Study On Location Method Suitable To ATP System For Deep-space Laser Communication

It is a very potential way to use laser to return scientific data to earth in the exploration of deep space, but it faces great challenges to maintain high-precision pointing of optical transceivers on both ends of a communication link. Under this circumstance, traditional ways of tracing localization have ceased to be effective. Therefore, it is of great significance to study on the ways of tracing localization which is applicable to the ATP for deep-space laser communication.Based on the research into various traditional methods, the earth image is selected as the tracking beacon, according to the ATP's characteristics of laser communications used in the deep-space exploration. A new method is put forward on the basis of DTF and the relevant macro-pixel of maximum likelihood estimation, with which the target areas on earth image can be determined through macropixels method, and then the target positon are to be gained by making use of DTF and maximum likelihood estimation in the target areas.The thesis defines the concept of valid pixel ratio and analyzes what effect the noise has on confirming the target region of earth image. Finally, we can obtain the smallest macro-pixel and the restricted operation for determining the target of macro-pixel. For earth image of 512 pixels×512 pixels, the target is about 16×16 pixels in size. The most macropixels is 36 pixels and target macro-pixel is enlarged by 2 pixels. The value of r is 1 when SNR is 5dB. To get the precise location of earth target, we have adopted DTF and the maximum likelihood estimation. This method calculates the translation of earth beacon signals, so a nonlinear equation is needed solving. The linearly approximated result shows that the total translation error is below 0.5 pixel. The translation error in X direction is 3.2% and in Y direction is 2.75%. When SNR(Signal Noise Ratio) is 1 and the size of beacon image is closer to reference image, the center position of beacon image calculated are almost the same as the actual ones of beacon image.The experimental results show that the maximum error is 0.115urad by applying DTF and the relevant macro-pixel of maximum likelihood estimation, and that it can completely meet the need of acquisition.