Acquisition,Pointing and Tracking System for Shipborne Space Laser Communication without Prior Information

A space laser communication acquisition,pointing and tracking(APT)system based on the beacon laser is designed without prior information.And then,a new target scanning method and a pointing and tracking algorithm are proposed.The target scanning mode is the round-trip triangular wave scanning,and it means that scanning track of the PAN-TILT platform follows the triangular wave repeatedly.For the pointing and tracking algorithm,the beacon laser is used as the auxiliary aiming light source.The position of the beacon laser in the viewfield of the complementary metal oxide semiconductor(CMOS)camera is calculated by the centroid algorithm.In order to realize the target tracking,the joint control method of the angle control and the angular velocity control is used.The simulation and experimental results show that the APT system can achieve full coverage scanning in the scanning area and capture the target in one scanning cycle successfully.After capturing the PAN-TILT platform,the pointing and tracking algorithm can track the PAN-TILT platform quickly and accurately,and the tracking accuracy is up to 0.22 mrad.

Detection and Analysis of Strong Ionospheric Scintillation in Equatorial Region

To detect the occurrence of ionospheric scintillation in the equatorial region,a coherent/non-coherent integration method is adopted on the accumulation of intermediate frequency(IF)signal and local code,in the process of signal acquisition based on software receiver.The processes of polynomial fitting and sixth-order Butterworth filtering are introduced to detrend the tracking results.Combining with ionospheric scintillation detection algorithm and preset thresholds,signal acquisition and tracking,scintillation detection,positioning solution are realized under the influence of strong ionospheric scintillation.Under the condition that the preset threshold of amplitude and carrier phase scintillation indices are set to 0.5 and 0.15,and the percentage of scin-tillation occurrence is 50%,respectively,PRN 12 and 31 affected by strong amplitude scintillation are detected effectively.Results show that the positioning errors in the horizontal direction are below 5m approximately.The software receiver holds performances of accurate acquisition,tracking and positioning on the strong ionospheric scintillation conditions,which can provide important basis and helpful guidance for relevant research on ionospheric scintillation,space weather and receiver design with high performance.

Research on BeiDou anti-spoofing technology based on comprehensive radio determination satellite service

The BeiDou system(BDS)plays a significant role in people’s lives,but its security is easily affected by spoofing attacks.The radio determination satellite service(RDSS)is a special service of BDS that provides two-way communication,positioning,and timing services independently of the traditional radio navigation satellite service(RNSS).It can additionally be combined with RNSS to provide a comprehensive RDSS(CRDSS)service.In RDSS,after receiving a signal from the master station,the user needs to send a response signal back to the master station through a satellite.Therefore,the RDSS signal is difficult to spoof.In this study,based on the security feature of RDSS signals,an anti-spoofing method based on CRDSS is proposed to detect and mitigate spoofing attacks,verifying the advantages of the BeiDou system over other satellite navigation systems.