The corner reflector is usually realized by fixing the corner cube prism through a specific structure, which is much easier to install and debugin practical application. As we all know, one of the most important uses of the corner reflector is that it can be used as a passive target marker for satellites and aircrafts. At a certain distance, as the angle of incidence increases, the return light efficiency of the corner reflector gradually decreases, and the return light efficiency directly affects the shape and brightness of the target point. Usually when multiple targets are tracked, the better the target direction consistency, the more uniform the light spot can be obtained. This paper introduces the method of drawing the normal direction of the corner cube prism to the mounting surface. The normal direction of the corner cube prism is tested by the self-collimating theodolite and the direction error is within 1′, and the error of return light efficiency is better than 5%, which provides high-precision pointing for the combination of multiple corner reflectors. On this basis, we expand the pointing design of the sub-corner cube prism for the plane array of the corner reflectors. After testing, the direction error of the sub-corner cube prism is within 5′.
In this paper, the photometric characteristics of passively marked corner-cube-reflector-class cooperative targets are studied. The imaging characteristics of corner cube reflector(CCR) are discussed theoretically, and the influencing factors such as surface accuracy, angle error and diffraction effect are analyzed. The reflection uniformity and diffraction characteristics of CCRs with different positions and different precision are simulated and verified. In addition, the influencing factors and control methods of CCR precision are proposed. To the photometric characteristics of cooperative targets, especially the influence of aperture size of cube-corner prism on comprehensive aberration, the transmission surface (bottom surface) on comprehensive aberration was concerned firstly, besides the three reflection surfaces. The conclusion was been drawn that the transmission surface and the three reflection surfaces had most effect on the parallel of emerging beams, and the minimum error was the minimum algebra sum of above four surfaces. It can provide theoretical support for on-orbit services such as companion flight, autonomous rendezvous and docking (RVD).
With the rapid development of modern optical detection technology, higher requirements are put forward for optical detection equipment. Whether it is a ground optical measuring instrument or a space detection camera, it is necessary to reduce or avoid the measurement performance degradation caused by the interference of strong light sources such as the sun.It briefly introduces the current application development of the sunshade deployment mechanism, comparatively analyzes some problems of the current application schemes, and proposes a design scheme of the ropes driven sunshade deployment mechanism. The traction of the constant pressure exhaust valve during the first deployment stage can be achieved by rope traction, which can quickly realize the air pressure balance between the target instrument to be sealed and the external environment, and can avoid the air pressure shock caused by the sealing failure in the initial deployment stage of the sunshade deployment mechanism; Rope traction can effectively control the speed of the unlocking process in the second stage of deployment, reducing the shock of the unlocking moment again; In the third stage of deployment, locking of the deployment joint can be achieved by rope traction, and locking backup can be effectively achieved. This kind of ropes driven sunshade deployment mechanism has the advantages of not only controllable deployment process, small shock, but can be used repeatedly without damaging or destroying the original deployment locking mechanism, and is especially suitable for ground measuring equipment and the ground repeated principle verification of space detection instruments.
High-voltage and ultra-high-voltage transmission cables are exposed to natural environment all the year round. Plastic and other non-metallic foreign bodies are often overlapped on cables, towers, insulators and other power grid facility, which leads to poor insulation among high-voltage power cables, and becomes one of the major threats to the normal operation of power systems. As a new light source, laser has a good application prospect in the removal of non-metallic foreign bodies such as polymers because of its high energy, strong monochromatic and good coherence. The use of laser to remove non-metallic foreign bodies such as plastics winding on transmission lines has the advantages of fastness, high efficiency, safety, so it has been widely used in the removal of foreign bodies in high-voltage and ultra-high voltage power lines. In this paper, the mechanism of laser ablation is analyzed and the optical system of laser ablation unit is designed. According to the actual situation of laser ablation of polymer for transmission line, the diameter of laser spot at 10-180m is determined to be 32mm. In the consideration of the error factors, the imaging quality of the optical focusing unit for the designed optical system is simulated. At the same time, the far-field characteristics of the laser are simulated and studied. The results show that the range of RMS SPOT radius change is less than the diffraction limit radius by sensitivity analysis of laser ablation unit considering errors. The designed optical focusing unit has good imaging quality and meets the requirements. With the increase of laser transmission distance, the diameter of laser spot increases slightly. The maximum spot diameter at 180m is 29mm, which is less than the design value. The designed optical system can meet the needs for laser ablation of polymer and has good effect.
