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-<sub>rms</sub>. 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 2.5~5um infrared band is an important waveband in infrared astronomy research. Infrared sky brightness monitoring is an important part of ground-based infrared astronomical observations. The measurement of infrared sky brightness and the characteristics of the infrared observation conditions of an area, especially the average intensity and variation parameters of infrared radiation will provide an important reference for future design of infrared telescopes and other observation instruments. We designed a sky brightness spectrograph for 2.5-5um continuous infrared spectroscopy using an InSb detector and conduct a test measurement of the sky brightness radiation intensity with L band whose center wavelength is 3.77um.
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.
The wide field survey telescope (WFST for short) is a new generation survey telescope located in Lenghuzhen, Qinghai Province in China, and has outstanding performance in sky survey. However, the feature demands a rigid flatness 20μm PV of the prime focus plane of the prime focus camera. The CCD290-99 flatness 15μm PV and -100°C working condition pose challenges to the CCD splicing. In order to verify the CCD mosaicing technology for WFST’s prime focus camera before the sensor arriving, we use the CCD 303-88 in our lab to set up the verification platform. In this article, we mainly introduce the recent research status of the platform.
<p>A 1 k × 1 k CCD camera is designed, implemented, and tested for the CSTAR2 telescope in Antarctica, including its mechanics, CCD controller, and low-noise power system. In the design of mechanics and electronics, low-temperature environment is taken into full consideration. The camera has demonstrated mechanical and electrical stability. The system readout noise is as low as <inline-formula><mml:math display="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>3.99</mml:mn><mml:mtext> </mml:mtext><mml:msubsup><mml:mrow><mml:mi mathvariant="normal">e</mml:mi></mml:mrow><mml:mrow><mml:mi>rms</mml:mi></mml:mrow><mml:mrow><mml:mo>−</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math></inline-formula> when the CCD readout frequency is 100 kHz. Every part of the camera is fully tested in a cryogenic refrigerator (−86 ° C) and proved that the camera has the ability to work in Antarctica for a long term. Finally, the camera is installed on the CSTAR2 telescopes to take observations and the imaging function is well implemented.</p>
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.
In order to implement the driver and readout functions for several types of scientific CCD detector, meanwhile decreasing the size of electronics and reducing the total power dissipation for a large scale mosaic CCD detector system, two Application-specified Integrated Circuits (ASIC) were designed. One is for CCD driver and called BCDA (Bias Clock Driver ASIC), which is to provide multi-channel clocks and Bias voltage; the other is for CCD video processing and called CVRA (CCD Video Readout ASIC). In the BCDA chip, the bias drivers are generated by high voltage amplifiers. The clock drivers are made of a clock switch circuit and high voltage amplifier. Two 8-bit current-steering DACs are used to adjust the driver capability and high-level voltage of clocks. The CVRA chip processes the video signal of a CCD detector. The functions of CVRA chip consist of pre-amplifier, single-to-differential circuit, CDS circuit, and integrating circuit. The Global Foundry 180 nm BCDlite technology is used in this chip design. The first round of design has been finished and part of tests of two chips have been done.
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.
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.
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 3.99݁ି 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.
In a CCD camera system, the CCD sensor must be cooled to low temperature to reduce the dark current. Many factors will affect the cooling performance as we use TEC. Therefore, quantitative analysis of the effects of the various factors on the cooling performance is very important for designing the cooling structure of the CCD vacuum head. In this paper, the length and diameter of the wires between the CCD and the vacuum feedthrough, the thickness of the cold end, and the vacuum degree are taken into consideration and analysis. Through the simulation, useful conclusions are obtained to guide the machanics and cooling design of the CCD vacuum head.
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.
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.
A prototype of scientific CCD detector system is designed, implemented and tested for the extreme environment in Antarctic, including clocks and biases driver for CCD chip, video pre-amplifier, video sampling circuit and ultra-low noise power. The low temperature influence is fully considered in the electronics design. Low noise readout system with CCD47-20 is tested, and the readout noise is as low as 5e<sup>-</sup> when the CCD readout speed is 100kpixs/s. We simulated the extreme low temperature environment of Antarctic to test the system, and verified that the system has the ability of long-term working in the extreme low temperature environment as low as -80°C.
A heat preservation system for mechanical shutter in Antarctic is introduced in the paper. The system consists of the heat preservation chamber, the host controller STM32F103C8T6 with peripheral circuit and the control algorithm. The whole design is carried out on the basis of the low temperature requirement, including the cavity structure and thermal insulation. The heat preservation chamber is used to keep the shutter warm and support the weight of the camera. Using PT100 as the temperature sensor, the signal processing circuit converts the temperature to the voltage which is then digitized by the 12 bit ADC in the STM32. The host controller transforms the voltage data into temperature, and through the tuning of the Fussy PID algorithm which controls the duty cycle of the MOSFET, the temperature control of chamber is realized. The System has been tested in the cryogenic environment for a long time, with characteristic of low temperature resistance, small volume, high accuracy of temperature control as well as remote control and detection.
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.