instruments at Dome A.
This study investigates the impact of wind screen structure on the observing environment of a telescope using the finite element method. A simplified geometric model comprising the telescope, fully open lightweight dome, and tower was established. The effects of wind screen structure under Antarctic wind loads were analyzed, followed by wind tunnel tests and data comparison. Results indicate that longitudinal rod arrangement is more effective than horizontal for wind reduction. Rod length and width do not significantly affect wind reduction, but turbulence kinetic energy correlates positively with rod length. Longitudinal rods with 50% transmittance satisfy wind speed and turbulence reduction requirements, although dome seeing reaches maximum. Higher transmittance increases wind pressure on the telescope surface. Ideal wind screen structure includes longitudinal rods, 25%50% transmittance, and shorter length with greater height.
The site testing shows that Antarctic Dome A is one of the best site on earth for astronomical observations, for wavelength ranging from visible to infrared and sub-millimeter. Continuous observation for nearly four months in polar nights makes Dome A quite suitable for time domain astronomy. In the past decade CCAA already led a series of Antarctic astronomy activities and telescope projects which will be introduced in this paper. The first generation telescope is Chinese Small Telescope Array known as CSTAR, which was composed of four identical telescopes with 145mm entrance pupil, 20 square degrees FOV and different filters, all pointing to the celestial South Point, mainly used for variable stars detection and site testing. The telescope was deployed in Dome A in Jan. 2008, and followed by automatic observations for four consecutive winters. Three Antarctic Survey Telescopes (AST3) is the second generation telescope capable of pointing and tracking in very low temperature, with 500mm entrance pupil, 8.5 square degree FOV. AST3-1 and AST3-2 were respectively mounted on Dome A in Jan. 2012 and 2015, fully remotely controlled for supernovae survey and exoplanets searching. In Aug. 2017, AST3-2 successfully detected the optical counterpart of LIGO Source GW 170817. Now AST3-3 is under development for both optical and near infrared sky survey by matching different cameras. Based on the experience of the above smaller sized optical telescopes, the 2.5m Kunlun Dark Universe Survey Telescope (KDUST) was proposed for high resolution imaging over wide field of view. Currently the KDUST proposal was submitted to the government and waiting for project review.
In this paper, we present the preliminary optical system design of AST3-NIR camera, a wide-field infrared imager for 50cm Antarctic surveying telescope (AST3-3) to be deployed to Dome A, the Antarctic plateau. It is a joint project in which China is responsible for telescope hardware and control, logistics and deployment. Australia is responsible for instrument hardware design and control, and power generation. The camera uses two mosaic Leonardo detectors with 1280 x 1032 pixels each. The instrument is designed with a field of view(FOV) of 28.10 X 46.10 at the pixel scale of 1.35” per 15µm pixel. It is optimized for K dark band (2.26μm to 2.49 μm). The main challenges of this design are to produce a well-defined internal pupil stop located within cryogenic condition which reduces the thermal background and the correction of off-axis aberrations due to the large available field. Since the operating temperature of the camera could vary from -35°C to -90°C, the refocusing mechanism needs to be designed within the camera. The optical performance of the system will be demonstrated. We show the opto-mechanical error budget and compensation strategy that allows the built design to meet the optical performance.
The Antarctic Survey Telescope-AST3 consists of three optical telescopes with 680mm primary mirror and 8 square degree field of view, mainly for observations of supernovas and extrasolar planets searching from Antarctic Dome A. The first two AST3 telescopes (AST3-1 and AST3-2) were successfully installed on Dome A by Chinese expedition team in Jan. 2012 and Jan. 2015 separately. Multi-anti-frost methods were designed for AST3-2 and the automatic observations are keeping on from March 2016. The best limited magnitude is 19.4m with exposure time 60s in G band. The third AST3 will have switchable interface for both optical camera and near infrared camera optimized for k dark band survey. Now the telescope is under development in NIAOT and the K-band camera is under development in AAO.