The sources of stray light were briefly introduced and the necessity of stray light suppression was analyzed. Strong stray light often directly affected the performance of space debris detection camera and even invalidated it. Therefore, the application of stray light suppression in space debris detection camera was particularly important. The design of stray light suppression for space debris detection camera using baffle was proposed. On the basis of re-searching the source of stray light, the influences of the edge width of the baffle rings and the surfaces coating treatment scheme on the stray light suppression ability were finally determined. The stray light suppression ability of the baffle was greatly improved by exploring the limit of the mechanical processing of the baffle ring and optimizing the surface coating treatment method of the inner cavity of the baffle. At the same time, the stray light flow channel inside the optical system was optimized. The critical surfaces inside the optical system were found. After removing the critical surfaces, the stray light suppression design results showed the stray light rejection ratio reached 10-7 finally when off-axis angle was larger than 35°. The flares appearing on the detector disappeared completely in the experiments, and the signal-to-noise ratio was higher. The stray light suppression optimization obtained good results, which could better satisfy the requirements of space debris detection.
In order to meet the requirements of high-precision alignment of primary and secondary mirrors of space camera in
thermal environment, we develop a new supporting structure which can eliminate heat affect between mirrors
automatically. Through the simulation analysis, we have verified this structural design is feasible. According to
requirements of the optical system, an integrated machining scheme with three-bar supporting structure for the secondary
mirror is proposed. The automatic athermalization of the primary and secondary mirrors supporting structure is
confirmed by structural analysis and optimization. The displacement between the primary mirror and secondary mirrors
in the thermal environment range of -20° ~ +60°C is analyzed by using the PATRAN software, and the results show the
position change is within 0.01mm. The structural size of the secondary mirror supporting cylinder is optimized, and the
effect of stray light suppression for the multilayer sleeve visor is analyzed and verified by using the TRACEPRO
software. The results show that the proposed structural design can achieve the high stability of the primary and
secondary mirrors supporting structure and the good effect of stray light suppression.
The retroreflector array consists of multiple cubic corner reflectors, and is used as a cooperative target for space attitude measurement. The position and normal direction of each cubic corner reflector directly affect the measurement accuracy. From the point of view of structural design, a series of practical precision extraction methods are put forward based on machining accuracy in this paper. After the verification of some experiments, the accuracy of the method can be controlled within 5', and the position accuracy is better than 0.05mm.
In order to improve the stability of the secondary mirror mounting structure and reduce the influence of the position change of the secondary mirror on the imaging quality of the camera, the secondary mirror support structure was studied. Aiming at the problems of traditional secondary mirror support, a new type of secondary mirror bracket is proposed in this paper. The finite element analysis results show that under the same obstruction ratio, the torsional stiffness, the stiffness along the optical axis and the thermodynamic properties of the new secondary mirror bracket are similar to the secondary mirror traditional support structure, but the weight of the new s bracket is only 15.2% of the traditional support structure. The new bracket solves the shortcomings of the traditional secondary mirror support structure, such as high cost, long period and heavy weight, and is easy to assemble. It has been successfully applied in the all-day star orientation instrument.
The optical system of lunar rover navigation camera has a direct influence on imaging quality, and an indirect influence on the programming of march forward of lunar rover. One type of lunar rover navigation camera optical system with the symmetrical structure was introduced. It also set up the suitable position of stop to achieve the relative distortion lower than 0.053 percent under the 60 degrees wide field-of-view. It applied the hyperfocal distance principle to achieve the clear imaging from 0.5 meter to infinity. The modulation transfer function is close to diffraction limit at the Nyquist frequency (at standard object distance). Considering the complicate environment of lunar surface and the demand of exploration, it selected the appropriate work spectral coverage and was cooperated by the irradiation reinforce. As a result, it can bear 1×104 Rad (Si) space irradiation and is capable of keeping working normally in the severe environment with its temperature varying from -60°C to + 90°C.
A imaging system of area-array CCD cameras based on FPGA was designed. The overall structure and design of the system was introduced in detail. According to the working mode and driving timing requirements of this CCD image sensor, the driving schedule under the control of FPGA was designed. The working mode and parameters of such an imaging system were aligned with the control signals in accordance with the general requirements of space CCD cameras. With FPGA device as the platform of hardware design, the hardware of integrated timing and control system was described in VHDL language. The A/D converter AD9945 based on the correlated double sampling was used to realize the analog-digital (A/D) conversion of ICX285AL output signals. The XQR2V3000-4CG717V developed by Xilinx was chosen to accomplish the design of this hardware circuit. Through simulation, the correctness of driving schedule was verified, thus preparing necessary hardware for the final development of space area-array CCD cameras with high performance.
