Dynamics and Control for Transverse Formation by a Distributed Drag Sail

The constant effective vertical measurement baseline provided by the transverse formation satellites in low orbit has a critical application prospect for ground and high-orbit target detection. However, traditional formation satellites decay owing to atmospheric perturbation, and their effective baseline is periodically time-varying. A distributed drag sail (DDS) with several louvered subsails is promoted based on the free molecular flow theory, which allows for high maneuverability in satellite-tether-sail (STS) transverse formation flying. Moreover, the fuzzy proportion differentiation (PD) control is introduced into the attitude-orbit model, which attains the time-dependent PD coefficients based on the geometrical configuration, to handle coupled attitude-orbit of the DDS. The aerodynamic force vectors are distributed geometrically in a bounded two-dimensional area with a pentagonal shape, through different twist combinations of subsails. The size of the distributed area depends on the number of subsails, the length, and the width of DDS. Finally, it is achieved that the steering engines of DDS can work effectively in appropriate frequencies during the stable formation configuration. Binocular detection with a constant vertical measurement baseline can be provided by DDS to gain situational awareness of space targets in practical scenarios such as remote sensing applications.