The performance of the camera is a decisive factor in astronomical observations. The scientific CCD fits this need. In order to realize remote control of CCD camera and obtain its performance parameters, a test platform of a scientific CCD camera is built. The test parameters include gain, noise, linearity, full well capacity test, crosstalk test, dark current test. At present, our test platform has carried out multi-group tests of gain, noise, full well and linearity by connecting with a CCD scientific camera. In this paper, a remote control system of the test platform is designed using WEB technology and EPICS, which is convenient for test operators.
KEYWORDS: Cameras, Control systems, Imaging systems, Control systems design, Databases, Web services, Local area networks, Data storage, CCD image sensors
In order to meet the requirement of scientific camera system with remote control, a set of distributed remote control system is built based on EPICS framework and Web service for a camera system. EPICS provides an implementation framework of distributed soft real-time control system based on Channel Access protocol. A single device control program is named IOC. It's convenient to monitor and maintain the status of devices by operating the interfaces of IOC program, namely Process Variable (PV). This paper mainly discusses the IOC implementation of CCD controller, ion pump controller, vacuum pressure sensor and temperature controller, as well as the construction of Web monitoring platform based on Quasar and Flask framework. At present, the remote control system has been put into CCD290-99 camera named PXE290.
A telescope has been an important way to observe the stars since it was invented. With the development of the times, people have higher and higher requirements for telescopes. In order to further improve the imaging quality and observation accuracy, the aperture of the telescope is becoming larger and larger, the associated devices are becoming more and more complex, and the working environment is becoming more and more diverse. A good telescope control system can effectively reduce labor costs and improve the utilization efficiency of observation time, so people put forward higher requirements for telescope control system. The emergence of computers has promoted the rapid development of a control system for a telescope system. Faced with the development trend of large-scale, networked and diversified observation requirements of telescopes, the control system realizes robustness and scalability on the basis of automatic observation. In this paper a control system for a telescope system based on RACS2 framework is introduced. This control system includes front-end services, back-end services, observation control components and device components. The device components are designed, which is responsible for interacting with the devices such as a telescope mount, a camera and a weather station. The remote control is realized based on Web service. The observational operation of the telescope system is tested with good results.
The wide field survey telescope (WFST) is a new generation survey telescope that is being built in China. Its optical design is a primary-focus system, and its camera is a mosaic charge-coupled device (CCD) camera composed of nine 9 K × 9 K CCD290-99 chips for scientific imaging. A verification platform to test the CCD290-99 chips is designed. The test platform includes a light source system, CCD controller, vacuum Dewar, and refrigerator for cooling the CCD. The CCD controller is a prototype design of the WFST camera that has a high performance, including low readout noise, flexible readout rate configuration, low power dissipation, etc. The digital double correlated sample method is used for video sampling of the CCD’s 16 channels. The specifications of the CCD detector system using a CCD290, such as gain, noise linearity, and crosstalk, are tested using this platform. The test results show that the CCD test platform meets the requirement of the CCD test and the design of CCD controller meets the scientific imaging requirements for the WFST camera.
KEYWORDS: Databases, Optical instrument design, Astronomical telescopes, Telescopes, Local area networks, Process control, Visualization, Observatories, Control systems, Automatic control
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.
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.
Many specs of scientific CMOS cameras characterize the performance of camera, which can help developers analyze the quality of cameras. In order to test the performance of sCMOS cameras, we designed and built a test platform for performance test of sCMOS cameras which has been developed. The test platform includes a group of test devices and a automatic test software system. The software system is designed based on remote controllable WEB technology and EPICS-based real-time control framework, making the test platform flexible and convenient. According to the features of sCMOS camera, in the test platform four test procedures are designed to test various specs of sCMOS camera, including FPN test, dark current test, gain, noise, linear error, full well capacity test and dead pixel test. Users can perform automatic tests on camera through web UI, including the control of test platform device, data acquisition and data processing. At the same time, the test platform also provides users with various functions such as test data query and test report generation.
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.
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.
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