A continuous-time formulation for optimal task scheduling and quality-of-service assurance in nanosatellites

Satellite scheduling concerns an operations research problem that aims at planning the execution of a given set of tasks, either in real-time onboard the spacecraft or offline in the ground station. In particular, the task scheduling problem for nanosatellites has been the focus of recent research, given the unique set of constraints and applications, and considering their limited power resources. This paper applies the continuous-time methodology to deliver a novel scheduling formulation for the nanosatellite scheduling problem with increased flexibility and versatility to the decision-maker. Here, we adopt the concept of priority slots and follow the Multi-Operation Sequencing with Synchronized Start Times (MOS-SST) representation to yield a Mixed-Integer Linear Programming (MILP) formulation that considers constraints on time synchronization, mission quality-of-service, and management of shared resources. By comparing our continuous-time strategy with existing discrete-time alternatives, we showed that the proposed method can solve representative problem instances in a considerably shorter time, while being able to deal with real-valued constraint functions.