Mission-critical system, such as satellite systems, healthcare systems, and nuclear power plant control systems, undergo rigorous testing to ensure they meet specific operational requirements throughout their operation. This includes Operational Acceptance Testing (OAT), which aims to ensure that the system functions correctly under real-world operational conditions. In satellite development, In-Orbit Testing (IOT) is a crucial OAT activity performed regularly and as needed after deployment in orbit to check the satellite's performance and ensure that operational requirements are met. The scheduling of an IOT campaign, which executes multiple IOT procedures, is an important yet challenging problem, as it accounts for various factors, including satellite visibility, antenna usage costs, testing time periods, and operational constraints. To address the IOT scheduling problem, we propose a multi-objective approach to generate near-optimal IOT schedules, accounting for operational costs, fragmentation (i.e., the splitting of tests), and resource efficiency, which align with practitioners' objectives for IOT scheduling. Our industrial case study with SES Techcom shows significant improvements, as follows: an average improvement of 49.4% in the cost objective, 60.4% in the fragmentation objective, and 30% in the resource usage objective, compared to our baselines. Additionally, our approach improves cost efficiency by 538% and resource usage efficiency by 39.42% compared to manually constructed schedules provided by practitioners, while requiring only 12.5% of the time needed for manual IOT scheduling.