This paper addresses the problem of designing suitable satellite constellations for Radio Occultation missions. Radio occultation for the Earth atmosphere usually requires global coverage and short interval measurements. The 2-D Lattice Flower Constellations theory is here applied to design constellations in order to maximize active time by providing global coverage with frequent measurements. Optimizations are performed using Genetic Algorithms to estimate constellation design parameters. Optimization is constrained by altitude range (to limit atmospheric drag and avoid Van Allen belts) while orbit nodal precession is used to obtain global coverage. The resulting constellation geometries have been explored from coverage performance perspective. Two coverage estimation methods have been used to evaluate coverage performances. Performances of some solutions are provided to makeoptimality selection.