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EPICS (experimental physics and industrial control system) is an open source, cross platform, distributed real-time control framework, which is widely used to control devices such as particle accelerators, large-scale experiments, large telescopes and other large-scale experiments. In the telescope control system, it is necessary to meet the real-time and distributed control requirements. For the distributed telescope observation and control system RACS2 (Remote Autonomous Control System), it can be divided into three layers: user interface layer, observation control layer and equipment control layer. This paper mainly discusses the content related to the device control layer, which is mainly used to control the equipment of a telescope. We use EPICS framework to realize the unified control of telescope, camera, dome, weather station and other equipment. The device control layer of RACS2 realizes the conversion from EPICS protocol to RACS2 protocol through EPICSBridge module, so users can control the devices through RACS2.

In the field of radio astronomy, the 21cm absorption line of HI is an important way to explore the large-scale structure and evolution history of the universe. The working frequency of FAST's 19 beam receiver is 1.05GHz to 1.45GHz, and the main observation object is to conduct an accurate and rapid intensity mapping survey of extragalactic HI’s signal. Aiming at the 21cm spectral line of the object, we designed a parallel data processing platform to mitigate the influence of foreground, instrument, radio frequency, standing wave and other noises on the spectral data, then generate the image data of the whole sky region. At present, we divide the process into flux calibration, bandpass and baseline correction, radio frequency interference marking and data gridding work, etc. The whole project was programmed in Python, and Cython was used for some projects to speed things up.

RACS2 (Remote Autonomous Control System V2) is a special distributed control system for telescope control. In order to complete the heavy and complex observation task in astronomical observation, RACS2 fully considered the modular design and extensible design at the beginning of design, which has the characteristics of decentralization and automatic component discovery. The bottom layer of RACS2 is written in modern C + + language, which provides rich scalability. In addition, RACS2 also provides full-featured Python interface binding, which is convenient for modular management of device components. Aiming at the actual process of telescope automatic observation, RACS2 has designed three modules: task management module, task execution module and log management module. These three modules correspond to the three components of RACS2, including Scheduler, Executor and Logger, which covering the creation, management, execution and recording of observation tasks, so that RACS2 can meet the complex astronomical observation requirements.

The Antarctica Plateau with high altitude, low water vapor and low thermal emission from the atmosphere is known as one of the best sites on the earth for conducting astronomical observations from the near infrared to the sub-millimeter. Many optical astronomical telescopes are proposed by Chinese astronomical society at present, such as Kunlun Dark Universe Survey Telescope (KDUST), 6.5-meter optical telescopes and 12-meter optical and infrared telescopes. Accurate estimation of the sky background brightness of proposed sites provides the scientific basis for instruments design and observatory site selection. Based on this requirement, a near-infrared sky brightness monitor (NISBM) based on InGaAs photoelectric diode is designed by using the method of chopper modulation and digital lock-in amplifier in the near infrared band of J, H, Ks. The adaptability of the monitor under extremely low temperature conditions in Antarctica is promoted by taking advantage of PID heating and fault detection system. Considering the weak signal of Ks band in Antarctica, a surface blackbody is equipped for real-time calibration. For the adverse circumstances to human, an EPICS and Web based Remote Control Software is implemented for unattended operation. The NISBM has been successfully installed in Dome A, Antarctica on January 2019.

CSTAR2 is a new telescope array which consists of two telescopes with 145mm-aperture and an equatorial mount, which was planned to update the CSTAR (Chinese Small Telescope Array) installed at Dome A, Antarctica in 2008. Since the previous camera was out of product, a brand new CCD camera with 1K*1K pixels was developed for CSTAR2, which was tested function well at -80℃ to prove the ability to work at Antarctica in a long period. The camera has a well performance and the readout noise is as low as 3.99e-rms. An equatorial mount made by NIAOT (Nanjing Institute of Astronomical Optics & Technology) can rotate the telescope to point almost entire sky area. In order to control CSTAR2 in an efficient way, a multi-level software control system was developed which contains three main layers: device control layer, coordinating operation layer, user interface layer. The whole system was planned to achieve automatic observation and remote operation under the conditions of poor satellite-link network.

The 1.2m Quantum Teleportation Telescope imaging system is a multi-band imaging system with dual channels called ‘red end’ and ‘blue end’. Each channel includes a CCD camera and a filter wheel system, and the blue end contains a focusing system. In order to improve the tracking accuracy, the guiding CCD is designed and deployed. The imaging system studies the mass of the black hole and the structure of AGN by observing the variation of AGN spectral line. In order to improve the observation efficiency, we design and implement a multi-level remote unattended observation and control system. The system adopts the framework of combining RTS2 and EPICS. EPICS is used to realize the individual control of each device. We defined status code and split device properties for debugging purpose or high-level invocating purpose. The EPICS Channel Access is integrated into the RTS2 software and a set of configurations in XML format is designed so that the RTS2 module can find the EPICS application. In the RTS2 layer, we developed a module for the coordinated control of the equipment. The module is responsible for sending instructions to the telescope and the guiding module according to the pre-defined list of observation plans, switching to the corresponding filter, and performing exposure operations. Finally, we developed web service and used web pages as user interface, which makes it convenient for users to control the telescope remotely and complete the observation task.

