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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.

Effective and continuous monitoring of space debris in satellite orbit is an important issue in resolving potential threats to aerospace equipment. The SDM (Space Debris Monitoring)-16803 is a front-illuminated high-readout-speed, low-noise scientific CCD camera designed for the needs of space debris monitoring telescopes. The camera is designed with drift scanning function in which mode the moving target will be presented as a static image, so that a fixed telescope can track the moving space target. The electronics of the camera provides driving signals for the CCD, samples the video signals of the CCD, and also communicates with the host computer. The maximum readout speed of the CCD is 10Mpixels. The mechanics structure of the camera is designed with a sealed chamber in which a TEC (Thermo Electric Cooler) is used for cooling the sensor and provide a stable temperature.

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.

With the increase of human activities in space, a large number of space artifacts have been generated around the Earth which called Near Earth Objects (NEO), most of which are space debris. CMOS image sensor can achieve very high frame rate by electronical shutter and suitable for NEO observation with its fast moving. For space objects observation, key technologies of a large-format and high-rate scientific CMOS camera were studied, including low-noise readout and low-interference refrigeration technology, real-time processing algorithm, high-speed data transmission technology, system integration technology and high precision timing technology , etc. A 4K*4K pixel scientific CMOS camera is introduced in this paper with 24fps rate in full frame mode and high timing accuracy of exposure synchronization with 10ns, which has great advantages for the initial orbit positioning of the space objects. The overall size of the camera is 143mm * 160mm * 168mm. The readout noise of the camera is about 4.4e-. At present, the camera has been installed and running at Xinglong Observatory.

The Wide Field Survey Telescope (WFST) is a proposed 2.5m-aperture wide field survey telescope intended for dedicated wide field sciences in China. The focal-plane instrument is a mosaic CCD camera comprising 9 pieces of 9K×9K pixels CCD chips. In order to verify the WFST mosaic solution, we designed a 2×2 mosaic camera test system using CCD303- 88. The mechanical design of vacuum chamber, cryogenic refrigeration of CCD, mosaic CCD technique and multi CCD control electronic have been implemented on this system. We design a CCD controller capable of controlling two pieces of CCDs and a power supply module for the controller. The cryogenic refrigeration control is implemented with a refrigerator and temperature control electronics.

Scientific Complementary Metal-Oxide Semiconductor (sCMOS) image sensor has higher readout speed, higher resolution, lower readout noise than traditional Charged Coupled Device (CCDs). Since the orbital debris observation has the demand for high speed imaging system, we designed and built a sCMOS camera, and developed the corresponding operational software system. The operational software contains three lays: a software development kit (SDK), Common Language Runtime(CLR) library and an operational software with a Graphic User Interface (GUI) named PXViewer. Each of them were tested and benchmarked. Several data acquisition modes including photo, timer, continuously capture and video are implemented for different observation scenarios. Users can get fully control and operation of the sCMOS camera through the software system, including cooling, data acquisition and configuration. During the benchmark, the sCMOS camera is able to capture image of 4128*4096 pixels at 7.8 frame per second (fps), and 2064*2048 pixels at 30 fps.

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 infrared astronomy is a very important branch of astronomy. Imaging observation is the basic approach to conduct infrared astronomy observation. Therefore, infrared Focus Plane Array (FPA) detector is needed for an infrared telescope. Detection toward celestial body need the detector to have high performance like extremely low dark current and low readout noise. Therefore, we designed a test equipment based on a 640 × 512 InGaAs array detector with a cryocooler which can cool the detector down to 77K. The detector is InGaAs of SITP-Hu-I type which is sensitive to 0.9us ~ 1.7um band. The test equipment is composed of a vacuum cryocooling system, a mechanical system and an electronical system. The vacuum cryocooling system can provide a low-temperature vacuum environment for the detector, and the mechanical system provides firm supporting. The electronic system provides the driver and readout of the detector.

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.

Infrared sky background level is an important parameter of grounded infrared astronomy observations, which should be firstly measured in a good infrared observatory site, and only the site with low background level is suitable for infrared observations. Infrared sky background level can provide background data for the design of related infrared instruments. However, there is no such data available for major sites in China. Based on the requirement, In order to supplement the current site survey data and guide the design of future infrared instruments, a multiband near-infrared sky brightness monitor (MNISBM) based on an InSb sensor is designed in this paper. The MNISBM consists of optical system, mechanical structure and control system, detector and cooler, high gain readout electronic system, operational software. It is completed and carried out an experimental measurement in the laboratory. The result shows that the sensitivity of the MNISBM meets the requirements of the measurement of near-infrared sky background level.

With the rapid development of wireless video communication and remote monitoring, the encoder is required to be low-complexity and low-power. Distributed video coding effectively reduces the complexity of encoder, since it shifts a majority of computation to the decoder. Frame interpolation is a key component of typical DVC system. It reconstructs the WZ frame based on the intra coded key frame, namely side information generation. The fewer differences between the side information and original WZ frame corresponds to the lower translating bit rate. In this paper, we carry out a new motion compensated interpolation based on non-uniform motion trajectory to refine the side information. Multiple reference frames is applied to fulfill our proposal. Testing results show that the proposed scheme improves the PSNR by 0.3-0.5dB in comparison with hierarchical block matching algorithm, and upgrades the rate-distortion performance in a certain degree.

