The methodology of atmospheric-force-based satellite relative motion control has matured significantly over the past decade, with several missions successfully demonstrating differential drag for in-plane formation-flying control, most recently in the Advanced Nanosatellites Systems for Earth observation Research (ANSER) mission of the Spanish Institute of Aerospace Technology (INTA). In ANSER, differential drag was used operationally to alter the in-plane relative motion of a cluster of 3 x 3U CubeSats, featuring a set of deployable flaps that achieves a ratio between the maximum and minimum cross-sectional areas of 21:1. Building on this achievement, a logical next milestone for the mission is the first in-orbit demonstration of differential lift for controlling out-of-plane motion,  especially considering the current slight difference in inclination and RAAN between the three satellites. This is an aerodynamic actuation mode that has not yet been experimentally validated in space but has been theoretically studied at the University of Stuttgart for several years, and now within the Collaborative Research Centre “Advancing Technologies of Very Low Altitude Satellites (ATLAS)” established in 2024. Before such a maneuver can be performed in orbit, a comprehensive preparatory study is required to define a robust and meaningful demonstration strategy.
This paper presents the analysis, design methodology, and expected performance of the planned differential-lift demonstration maneuver, prepared collaboratively by the University of Stuttgart’s Institute of Space Systems and INTA. Using a high-fidelity relative-motion simulation framework that incorporates spacecraft attitude profiles, realistic aerodynamic models, and uncertainties in atmospheric density and aerodynamic coefficients, we derive a sequence of attitude commands that produces a measurable out-of-plane separation by commanding lift asymmetries between the satellites. Several maneuver strategies are evaluated considering geometric observability, sensitivity to environmental disturbances, operational constraints, and safety requirements for cluster integrity. The resulting maneuver concept maximizes the expected differential-lift signal while remaining compatible with the existing ANSER's longitudinal formation flying and ground-operations workflow.
The presented analysis forms the foundation for the upcoming in-orbit execution of the maneuver by INTA, representing a decisive step toward demonstrating full three-dimensional relative-orbit control without propulsion on CubeSat platforms. This work contributes to a key enabling technology for future fractionated and distributed Earth-observation missions relying solely on aerodynamic actuation.