  Differential drag is a promising option to control the relative motion of
distributed satellites in the Very Low Earth Orbit regime which are not
equipped with dedicated thrusting devices. A major downside of the methodology,
however, is that its control authority is (mainly) limited to the in-plane
relative motion control. By additionally applying differential lift, however,
all three translational degrees-of-freedom become controllable. In this
article, we present a tool to flexibly plan optimal three-dimensional formation
flight maneuvers via differential lift and drag. In the planning process, the
most significant perturbing effects in this orbital regime, namely the J2
effect and atmospheric forces, are taken into account. Moreover, varying
atmospheric densities as well as the co-rotation of the atmosphere are
considered. Besides its flexible and high-fidelity nature, the major assets of
the proposed methodology are that the in-and out-of-plane relative motion are
controlled simultaneously via deviations in the yaw angles of the respective
satellites and that the planned trajectory is optimal in a sense that the
overall decay during the maneuver is minimized. Thereby, the remaining lifetime
of the satellites is maximized and the practicability and sustainability of the
methodology significantly increased. To the best of the authors knowledge, a
tool with the given capabilities has not yet been presented in literature. The
resulting trajectories for three fundamentally different relevant formation
flight maneuvers are presented and discussed in detail in order to indicate the
vast range of applicability of the tool.

Space Physics