Antarctic is perfect site for astronomic observatory. But Antarctic also challenge the telescope design because of low temperature. The low temperature can impact characterization of telescope control system, especially for drive system. The following phenomenon can be produced due to low temperature. 1. The viscosity of grease will increase. 2. The clearance of bearing and gear will decrease. These two factors can lead to the increase in load torque of drive system with temperature drop. This would cause the bad tracking accuracy and low speed creeping. In order to overcome the impact of low temperature and improve the telescope’s track accuracy. In this paper, we describe some methods to overcome the effect of low temperature. First, the motor’s electromagnetism and lubrication in low temperature are analyzed. It shows that motor’s electromagnetism is little affected by temperature if the suitable material is selected. But the characterization of grease change dramatically with temperature. Second, the other lubricant material, solid lubricant, instead of lubricating grease is proposed. Contrasting experiment on two lubricant material proved that the solid lubricant is better than lubricating grease in low temperature environment. Third, besides the mechanical solution, a method from control point view is proposed to reduce the temperature influence. In this paper, the friction feedforward algorithm is used to compensate the torque change. Laboratory testing results will be presented verifying that friction feedforward can increase the tracking accuracy in low temperature environment.
The AST3 project consists of three large field of view survey telescopes with 680mm primary mirror, mainly for observations of supernovas and extrasolar planets searching from Antarctic Dome A where is very likely to be the best astronomical site on earth for astronomical observations from optical wavelength to thermal infrared and beyond, according to the four years site testing works by CCAA, UNSW and PRIC. The first AST3 was mounted on Dome A in Jan. 2012 and automatically run from March to May 2012. Based on the onsite winterization performance of the first AST3, some improvements such as the usage of high resolution encoders, defrosting method, better thermal control and easier onsite assembly et al were done for the second one. The winterization observation of AST3-2 in Mohe was carried on from Nov. 2013 to Apr. 2014, where is the most northern and coldest part of China with the lowest temperature around -50°. The technical modifications and testing observation results will be given in this paper. The third AST3 will be optimized from optical to thermal infrared aiming diffraction limited imaging with K band. Thus the whole AST3 project will be a good test bench for the development of future larger aperture optical/infrared Antarctic telescopes such as the proposed 2.5m Kunlun Dark Universe Survey Telescope project.
The preliminary site testing carried out since the beginning of 2008 shows the Antarctic Dome A is very likely to be the
best astronomical site on earth even better than Dome C and suitable for observations ranging from optical wavelength to
infrared and sub-millimeter. After the Chinese Small Telescope Array (CSTAR) which is composed of four small fixed
telescopes with diameter of 145mm and mounted on Dome A in 2008 for site testing and variable star monitor, three
Antarctic Survey Telescopes (AST3) were proposed for observations of supernovas and extrasolar planets searching.
AST3 is composed of 3 large field of view catadioptric telescopes with 500mm entrance diameter and G, R, I filter for
each. The telescopes can point and track autonomously along with a light and foldable dome to keep the snow and icing
build up. A precise auto-focusing mechanism is designed to make the telescope work at the right focus under large
temperature difference. The control and tracking components and assembly were successfully tested at from normal
temperature down to -80 Celsius degree. Testing observations of the first AST3 showed it can deliver good and uniform
images over the field of 8 square degrees. The first telescope was successfully mounted on Dome A in Jan. 2012 and the
automatic observations were started from Mar. 2012.
Dome A has been considered as one of the best observation sites on the earth. The First
AST3(three Antarctic Survey Telescopes) is on its way to Dome A by the 28th Chinese National
Antarctic research expedition. It will be the largest Optic telescope in Dome A after assembling and
testing in this austral summer. Firstly, this paper reports the method of collecting the vibration and
shock data from ShangHai to Dome A and analyses the data. Secondly, the package cushioning design
of the first AST3 is introduced in this paper according to the vibration and shock data. Finally, the
paper introduces the result of the dynamics analysis of the design and a test was done to verify the
performance of the package cushioning design. The dynamics analysis and the test indicate that the
package cushioning design can meet the demand of the Antarctic inland transportation.
Prelimenary site testing led by Chinese Center of Antarctic Astronomy (CCAA) shows that the highest point of the
Antarctic Plateau Dome A has very clear sky, good seeing, slow wind, low boundary layer and very low precipitable
water vapour which make it the best site on earth for optical/IR and sub-mm observations. Chinese Small Telescope
ARray (CSTAR) was installed at Dome A in 2008 and have automatically observed for about 3 antarctic winters. The
three Antarctic Schmidt telescopes(AST3) with entrance pupil diameter 500mm are the second antarctic project
proposed by CCAA and the first AST are being constructed in NIAOT now which is planned to be mounted on Dome A
at the beginning of 2011. All the tracking components were tested in the low temperature chamber and an adaptive
defrosting method is designed to prevent the frost building up on the schmidt plate.
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