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Satellite Laser Ranging System And The Singal Correlation Detection At The Daytime

Posted on:2008-10-17Degree:MasterType:Thesis
Country:ChinaCandidate:X LiFull Text:PDF
GTID:2178360215452396Subject:Signal and Information Processing
Abstract/Summary:PDF Full Text Request
The principle of the satellite laser ranging (abbreviation is SLR) is that the interval of the laser pulse returned from the satellite multiplying by the speed of light obtains the satellite's distance. The satellite laser ranging principle although is simple But realizes actually extremely is difficult, completes the high accuracy survey needs the support of many kinds of technical, therefore its system is complex. But because daytime range background noise is very big, the return signal is very weak, and has other technical factors, at present has about fifty SLR stations in the world, and majority of only can work at night In the SLR application and research, the daytime range data has the important value. The opportunity of passing the observation station hasn't difference between daytime and at night. The daytime data will be helpful to precisely decides the satellite the axle, thus directly will affect the determination station coordinates and its change, and will affect the Earth dynamics other applied researches. Therefore all the countries attach importance to the daytime range work.Majority of satellite distance from 10,000 - 20,000 kilometers, even farther distance, return signal very weak, generally only has several to several dozens photons, most weak is only the single photon. So the early SLR system only can carry on the measure at night. Because background noise is very high at daytime, using the low pulse frequency carries on the satellite laser ranging in the daytime, the return points few, the acquisition's success ratio is low, harms to the person eyes. This project uses the high pulse frequency, the low pulse energy laser pattern for the first time, is safe to the person eyes, high reliability, and has more return points, is advantageous to the acquisition success ratio in the daytime. The return signal detection technology is high difficulty under the high pulse frequency.The paper has analyzed the satellite laser ranging system principle and the composition, as laser has high brightness, monochromaticity and the directivity, the people already apply it to the laser ranging. Satellite laser ranging system as a most important achievement, the system designs four major parts, the laser transmission subsystem, the laser receive subsystem, the turnplate servo subsystem, control and data processing subsystem. The laser produces pulse of laser after winding path of rays and Coude path of rays and introduces to send telescope. After send telescope right the laser beam and send satellite with the angular reflector. Meanwhile takes out the very small part of lasers in the laser, transforms after the photorectifier into the main wave sampling signal called the main wave pulse, after the pulse divider reshaping, as the gate signal or starts the signal, to start Event Timer to count the laser of sending to the satellite, returns to the ground after the angular reflector reflection, the received by the receive telescope, through the (C-SPAD) transformed into the electricity pulse, after the pulse divider reshaping,stop Event Timer to count. Such Event Timer recorded the time-gap counter between the main wave pulse and the return pulse, thus might figure out the distance from ground station to the satellite. Uses the high sensitivity photo detector may receive the weak photon signal, selects advanced SESAM lock mold semiconductor laser pump solid laser to take the vibration source. With the Event Timer high-speed record massive return signal, increased the system range precision. Uses the gate control technology to reduce noise. We may see from the simulation experiment that the gate width influence the false alarm probability, compression gate width may reduce the false alarm probability.The satellite laser ranging system contains many noises like background noise, the detector dark noise, the thermal noise and the quantum noise and so on. But the main noise is the sky background noise, in particular in daytime range. According to the radar ranging equation, and carries on the simulation computation, has produced Lageos, as well as this project measured three satellites (away from respectively 20000km, 30000km and 36000km) in view of the different peak angle situation, figure out the receive signal in the daytime. And the receive signal is only 0.38, the probability of detection is smaller than far from 90%, is unable to detect the return signal. Proposed uses the high pulse high repetition rate the signal to carry on the correlation detection, has analyzed under the high pulse frequency the signal correlation detection algorithm, and has estimated the night and the daytime intense noise false alarm probability and probability of success detection. Main question need to be solved is, under the condition of assigning the detection prob- ability and false alarm probability, to choose the best initialization correlation detection coefficient k namely the pulse integer to achieve the corre- late on detection under the certain detection probability, and the resident time of searching satellite namely the frame time TF value. Under the condition of the probability of detection (>90%), as well as the false alarm probability(<1%), analyzes the multi- pulses correlation detection algorithm, and according to the relations of correlation detection parameter between probability of detection and false alarm probability, through Matlab simulation determine the initialization correlation detection coefficient k and frame time TF.For detecting the laser pulse signal submerged in the noise, use the dual pho- toelectric detector to receive the laser pulse signal, then designed correlation dete- ction circuit according to the cross-correlation detection principle to process the received signal. This article analyses the noise and the pulse signal character- ristic, knows the signal and the signal itself correlation, but and the noise is not related, between the noise also is not related. According to the signal correlation and the noise random characteristic, process the signal; eliminate the noise, carries on the simulation through Simulink. According to the simulation, the result may determine that the signal correlation detection system may detect the pulse signal submerged in the noise.Using the high pulse frequency satellite laser ranging system still was for the first time in domestic. Analyzed the signal correlation detection algorithm and choose the best initialization correlation detection coefficient to complete the daytime ranging. This system took as the military project, has the important national defense significance. Establish a high level, high beginning, highly effective satellite laser ranging system. Make our country satellite laser ranging technology to a new level. This project development also has the important influence to our country satellite laser ranging research.
Keywords/Search Tags:satellite laser ranging(SLR), photoelectric detector, high pulse frequency, daytime ranging, detection probability, false alarm probability, correlation detection
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