Due to its extremely cold, dry, tenuous, and stable atmosphere, the Antarctica plateau is widely considered to be an excellent astronomical site. The long periods of uninterrupted darkness at polar sites such as Dome A provide a possibility of continuous observation for more than 3 months, which is quite suitable for time-domain astronomy. The second Antarctic Survey Telescope (AST3-2), the largest optical telescope in Antarctica so far, is a 0.5m entrance diameter large field of view optical imaging telescope which was deployed to Dome A, Antarctic in January 2015. It was used to study variable objects, such as supernova explosions and the afterglow of gamma-ray bursts, and to search for extrasolar planets. For the remoteness of the Antarctic plateau, it is designed to observe autonomously and operate remotely via satellite communication. With only 20 days attending maintenance annually, it has experienced 3 winters. It has observed for 3months in 2015 and 4 months in 2016. In the third year of 2017, the observing time of AST3-2 has covered all the polar night from March to September, the data reached to nearly 30TB with more than 200,000 exposures for searching supernovas and exoplanets. AST3-2 was also the only one telescope in the Antarctic plate that joined the optical observations of LIGO GW170817.
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.
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.
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 first Three Antarctic Survey Telescope (AST3-1), a 50/68cm Schmidt-like equatorial-mount telescope, is the first
automated Chinese telescope operating on the Antarctic plateau. It is planned to be in operations at Dome A, the highest
peak on the Antarctic plateau, in 2012. The telescope is unmanned during night-time operations in the Austral winter.
The telescope optics and mechanics, as well as the motors and position sensors, are exposed to a very harsh environment.
The mechanics is enclosed with a foldable tent-like dome to prevent snow, diamond dust and ice. While the drive boxes,
most circuit, power supply and computers are located inside the warm instrumental cabin. This article describes the
challenges the telescope control system encountered in night-time operations, such as the power supply limit, the harsh
meteorological condition, unattended testing, automatic operation, remote control and telemetry, etc. Some solutions are
also discussed in this paper, which are applied on the AST3-1 and waiting for validation. AST3-1 is also an exploration
of a larger telescope on the Antarctic.
The modern large telescope is endowed with advanced imaging systems and active optics, resulting in very high
peak angular resolution. The drive systems for the telescope must consequently be able to guarantee a tracking accuracy
better than the telescope angular resolution, in spite of unbalanced and sudden loads such as wind gusts and in spite of a
structure that, because of its size, can not be infinitely stiff, which puts forward a great challenge to the telescope' drive
system. Modern telescope's drive system is complicated, which performance and reliability directly affect the telescope
tracking performance and reliability. Redundant technology is one of the effective ways to improve the security of the
system. This paper will introduce one redundant synchronous control method for direct drive torque motor of large
diameter telescope drive system, which can effectively improve the telescope drive system tracking precision and
improve the reliability, stability and anti-jamming ability.
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.
Direct drive technology is the key to solute future 30-m and larger telescope motion system to guarantee a very high
tracking accuracy, in spite of unbalanced and sudden loads such as wind gusts and in spite of a structure that, because of
its size, can not be infinitely stiff. However, this requires the design and realization of unusually large torque motor that
the torque slew rate must be extremely steep too. A conventional torque motor design appears inadequate. This paper
explores one redundant unit permanent magnet synchronous motor and its simulation bed for 30-m class telescope.
Because its drive system is one high integrated electromechanical system, one complexly electromechanical design
method is adopted to improve the efficiency, reliability and quality of the system during the design and manufacture
circle. This paper discusses the design and control of the precise tracking simulation bed in detail.
Proc. SPIE. 8450, Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II
KEYWORDS: Telescopes, Control systems, Space telescopes, Astronomical telescopes, Servomechanisms, Large telescopes, Astronomical imaging, Optical instrument design, Electromagnetism, Control systems design
The direct drive motor of large aperture telescope, integrated with the telescope mechanic structure, has characteristics of
high load torque and large moment of inertia. The control method of drive system should be specially designed for the
heavy load. This article aims to list the key issues of engineering technology applied to large aperture telescope. Drive
control architecture and method, as well as design requirements of segmented direct drive motor on large astronomic
telescope, are discussed in this article.
A 30m giant telescope project, Chinese Future Giant Telescope (CFGT), has been proposed by Chinese astronomers. At
present, a series of key techniques are being developed. This paper explores a method to control direct drive servo motor
in giant telescope application, which is based on a segmented Surface-mounted Permanent Magnet Synchronous Motor
(SMPMSM). The losses of SMPMSM and the method of reducing the losses are discussed in this paper. Phase-controlled
rectification circuit is chosen to regulate rectified voltage according to the telescope status. Such design can
decrease the losses of the motor to some extent. In the control system Space-vector PWM (SVPWM) algorithm acts as a
control algorithm and three-phase voltage source inverter circuit acts as drive circuit. This project is subsidized by
Chinese National Natural Science Funds (10833004).