Optimal Strip Attitude Command of Earth Observation Satellite using Differential Dynamic Programming

TL;DR

This paper develops an optimal control method using differential dynamic programming to improve the scan profile of Earth observation satellites with TDI cameras, minimizing angular velocity to enhance image quality.

Contribution

It introduces a novel optimal control formulation leveraging the additional DOF of modern agile EOS with TDI cameras, solved efficiently via DDP.

Findings

Achieves near-optimal scan profiles efficiently.

Reduces angular velocity to improve image quality.

Validated through simulations and comparisons.

Abstract

This paper addresses the optimal scan profile problem for strip imaging in an Earth observation satellite (EOS) equipped with a time-delay integration (TDI) camera. Modern TDI cameras can control image integration frequency during imaging operation, adding an additional degree of freedom (DOF) to the imaging operation. On the other hand, modern agile EOS is capable of imaging non-parallel ground targets, which require a substantial amount of angular velocity and angular acceleration during operation. We leverage this DOF to minimize various factors impacting image quality, such as angular velocity. Initially, we derive analytic expressions for angular velocity based on kinematic equations. These expressions are then used to formulate a constrained optimal control problem (OCP), which we solve using differential dynamic programming (DDP). We validate our approach through testing and comparison with reference methods across various practical scenarios. Simulation results demonstrate that our proposed method efficiently achieves near-optimal solutions without encountering non-convergence issues.