Visual inspection of space-borne assets is of increasing interest to spacecraft operators looking to plan maintenance, characterise damage, and extend the life of high-value satellites in orbit. The environment of Low Earth Orbit (LEO) presents unique challenges when planning inspection operations to maximise visibility, information, and data quality. Specular reflection of sunlight from spacecraft bodies, self-shadowing, and dynamic lighting in LEO significantly impact the quality of data captured throughout an orbit. This is exacerbated by the relative motion between spacecraft, which introduces variable imaging distances and attitudes during inspection. Planning inspection trajectories with the aide of simulation is a common approach. However, the ability to design and optimise an inspection trajectory specifically to improve the resulting image quality as a function of the scene remains largely unexplored. In this work, we present partial derivative LITE, an end-to-end differentiable simulation pipeline for on-orbit inspection operations. We leverage state-of-the-art differentiable rendering tools and a custom orbit propagator to enable end-to-end optimisation of orbital parameters based on visual costs. partial derivative LITE enables us to automatically design non-trivial trajectories, vastly improving the quality and usefulness of attained data. To our knowledge, our lighting-informed differentiable inspection-planning pipeline is the first of its kind and provides new insights into modern computational approaches to spacecraft mission planning.
The rise in the deployment of low Earth orbit satellite constellations has reshaped the space utilization landscape, driving unprecedented demand for multi-satellite launches. This trend arises from the growing need for low-latency global connectivity, high resolution observation and more accurate navigation services. In this context, this article provides a critical review of current and emerging strategies for large-scale deployment of satellites, with a particular focus on their implications for spacecraft configuration and structural design. The review analyzes the evolution of launch strategies, from the first low orbit multi-satellite projects to recent and future mega-constellation initiatives. The analysis includes not only the launch vehicles but also the stacking techniques, the ancillary structures for multi-satellite deployment and the attachment and separation mechanisms that make them possible. Furthermore, the most popular deployment strategies are compared, relating the different techniques to the design decisions that ensure the integrity of the satellite during launch and orbital release. Then, launcher efficiency and suitability for low-cost and massive orbital injections are evaluated. Results show that flat-panel satellites achieve the lowest commercial cost per kilogram of payload, particularly when using stacking configurations. Thus, a reduction of approximately 66% with respect to dispenser-ring integration strategies and about 29% lower than rideshare commercial prices, underscoring the advantages of dedicated missions based on satellite stacking. Meanwhile, emerging integration strategies are expected to significantly reduce those figures in the coming years by adopting larger and more efficient launch configurations. This review provides a solid basis for optimizing the deployment of large-scale satellite constellations, fully aligned with the requirements of modern space mission demands.
Motor performance depends on muscle activation, a relationship established under Earth gravity. However, how altered gravity — such as microgravity or hypergravity — affects the link between muscle activity and motor learning remains unclear. This is especially relevant for astronauts, who rely heavily on manual tasks. This study examined the relationship between upper-limb muscle activity and motor learning under gravity compensation (GC) and augmented-gravitational load (AG) using an active exoskeleton. Motor learning was defined as an improvement in fine motor performance. Seven participants were tested under GC and seven under AG during repeated aiming movements across 16 sessions. Under GC, performance improved significantly. A positive relation between motor learning and EMG was identified in some sessions under GC. Under AG, no learning effect or relations with EMG can be seen. We suggest that gravity compensation may be less familiar than working with heavy loads, requiring greater muscular control under GC. Importantly, participants had no prior experience with altered gravity, enabling us to observe natural sensory-motor adaptation. The results identified sensorimotor adaptation during movement under gravity compensation. This suggests that individuals without prior exposure may initially experience reduced movement precision and increased effort. The observed adaptation mechanisms may also be relevant for understanding motor behavior in real altered-gravity environments. The observed sensorimotor adaptation highlights the importance of considering adaptation processes when designing human–machine interfaces and operational procedures for altered-gravity environments. Further research is required to determine the extent to which these findings generalize to real microgravity conditions.