Distributed video coding (DVC) is a new video coding paradigm that shifts the complexity from the encoder side to the decoder side. One particular case of DVC, the Wyner-Ziv coding scheme, encodes each video frame separately and decodes the video sequence jointly with side information. This paper presents a new Wyner-Ziv video coding scheme based on hierarchical block matching algorithm (HBMA). In this proposed scheme, the side information is greatly refined to assist the reconstruction of the Wyner-Ziv frames. The bidirectional motion estimation and the forward motion estimation are associated to generate the interpolated frame from temporally adjacent key frames to attain the high fidelity side information. During the bidirectional motion estimation, the size of the block and the search area vary at different levels of hierarchy. In additional, the motion vectors are inherited from big blocks to small blocks by choosing the smallest mean-of-the-absolute-difference value among neighboring blocks. Preliminary experiment results show that the proposed scheme can achieve better rate-distortion performance by 0.5-1 dB compared to the existing Wyner-Ziv video coding with the slightly increased decoding complexity.

The donor and the acceptor charges are arranged into the water with the interval. The donor charge has a cylindrical geometry with 30 mm diameter and 50 mm long. The acceptor has a disk form with 100 mm diameter and 10 or 5 mm thickness. Composition B is used for both of the donor and acceptor charges. The propagation processes of underwater shock waves from the top end of acceptor charge along the axis of charges are taken by the image converter camera under the intervals of 10, 15, 20 and 25 mm. In the case of 10 mm thick acceptor charge, the velocities of the underwater shock wave are the almost the same up to the interval of 20 mm. However, in the case of 25 mm the underwater shock wave has remarkable low velocity compared to the other cases. In the case of 20 mm interval, the velocity of the underwater shock wave in the case of the 5 mm thick acceptor is slower than that of 10 mm. Furthermore, the numerical simulations are conducted. The reaction rate law of the high explosive is a phenomenological model that is proposed by Lee and Tarver. The results of the optical measurement and numerical simulation demonstrate a good agreement.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

This paper presents the study on the application of explosive welding technique to the field of the urgent repair of the gas and water pipe networks. The essential parameters related to the explosive welding are scrutinized from the point of view of the minimizing the damage to the steel pipe after welded explosively with a flyer plate. The emulsion explosive is contained in a rectangular hard-paper box whose bottom is the flyer plate with 100 mm length, 25 mm width and 1.5 mm thickness. The flyer motions of the flyer plates accelerated by emulsion explosive are observed by high-speed photography from the side and front view of the flyer plate. The damage to the pipe by the flyer plate is discussed with the results of the observation of flyer motion and explosive welding test under various experimental conditions. Moreover, one way to control the motion of the flyer plate is proposed. We put a PMMA buffer block into the explosive. The flying process of flyer plate is calculated by the finite different scheme based on the ALE method. The effectiveness of this method is demonstrated by the experimental and numerical studies.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

On the common circumstances the detonation of explosives has a steady propagation rate and can be satisfactorily explained by Chapman-Jouguet's theory on this phenomenon. Hence, this type of detonation is more frequently called the Chapman- Jouguet (C-J) detonation. The detonation properties such as pressure, density, and temperature, of the detonation products are often characterized as the C-J values of the explosive that represent the corresponding maximums of the variables in the detonation products. However, when an explosive is initiated in some special ways, for instance, high velocity impact of a flyer plate, a strong detonation with properties higher than C-J values will be induced in the explosive. This strong detonation is what we called the overdriven detonation of explosive. The use of overdriven detonation expects to provide much more work to the surrounding matter than does the common C-J detonation. In order to have a basic knowledge of this detonation phenomenon, we designate an experimental set- up for the purpose of acquiring the overdriven detonation in high explosive. The set-up uses a circular metal plate accelerated by a piece of cylinder explosive (donor) to impact another cylinder explosive (acceptor), inducing a detonation wave in the acceptor explosive. The donor explosive used is PBX (85%wt HMX and 15%wt binder) explosive cylinder that has the detonation velocity of 7.84 km/s and the detonation pressure of 25.24 GPa and the acceptor explosive cylinder is SEP (65%wt PETN and 35%wt paraffin) with the detonation velocity of 6.97 km/s and the detonation pressure of 15.9 GPa. The impactor is the copper disc with the same diameter of the donor explosive and 1 mm and 2 mm thicknesses respectively. The detonations occurred in the acceptor explosive from the impact of copper flyer were recorded by the high-speed camera (IMACON 790). The photographs make us possible to estimate the detonation velocities from the distance and time data on them. In addition, we also make a numerical visualization on this phenomenon using a 2-D Lagrangian hydrodynamic code. The calculation, to somewhat extent, reproduces the consequences of the current experimental results.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.