Abstract:A high-precision solar sensor specially used for image stabilization systems of solar-observing is designed. In view of the shortcomings of traditional four-quadrant solar sensors, a detector based on cross-type silicon photovoltaic solar cells is designed in order to improve the sensitivity and anti-jamming capability of the sensor. The sensor has a low error of 10 arc seconds in the effective field of view (1°).

Abstract:To detect the concentration of greenhouse gas in the atmosphere of the earth, four kinds of gas detection optical systems with the spatial resolution of 2 km, the ground swath of 500 km and the orbit altitude of 690 km are designed. The central wavelengths of the four wavebands are 1.606 μm (weak CO2), 1.660 μm (CH4), 2.064 μm (strong CO2) and 0.765 μm (O2) respectively. Their spectral resolutions are 0.08 nm/20000, 0.08 nm/20000, 0.1032 nm/20000 and 0.045 nm/17000 respectively. The whole system consists of an immersed plane diffraction grating, a Littrow optical structure and a front optical system. Its Modulation Transfer Function (MTF) at the Nyquist frequency is close to 80% and the diffraction energy in a single pixel size is close to 90%. So, the system can be used to implement hyper spectral detection.

Abstract:A spaceborne Visible light camera imaging simulation system based on OpenGL is presented. It is mainly used to simulate the scenes when the spaceborne visible light camera is observing other space objects and output simulation images. The simulation system not only can provide image data for space object detection and tracking, but also can provide technical support for the design and performance evaluation of spaceborne cameras. The 3ds Max software is used to establish the precise three-dimensional model for a space object and vest it with material properties. The satellite Toolkit is used to predict the orbital parameters of both the space object and the camera. The star catalog is used to provide the parameters such as the position, magnitude and proper motion of a star against the starry background. In the Open Graphics Library, the scenes when the spaceborne visible light camera is observing a space object are established and the observing effectiveness of the spaceborne visible camera is simulated. The result shows that the simulation system has its higher simulation degree and rendering speed. It can be used to implement the rendering of the observing imaging effectiveness of both point objects in deep space and short distance area objects in real time.

Abstract:A 2 to 14 μm ambient infrared spectroradiometer based on linear variable filters with spectral resolution of 2% measurement wavelength is studied. According to the wavelength range limit of a single slice gradient filter, the coverage of the 2 to 14 μm wide band is realized by combining three pieces of variable filters with a spectrum fusion algorithm. By using a scheme containing a fine stepping motor and a position sensor to carry out fine spectrum splitting, the spectral resolution of 2% measurement wavelength is realized. By using the chopping and digital orthogonal lock-in amplifier scheme, the detection of weak infrared spectral signals is realized. For a stepping motor used to drive variable filters, the approximate function control algorithm and step frequency conversion acceleration motion law are used. Thus, fine step control and 0.1scan/second to 10 scan/second variable spectrum scanning speed are achieved. Finally, the calibration method and result of the spectroradiometer are presented.

Abstract:A laser echo digitizing system based on a new switched capacitor array technology was designed. By using the system, the sampling rate of 5 Gigabit samples per second was achieved. Multichannel sampling was realized by using a single chip analog digital converter. The system had a great potential for development. A laser echo digitizing circuit based on DRS4 chips was designed, a laser testing system was built and the signal sampling experiment based on DRS4 chips was carried out. The results showed that the laser echo digitizing circuit could obtain a sampling rate of 5 Gigabit samples per second, could realize multichannel sampling, could increase the field of view and could reduce the power consumption and cost of the system.

Abstract:Space exploration missions require cryocoolers to provide cooling power in different temperature regions. The two-stage high frequency pulse tube cryocooler is a potential solution. A thermally coupled two-stage high frequency pulse tube cryocooler is presented. To improve the compactness, its two cold fingers are both shaped in coaxial type. The no-load temperature of 22.03 K is achieved in the phase shifting with only a room temperature inertance tube. For a total input electric power of 413 W, both 8 W@80 K and 1 W@30 K can be obtained at two stages. Experimental study is carried out for its cooling performance at different precooling temperatures. The changing rule of the efficiency of cold fingers at low temperature stages is obtained.

Abstract:To use a free warm piston instead of both an inertance tube and a buffer as the phase shifter of a Pulse Tube Cryocooler (PTC) not only can reduce the volume of the phase shifter, but also can improve the performance of the PTR. To study the influence of the free warm piston on the performance of the PTC, a free warm piston PTC is designed and studied experimentally. The results show that for a constant input power, when the working frequency increases, the displacement phase difference between the compressor piston and the free warm piston increases and the swept volume ratio of the compress piston over the free warm piston increases. When the charging pressure increases, the displacement phase difference increases and the swept volume ratio decreases. The results are of great significance to the design and optimization of free warm piston PTCs.

Abstract:An Indium Arsenic Antimony (InAsSb) thick film single crystal grown by new technology was presented. With this material, a highly sensitive uncooled photoconductive detector was made by using the same process as that of room temperature InSb detectors. The photoelectric properties and spectral responsivity of the detector were measured and compared with those of the room temperature InSb detector, the cooled InSb detector and the PbSe detector. The obtained data provided a reliable basis for the wider application of InAsSb detectors operating in the mid and long infrared waveband (5-12 μm).