جستجوی مقالات مرتبط با کلیدواژه « satellite constellation » در نشریات گروه « مکانیک »

Coverage of ground stations by satellites is a very important factor to access geographic, geotechnical and strategic information. This is generally achieved by one or more satellite with specified position and navigation. In this regard, in the area of low altitude orbits regional or global coverage of the Earth's surface is achieved utilizing various mathematical methods to change the position and arrangement of satellites. In this study, the arrangement of certain number of satellites is performed to reach maximum coverage. It is assumed that the satellite constellation is in the symmetrical Walker pattern. In this regard, taking into account the situation of user and determining the initial position of satellite in system, Geometric Dilution of Precision (GDOP) parameters are calculated utilizing a new model. The innovation in this new presented model is employing GDOP in an inverse manner. GDOP is a geometric standard that the less related values for it represents more accuracy in determining the amount of coverage. In this study the effects of compression of the earth as well as chamfer are considered. The calculations are presented for specific geographic areas and only for one day. The results show that by taking advantage of new computing model, the coverage area will dramatically increase. By organized employing of all the satellites in the constellation, with the best received Information from satellites, better coverage can be achieved.

For formation flying of two satellites in a satellite constellation, the relative motion and attitude determination algorithms are the key components that affect the quality of flight and mission efficiency. In this paper orbital relative motion of two satellites with arbitrary Keplerian elliptic orbit and in large distance will be analyzed and also exact and efficient solution for relative motion of the satellite with j2 perturbation which is one of the important perturbation in Low Earth Orbit (LEO) using spherical geometry is proposed. Direct geometric method using spherical coordinates are utilized to achieve this solution. In this method relative position and relative velocity of two satellites are calculated in the satellite constellation based on orbital elements. The obtained results from simulation with STK software, comparison of results with extracted results from equations for satellite with different eccentricity and analysis of the proposed method’s accuracy and fault show that the solution obtained from the geometric method presents the relative motion of the satellite with high accuracy. Thus, the proposed solution will be applicable and effective for relative motion of constellation satellites in space missions.

A novel approach is presented for the reconfiguration of satellite constellations based on Lambert’s theorem. The reconfiguration problem, in this article, is considered with the constraint of overall fuel cost minimization. Hence, orbital maneuvers required for the operation of reconfiguration is designed in such a way that, transferring the satellites to the desired configuration of constellation will be possible at minimal cost. Also, the introduced method of orbital transfer for implementing the reconfiguration phase of satellite constellation has no limitation on the shape and orientation of initial and target orbits such as: co-planarity, coaxiality, circularity and/or the existence of a common point. Moreover, a method is offered for modeling the cost function of reconfiguration problem in which the two important tasks of optimal orbital transfer of satellites to the target configuration of constellation and optimal assignment of each satellite to a specific terminal position or final orbit will be done in one single step. For this purpose and in order to achieving the globally optimal solution of the reconfiguration problem of constellation the hybrid PSO/GA is used. Finally, two different scenarios of reconfiguration of satellite constellation will be modeled once by the presented approach and once by considering determined positions of flight and deployment for the satellites. The obtained results indicate the superiority of the idea presented in this article.