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A Modified PDAF Algorithm For Measurement Covariances that Vary within a Time Scan |
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Written by Administrator
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Friday, 11 May 2012 05:50 |
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PROJECT TITLE : A Modified PDAF Algorithm For Measurement Covariances that Vary within a Time Scan ABSTRACT: This paper presents a modified version of the probabilistic data association filter (PDAF) algorithm for single target tracking which allows for measurement covariances to vary within, as well as between, time scans. This modification enhances the ability to track targets in situations where the measurement errors within a time scan are highly variable. The potential for improved tracking is demonstrated by comparing the performance of the modified and the standard algorithm in tracking simulated intensity detector measurements. |
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A Real Time EDAC System for Applications Onboard Earth Observation Small Satellites |
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Written by Administrator
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Friday, 11 May 2012 05:50 |
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PROJECT TITLE : A Real Time EDAC System for Applications Onboard Earth Observation Small Satellites ABSTRACT: Onboard error detection and correction (EDAC) devices aim to secure data transmitted between the central processing unit (CPU) of a satellite onboard computer (OBC) and its local memory. A follow-up is presented here of some low-complexity EDAC techniques for application in random access memories (RAMs) onboard the Algerian microsatellite Alsat-1. The application of a double-bit EDAC method is described and implemented in field programmable gate array (FPGA) technology. The performance of the implemented EDAC method is measured and compared with three different EDAC strategies, using the same FPGA technology. A statistical analysis of single-event upset (SEU) and multiple-bit upset (MBU) activity in commercial memories onboard Alsat-1 is given. A new architecture of an onboard EDAC device for future Earth observation small satellite missions in low Earth orbits (LEO) is described. |
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A Hierarchical Evolutionary Trajectory Planner for Spacecraft Formation Reconfiguration |
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Written by Administrator
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Friday, 11 May 2012 05:50 |
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PROJECT TITLE : A Hierarchical Evolutionary Trajectory Planner for Spacecraft Formation Reconfiguration ABSTRACT: A hierarchical evolutionary trajectory planner (HETP) for spacecraft formation reconfiguration is presented. Two levels are included in HETP. The high-level planner performs global planning which includes configuration optimization and collision avoidance between spacecraft. The low-level planners design multiple optimal or near optimal trajectories which are separated one from another for each spacecraft by parameterizing the controls in terms of Chebyshev polynomials. Based on the attributes of the system dynamics, a flexible scheme is used to select final trajectories and to avoid collisions. Our approach scales well with the number of spacecraft by planning trajectories for each spacecraft in parallel. The high level and the low level can coevolve, and multiple trajectories can be generated simultaneously as alternatives. The control precision constraints which could reduce control errors are also taken into account. The experiments described here demonstrate the efficiency of the proposed algorithm. |
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A Quaternion-Based Method for SINS/SAR Integrated Navigation System |
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Written by Administrator
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Friday, 11 May 2012 05:50 |
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PROJECT TITLE : A Quaternion-Based Method for SINS/SAR Integrated Navigation System ABSTRACT: A new quaternion-based method for the SINS/SAR (strap-down inertial navigation system/synthetic aperture radar) integrated navigation system is presented. This method overcomes the shortcomings due to the linear SINS error model used in the currently existing SINS/SAR integrated navigation systems. A quaternion-based matrix is derived for describing the attitude of SINS. Quaternion-based nonlinear error and observation models are established for the SINS/SAR integrated navigation system. An adaptive unscented particle filtering (UPF) algorithm is developed based on the quaternion-based nonlinear models for optimal data fusion in the SINS/SAR integrated navigation system. Experimental results demonstrate that the proposed quaternion based method can effectively reduce the navigation error and improve the navigational positioning precision. |
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Transponder Power Minimization Utilizing Optimum Channelizer Gains |
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Written by Administrator
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Friday, 11 May 2012 05:50 |
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PROJECT TITLE : Transponder Power Minimization Utilizing Optimum Channelizer Gains ABSTRACT: Today, the Wideband Global SATCOM (WGS) system employs a new concept of adjusting the transponder power gain of individual links. A simple optimum method is derived for selecting these individual channel gains to minimize the amount of transponder power utilized. This new method directly solves a set of simple nonlinear equations and does not utilize any search algorithms or matrix inversions thus allowing it to be used with any number of links in a transponder. |
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