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.
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.
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.
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.
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.
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.
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.
KEYWORDS: Sensors, Observatories, Calibration, Black bodies, Near infrared, Indium gallium arsenide, Temperature metrology, Signal to noise ratio, Infrared radiation, Electronics
The Ngari (Ali) observatory is located in Ngari, Tibet, a region known as “the roof of the roof of the world.” The observatory benefits from abundant photometric nights, low perceptible water vapor, high transmittance, and good seeing. Due to these advantages, it promises to be one of the best locations in the world at which to make infrared and submillimeter observations. However, no data on the sky background radiation at this location are available, impacting the planning of future facilities at the observatory. To remedy this deficiency, a near-infrared sky brightness monitor (NISBM) has been designed to obtain data in the J, H, and Ks bands. This monitor is based on an InGaAs photoelectric diode and uses chopper modulation and digital lock-in amplifier processing, which considerably enhance its signal-to-noise ratio, detectivity, and data acquisition speed. An independent device has been designed for each band (J, H, and Ks) and calibrated in the laboratory. The NISBM was installed at the Ngari observatory in July 2017 and has obtained the first NIR sky brightness data for that location.
KEYWORDS: Telescopes, Imaging systems, Control systems, Control systems design, Astronomy, Web services, Optical filters, Interfaces, Optical instrument design, Charge-coupled devices
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.
Tibet is known as the third pole of the earth. The Ngari (Ali) observatory in Tibet is a good site, and promising to be one of the best place for infrared and submillimeter observations in the world. However, there is no data available for sky background brightness in such place. In the near infrared band of J, H, Ks, a NIR sky brightness monitor (NISBM) is designed based on InGaAs photoelectric diode. By using the method of chopper modulation and digital lock-in amplifier processing, the SNR (Signal Noise Ratio), detectivity and the data acquisition speed of the device is greatly improved. The NISBM has been installed in Ngari observatory in July of 2017 and obtained the first data of NIR sky brightness at Ngari observatory.
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 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.
KEYWORDS: Camera shutters, HVAC controls, Detection and tracking algorithms, Telescopes, Control systems, Field effect transistors, Stars, Temperature sensors, Astronomical telescopes, Cameras
A heating system for the mechanical shutter for the Antarctic Bright Stars Survey Telescope (BSST) is introduced. The system consists of a thermal insulation shutter house and a heating control box. The key design of the thermal-insulation shutter house is introduced. The heating control algorithm based on fuzzy-proportional–integral–derivative is designed to improve the performance of the system. A secure control algorithm for power MOSFET is necessary in extremely cold environments. The system has been tested in the cryogenic environment for 4 weeks, which proved that the heating system has the characteristics of low temperature adaption, high accuracy of the temperature control, remote operation, and detection. As a part of the BSST, the system has been running successfully for over half a year at Zhongshan Station, Antarctica.
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