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.
The Antarctic Plateau is one of the best places for infrared and submillimeter observations in the world, which has the advantages of high altitude, low water vapor and low atmospheric thermal radiation. It is indispensable for the design of instruments to know the environment of the observatory site in advance, especially the infrared sky background brightness. It determines the ultimate magnitude of infrared observation of the equipment, which is an important reference to evaluate whether a candidate site is suitable for constructing corresponding equipment. We have designed a NIR sky brightness monitor (NISBM) based on InGaAs photodiode, which is used to monitor the J, H and Ks bands of sky background brightness at the Dome A. In the Ks band the signal is sensitive to thermal radiation and temperature fluctuations. So, it needs to be calibrated in real time by a surface source blackbody. According to this requirement, we have designed a surface source blackbody that has the property of low temperature resistance, high emissivity, and high temperature uniformity. The device has a compact structure. The control system and the radiation surface are packaged in the same square house, which is suitable for outfield installation and calibration with low ambient temperature.
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 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.
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.
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 infrared sky brightness level is an important parameter for infrared astronomical observation from the ground. It is necessary to obtain the infrared sky brightness level at an observatory site to evaluate the feasibility of infrared telescopes and instruments. In order to evaluate the possibility of developing infrared astronomical observations at several sites in China, the design of a continuous-scanning near-infrared sky brightness monitor (CNISBM), measuring 2.5 to 5 μm infrared sky brightness based on an InSb detector and a linear variable filter, is proposed. The optics and the detector were put in a vacuumed cryogenic dewar to reduce the background emission. The CNISBM has been tested by measuring the flux intensity of the observing window in the L-band. The results show that the sensitivity of CNISBM satisfies the requirements of the observations of 2.5- to 5-μm near-infrared sky brightness.
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 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.
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 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.
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 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.
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.
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 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- 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.