Deployment strategy for satellite-sail transverse formation

In the general 2-satellite formation near Earth, the deputy satellite moves around the chief one, resulting that the relative baseline exhibits the periodical variations in the form of trigonometric functions. In such case, only the certain positions can be employed for interferometric imaging, and the high requirements of Earth observation and remote sensing can be barely satisfied. Therefore, a new tethered satellite-sail system, termed satellite-sail transverse formation, is proposed in this study. The chief satellite is in a sun-synchronous orbit and is connected to one deputy solar sail in a non-Keplerian displaced orbit. Given the continuous solar radiation pressure, the sail can move with the satellite side by side synchronously such that the relative baseline is always perpendicular to the subastral point tracks of the satellites. Our investigation mainly focuses on the relative dynamics and control of the proposed system during the deployment process that is divided into two stages: pop-up and steady release. Subsequently, the deployment dynamics are established considering the chief and deputy satellites as mass points connected by a rigid rod. To ensure a successful deployment, a sliding mode controller with a saturation function is adopted where the control force is provided by the solar radiation pressure and tether tension. The results show that the proposed deployment strategy is successful, and the transverse formation is eventually realized under the smooth rotation of the solar sail.