Orbit design and estimation for surveillance missions using genetic algorithms

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Title: Orbit design and estimation for surveillance missions using genetic algorithms
Author: Abdelkhalik, Osama Mohamed Omar
Abstract: The problem of observing a given set of Earth target sites within an assigned time frame is examined . Attention is given mainly to visiting these sites as sub -satellite nadir points . Solutions to this problem in the literature require thrusters to continuously maneuver the satellite from one site to another . A natural solution is proposed . A natural solution is a gravitational orbit that enables the spacecraft to satisfy the mission requirements without maneuvering . Optimization of a penalty function is performed to find natural solutions for satellite orbit configurations . This penalty function depends on the mission objectives . Two mission objectives are considered : maximum observation time and maximum resolution . The penalty function poses multi minima and a genetic algorithm technique is used to solve this problem . In the case that there is no one orbit satisfying the mission requirements , a multi -orbit solution is proposed . In a multi -orbit solution , the set of target sites is split into two groups . Then the developed algorithm is used to search for a natural solution for each group . The satellite has to be maneuvered between the two solution orbits . Genetic algorithms are used to find the optimal orbit transfer between the two orbits using impulsive thrusters . A new formulation for solving the orbit maneuver problem using genetic algorithms is developed . The developed formulation searches for a mini mum fuel consumption maneuver and guarantees that the satellite will be transferred exactly to the final orbit even if the solution is non -optimal . The results obtained demonstrate the feasibility of finding natural solutions for many case studies . The problem of the design of suitable satellite constellation for Earth observing applications is addressed . Two cases are considered . The first is the remote sensing missions for a particular region with high frequency and small swath width . The second is the interferometry radar Earth observation missions . In satellite constellations orbit's design , a new set of compatible orbits , called the "Two -way orbits" ,whose ground track path is a closed -loop trajectory that intersects itself , in some points , with tangent intersections is introduced . Conditions are derived on the orbital elements such that these Two -way Orbits exist and satellites flying in these orbits pass the tangent intersection points at the same time . Finally , the recently proposed concept of observing a space object from onboard a spacecraft using a star tracker is considered . The measurements of the star tracker provide directions to the target in space and do not provide range measurements . Estimation for the orbit of the target space object using the measurements of the star tracker is developed . An observability analysis is performed to derive conditions on the observability of the system states . The Gaussian Least Squares Differential Correction Technique is implemented . The results obtained demonstrate the feasibility of using the measurements of the star tracker to get a good estimate for the target orbit within a period of measurements ranging from about 20 percent to 50 percent of the orbital period depending on the two orbits .
URI: http : / /hdl .handle .net /1969 .1 /3126
Date: 2006-04-12


Orbit design and estimation for surveillance missions using genetic algorithms. Available electronically from http : / /hdl .handle .net /1969 .1 /3126 .

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