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Orbit Design and Optimization of Satellite Constellation for Regional Coverage

Borhani, Amir | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 45367 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Assadian, Nima
  7. Abstract:
  8. In this thesis, the satellite constellation orbit design for regional coverage is investigated. The orbits of satellites in a constellation for Earth observation missions play a crucial role in performance and characteristics of the mission; for example the image resolution, the area of coverage, and the coverage interval. In this thesis the problem is to find the optimal initial orbital elements for meeting the earth observation mission objectives for one or several sites. The cost functions are the total coverage time, the maximum gap time, time average gap, altitude, and number of satellites. The problem is solved in a multi-objective manner for different combination of two of the above functions. The number of satellites between two and six are examined. In the previous works, the discrete simulation technique is employed to calculate the sites coverage times. The main drawbacks of this technique are the low accuracy and huge computation burden. Therefore, a new, fast and precise algorithm for calculating satellite coverage time is developed in this thesis. This algorithm is based on secant method in finding the start and final times of coverage. Thus, there is no need to check the coverage in many excessive time steps. Moreover, the coverage times can be computed with high accuracy and is not constrained to the discretization time steps. A new algorithm for computing the union of the coverage times of several satellites over a site is also introduced. The multi-objective Genetic Algorithm (controlled NSGA-II) is used for optimizing cost functions. The various combinations of satellites, orbit repeat cycles, different sites around Iran, and Sun-synchronous constraint have been studied. The results showed that the Iran region can be covered with maximum gap of near 2 hours by using 5 satellites in the LEO orbits with the apogee of less than 700km
  9. Keywords:
  10. Orbit Design ; Reginal Coverage ; Satellite Constellation ; Earth Observation

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