The Astronomical Imaging System of a 1.2-meter-aperture Telescope is a multi-band imaging system with red and blue channels. The mass and structure of AGN central black hole are studied by observing the change of AGN spectral line. We designed an optical system with dual channels, changing the focal length ratio of telescope from f/8.429 to f/5 through the lens, and divide the optical path into red and blue channels through the beam splitter. The red waveband is 650nm1000nm and the blue waveband is 400nm-650nm. Each channel has a CCD camera. We set up focusing lens before the camera of blue channel to compensate the difference focusing length between red and blue channel after the red channel being focused by adjusting the telescope. For the realization of three groups of broadband photometry and twenty-four groups of narrowband photometry, an automatic filter wheel system is designed to switch the filter. At the same time, in order to reduce the influence of temperature drift of the filter, a constant temperature adjusting system for filter wheel box is carried out. In order to overcome the issue that the telescope itself does not have enough tracking accuracy, a guiding system for the imaging system is designed and implemented. Finally, we designed and implemented a multi-level software control system so that the users can remotely control the telescope.

A 1K*1K CCD camera is designed, implemented and tested for CSTAR telescope in Antarctica, including its mechanics, CCD controller, power and temperature controller unit. Mechanical and electronic design for low temperature environment is taken into consideration fully. The camera has reliable mechanics and stable electronics performance. The readout noise is as low as 3.99 when the CCD readout speed is 100kpixs/s. We fully tested every part of the camera in a Cryogenic refrigerator (-86 degree centigrade) and proved that our camera has the ability to work in Antarctica for a long term. Finally, the camera was tested on the CSTAR telescopes to take observations and the imaging quality meets requirement.

A guiding system is designed, implemented and tested for our 1.2-meter Quantum-Teleportation Telescope Imaging System, due to the lack of accuracy of its own star tracking function. This paper at first introduces some key technologies of the system including star extraction, offset computation, star tracking, offset conversion and exception handling. The guiding system is implemented as a RTS2 device, and interacts with a guiding CCD and telescope. The workflow control of the guiding process is pushed forward by a finite-state machine. The system is tested in Delingha, Qinghai province. In cloudless condition, the guiding system can work for 15 min continuously, and long-exposure images produced by main CCDs can meet scientific requirements.

Automatic focusing (AF) technology plays an important role in modern astronomical telescopes. Based on the focusing requirement of BSST (Bright Star Survey Telescope) in Antarctic, an AF system is set up. In this design, functions in OpenCV is used to find stars, the algorithm of area, HFD or FWHM are used to degree the focus metric by choosing. Curve fitting method is used to find focus position as the method of camera moving. All these design are suitable for unattended small telescope.

The development of astronomical techniques and telescopes currently entered a new vigorous period. The telescopes have trends of the giant, complex, diversity of equipment and wide span of control despite of optical, radio space telescopes. That means, for telescope observatory, the control system must have these specifications: flexibility, scalability, distributive, cross-platform and real-time, especially the fault locating and fault processing is more important when fault or exception arise. Through the analysis of the structure of large telescopes, fault diagnosis expert system of large telescope based on the fault tree and distributed log service is given.

In the present work, a modified vertical Bridgman technique for GaAs crystal is developed. The VB configuration in prototype includes a quartz ampoule and a quartz crucible. The quartz ampoule was sealed in order to prevent volatilization of components. Because the decomposition pressure of GaAs ia about 1 atm. at its melting point, the quartz ampoule can keep its shape under 1300 degrees Celsius in air atmosphere during GaAs growth. Seeded 25 mm diameter crystals are grown at the rate of about 0.1 - 0.6 mm/hr under the temperature gradient about 10 degrees Celsius/cm at the solid-liquid interface, and electrical properties of as-grown GaAs crystal are discussed.

Cr:LiCaAlF6 crystal was grown by modified Bridgman method. The growing process was described in detail. The distribution of Cr along the crystal growth direction was measured and the results showed that the segregation coefficient of Cr is less than 1 under this condition.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Precision machining can achieve high levels of accuracy through the use of a highly accurate spindle, straight feed mechanisms, a rigid base and a single-point diamond tool. Research is underway aimed at achieving even higher levels of accuracy by adding computers, non-contact sensors and piezoelectric actuators for in-process measurement and control to the workpiece. Based upon such idea, a workpiece form accuracy in-process measurement and control system is proposed in this paper. The principle and a few key techniques for the system are discussed and some preliminary experiments are given in the paper.