Abstract: To address the need for efficient multi-target revisits in emergency Earth observation missions, this paper proposes a constellation design method that integrates subsatellite point trajectory analysis and grid search, based on the winning solution from the 13th China Trajectory Optimization Competition's Problem C. By examining the geometric properties of repeat ground track orbit, two target groups limiting coverage efficiency are identified, and sub-constellation division is employed to optimize coverage. Additionally, a 3-hour revisit timing sequence is designed based on the distribution of trajectory intersections, and the optimization space for maneuver planning is reduced by refining the initial orbits. Simulation results demonstrate that only eight satellites are required to meet the maximum revisit constraints of six hours for fixed targets and three hours for moving targets, while the total impulse consumption is optimized to 1927.39 m/s, offering a feasible solution for low-cost emergency constellation design.