Nowadays, the proliferation of small satellites brings the skyrocketing rise in space data, especially the shift to on-orbit computing needs. On one hand, with the increasing volume of data generation, like high-resolution remote sensing images, on-orbit computing produces near real-time onboard solutions and quick responses. However, constrained by the limited size and energy supply of satellites, achieving energy-efficient on-orbit computing remains a crucial challenge. In this article, an on-orbit remote sensing image processing complex task scheduling model facing a heterogeneous multiprocessor system (HMPS) is pro-posed. First, aiming at accelerating image processing, we establish a novel parallel task execution model using a directed acyclic graph (DAG) to universally describe typical missions, i.e., cloud detection, geometric correction, and image classification. Subsequently, a mathematical task scheduling formulation is defined to calculate the makes pan, and total energy consumption (TEC)required when executing DAG on HMPS. Second, a new Pareto-based iterated greedy optimizer (PIGO) is devised to complete the energy- and time-efficient task execution and resource allocation on HMPS through confined inserting mutation, destruction-reconstruction, and local search. Finally, we build an emulatedon-orbit HMPS to conduct experiments. The results show that, in comparison with the scheme without model scheduling, the cost savings of around 51% and 54% in make span and TEC, respectively, are achieved by the proposed model. More over, the HMPS configured with our methodology can obtain 2.2ximprovement in energy efficiency and process up to 2.56x105pixels per unit of power (W) and time (s)