Abstract: It is essential to save fuel in orbit control for micro/nano satellite due to the lack of resources. The  influences of control direction and control time on the relative ellipse semi-minor axis in in-plane companion-flying satellites were studied based on the Hill equation. Both theoretical analysis and simulation results show that the most efficient control method of relative ellipse semi-minor axis is to impose control parallel to the lateral direction on the top or bottom points while the control quantity |ΔV|≤nb/2 is certain and the relative ellipse semi-minor axis will change |Δb|=2|ΔV|/n at the same time.

Key words: In-planecompanion-flying, Hillequation, Ellipsesemi-minoraxis, Minimumfuelcontrol, Controltime, Controldirection, Micro/nanosatellite