The problem of providing continuous coverage of portions of the earth's surface by means of polar satellite networks is considered, and an optimum arrangement is proposed in which the motion of satellites in one orbital plane is synchronized with that of the satellites in adjacent planes. Relations are developed between the numbers of satellites, their relative positions, and the required minimum latitude of continuous coverage. The method of solution of these relations is outlined, arid an example is presented. The resultant number of satellites required for this case as a function of altitude is compared with the number required for a symmetric, nonsynchronous set of satellite orbits.

Global positioning by means of satellites requires simultaneous observation by at least four satellites. The problem is to determine the minimum number of satellites and the corresponding orbital geometry necessary to satisfy this requirement on a continuous basis. To model the problem, a fixed number of users are assumed uniformly distributed in a known manner over the surface of the earth, and the satellites are restricted to exist in either three or four orbital planes. However, the orbit radius and inclination angle are left as variables. Under these assumptions, and starting with a small number of satellites which will be increased afterwards, an algorithm is developed to determine the visibility of satellites at each surface location. In this way it is possible to specify the minimum number of satellites needed by any desired orbital geometry. It is found that the number of satellites required for three-dimensional continuous worldwide coverage decreases as the orbit radius is increased. There appears to be no general trend regarding the effect of the inclination angle on the minimum number of satellites.

A novel constellation of low earth equatorial orbit (LEQ) satellites is proposed to provide continuous coverage for countries with maximum latitude limit of plusmn25deg. Analysis and computer simulation results show that for such coverage with a minimum elevation angle of 10deg, a maximum number of 16 LEQ satellites is required. The analysis presented in this paper is applicable to geographical locations within the given maximum latitude limit on the earth

As Low-Earth Orbit (LEO) satellite deployments scale to thousands of nodes, the design of satellite network topologies becomes increasingly complex yet critical for achieving the desired performance. Since each LEO satellite can only provide service to a small area on the ground, inter-satellite communication and sophisticated networking are required to achieve the best performance. Differing application-specific performance metrics and associated trade-offs can drive changes to topology design that optimize for specific use cases. However, satellite constellation topology design is not amenable to traditional optimization methods, such as linear programming, due to the complex interactions between different design parameters, especially as the number of satellites in the constellation grows. In this paper, we propose the Multifaceted Optimized Satellite Constellation Topology (MOST) framework, a framework that optimizes across multiple arbitrary performance metrics when creating a satellite constellation network topology, allowing a constellation designer to tune the network topology for specific applications. This framework is then solved using the proposed MOST algorithm, a cubic complexity algorithm that optimizes across the selected metrics. We present the LEO Approximate Minimum Propagation Delay, Up Time (LAMP-UP) topology, a topology produced with the MOST algorithm that optimizes for low latency and high link uptime. This topology is evaluated under different traffic

applications (Landsat) satellites which provide imaging data of the Earth . The team focused on the development of an integrated, user-oriented, Earth -sensing information