An Investigation On The Optimization Maneuver Technique Of Ground Track Adjustment For Responsive Missions

In recent years,with the development of the operationally responsive space technology and the increasing space missions,more and more researches have focused on using the existing on-orbit spacecraft to achieve greater residual value,or applying on-orbit spacecraft to emergency response missions.This thesis focuses on the fast response to Earth observation missions.Through the adjustment of the ground-track of the on-orbit spacecraft,the emergency observation task for the specified ground target point is completed.According to the different maneuvering modes of the spacecraft,it can be divided into two aspects:for impulse maneuver,this paper mainly studies the reachable domain of the ground-track under the impulse magnitude constraint,and the time-optimal ground-track problem is analytically solved.For the low-thrust orbit maneuver,combined with the current popular shape-based method,the fuel consumption and response time are used as the optimization indicators,and the ground-track adjustment problem is solved by two-and three-dimensional shape functions respectively.The specific research contents of this paper are as follows:For the reachable domain problem of the ground-track,considering the influence of J₂ perturbation and the impulse magnitude constraint,the initial reachable domain problem is transformed into solving the reachable range of the longitude difference at the same latitude.According to the relationship between the orbital parameters and the latitude and longitude,the range of variation of the longitude difference can be obtained by solving the time difference between the maneuvering orbit and the initial reference orbit.Finally,according to the different coplanar impulse constraints,the golden section search method and the Newton iteration method are used to solve the reachability domain of the ground-track.For the single impulse time-optimal ground-track adjustment problem under the fuel constraint,the approximate analytical solution of the optimal maneuver position of the impulse is obtained by the time equation.Further,under the constraint of the impulse magnitude,the relationship between the impulse component and the change of the orbital parameter is approximated based on the Gauss's variational equations.By equaling the time equations obtained by the latitude and longitude of the target site respectively,the analytical expression of the impulse vector is finally obtained.For the low-thrust fuel-optimal ground-track adjustment problem,the polar coordinate system is established based on the initial orbital plane,and the original Fourier series fitting method is improved to avoid the equality constraint of the dynamic equation in the optimization process,so that it can be applied to the multiple-revolution transfer ground-track adjustment problem.For the case where the final orbital shape is free and fixed,the optimization is solved separately.For the low-thrust time-optimal ground-track adjustment problem,the cylindrical coordinate system is established based on the initial orbital plane.The out-of-plane position component is expressed as a function of the change of the orbital inclination and the right ascension of ascending node,which will make the transfer trajectory always between the initial orbital plane and the final orbital plane.Through the new boundary condition constraints,the multi-circle time optimal ground-track adjustment problem is solved.