In this paper, mission planning for an earth observation satellite is studied. Generally, the mission planning problem is known as a highly combinational problem. While exact methods can provide optimal scheduling solutions, they require large computation time so the exact methods may not be adequate for timely operations. In this paper, a simple yet effective heuristic method for mission planning is proposed. An additional degree of freedom in pitch axis is taken into account, which can significantly increase the number of images compared to the roll-only observations. Also, possibility of reverse order observation is considered with a simple objective function. The proposed method is applied to short-horizon mission planning in low earth orbit. The exact brute-force search is utilized as a counterpart to analyze optimality and time-effectiveness of the proposed method. Numerical results show that the proposed method offers a slightly degraded solution but runs very fast due to its simplicity.