To reduce the surface deformation of a star tracker reflector in a complex and execrable environment, a micro stress flexible support structure was designed according to the circular optical reflector subassembly. By defining the thickness, width and radius as design variables, the flexible hinge in an circular reflector subassembly was optimized. Then, the surface figure precision, structural strength and dynamic stiffness of the reflector subassembly in the thermal-structural coupling state were analyzed with the finite element method. Simulation results show that the natural frequency of the reflector is enough, which has a sufficiently high dynamic stiffness. Both surface precision RMS of the reflector (8.34nm, 9.26nm) have reached the index requirements of the optical system (λ/10, λ=632.8nm) under gravity and uniform temperature change from -20℃ to 65℃. The results show that the design for the micro stress flexible support structure is reasonable and feasible, and achieves the design goal.
In order to realize real-time signal identification and processing of spatial transient light, the features and the energy of the captured target light signal are first described and quantitatively calculated. Considering that the transient light signal has random occurrence, a short duration and an evident beginning and ending, a photodiode detector based spatial transient light detection and processing system is proposed and designed in this paper. This system has a large field of view and is used to realize non-imaging energy detection of random, transient and weak point target under complex background of spatial environment. Weak signal extraction under strong background is difficult. In this paper, considering that the background signal changes slowly and the target signal changes quickly, filter is adopted for signal’s background subtraction. A variable speed sampling is realized by the way of sampling data points with a gradually increased interval. The two dilemmas that real-time processing of large amount of data and power consumption required by the large amount of data needed to be stored are solved. The test results with self-made simulative signal demonstrate the effectiveness of the design scheme. The practical system could be operated reliably. The detection and processing of the target signal under the strong sunlight background was realized. The results indicate that the system can realize real-time detection of target signal’s characteristic waveform and monitor the system working parameters. The prototype design could be used in a variety of engineering applications.
Space sensors are used in navigation sensor fields. The sun, the earth, the moon and other planets are used as frame of reference to obtain stellar position coordinates, and then to control the attitude of an aircraft. Being the “eyes” of the space sensors, Optical sensor system makes images of the infinite far stars and other celestial bodies. It directly affects measurement accuracy of the space sensor, indirectly affecting the data updating rate. Star sensor technology is the pilot for Space sensors. At present more and more attention is paid on all-day star sensor technology. By day and night measurements of the stars, the aircraft’s attitude in the inertial coordinate system can be provided. Facing the requirements of ultra-high-precision, large field of view, wide spectral range, long life and high reliability, multi-functional optical system, we integration, integration optical sensors will be future space technology trends. In the meantime, optical technologies for space-sensitive research leads to the development of ultra-precision optical processing, optical and precision test machine alignment technology. It also promotes the development of long-life optical materials and applications. We have achieved such absolute distortion better than ±1um, Space life of at least 15years of space-sensitive optical system.
High accuracy star map identification results are the basis of astronomical positioning. The traditional triangle star identification algorithm has a higher redundancy and a poor robustness to noise. Considering the specific requirements of the star map identification of the astronomical camera, in allusion to this default, proceeding with selection of guide stars, construction of guide star catalogue and realization of matching algorithm, a modified triangle algorithm based on traditional one is presented. With the proposed algorithm, the guide star is selected from astronomical durchmusterung. In order to speed up guide star indexing, the guide star catalogue is founded after dividing the sky using the overlapping rectangle method. The guide star sub-catalogue is constructed by the radius of guide triangle circumcircle and the two sides of guide triangle. The characteristic radius is used for indexing and sorted in an ascending order to improve the searching efficiency in the processing of star map identification. The matching scope of the angular distance is narrowed and the matching rate of angular distance is improved by the matching of the characteristics radius. If there exists redundancy, a normalized magnitude is used to eliminate it. Within the observing area of the real sky, the 1050 star maps continuously are calculated. The simulation results show that, the identification rate of this algorithm is greater than 97. 83% when the noise of position error is two pixels, and the average identification time is about 25. 07ms. Compared with the traditional triangle algorithm, this modified algorithm has a couple of advantages, including the smaller storage capacity of guide star catalogue, better robustness to position and magnitude error, higher rate of correcting star map identification and lower redundancy.
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