The increasing urgency of climate change mitigation necessitates innovative solutions beyond terrestrial efforts. Space-based solar geoengineering – particularly a Planetary Sunshade System (PSS) positioned near the photo-gravitational equilibrium point L<inf>1</inf>^∗, which lies closer to the Sun than the classical L<inf>1</inf> due to the effect of solar radiation pressure – has been proposed as a potential method to reduce incoming solar radiation and stabilize global temperatures. This paper presents the preliminary design of a precursor mission aimed at demonstrating key technologies essential for the deployment of a full-scale PSS. The proposed mission features a 12U CubeSat equipped with a 400 [m²] solar sail, which will be used for propulsion, attitude control, and station-keeping at L<inf>1</inf>^∗. The mission objectives focus on validating the long-term performance of optical shielding materials, demonstrating solar sailing as a sustainable propulsion method, and assessing the feasibility of autonomous orbit and attitude control systems. The technical and economic feasibility of the precursor mission, with an estimated budget of 10M USD is examined. By addressing key uncertainties in spacecraft formation flying, material degradation, and long-term solar sailing operations, this mission represents a crucial step toward the realization of a scalable PSS for climate intervention.

The objective of this paper is to present a roadmap for the technology development toward a Planetary Sunshade System, a space-based solar geoengineering project aimed at reversible solar radiation modification to mitigate global warming. Earth's climate change is mostly due to the increasing concentration of greenhouse gases in the atmosphere, which leads to a general rise of the temperatures. A space-based geoengineering infrastructure has been previously proposed to reduce the oncoming solar irradiance, by placing a 'solar light umbrella', called Planetary Sunshade System, between the Sun and the Earth. To address the full development of a Planetary Sunshade System, a technology roadmap is needed which considers a step-by-step high-level plan of technology development, mission planning, launch preparation, international cooperation, highlighting the multi-phase development strategy from initial design to final deployment. First, the roadmap phases for production and deployment are outlined in chronological order. The analysis of technology development begins with the current technology readiness level, encompassing system design and factors such as mass, dimensions, area, and the total number of solar-sail satellites. Logistic aspects, including in-space assembly of the fully deployed system, are also examined. Finally, launch preparation is discussed encompassing heavy launcher design, facilities, production and launch sites. The proposed roadmap not only provides a starting point for the design and development of the Planetary Sunshade System but also a critical tool for evaluating the feasibility of direct climate action from space. Through this paper, we aim to establish the groundwork for a future Planetary Sunshade endeavour, and to contribute to the broader discussion on space-based climate action.

The objective of this paper is to present the design of a precursor mission for the Planetary Sunshade System, positioned near the photo-gravitational equilibrium point L1*, located between the Sun and the Earth-Moon system's center of mass. This study pioneers the integrated system engineering design and mission scenario definition. Earth's climate change, driven predominantly by the escalation of greenhouse gases in the atmosphere, poses an unprecedented threat to global stability and sustainability, manifesting through increased global temperatures. In response, a space-based geoengineering infrastructure has been previously proposed as a mitigation measure. It would enable to reduce the oncoming solar irradiance, by placing a 'solar-light umbrella', called Planetary Sunshade, strategically positioned between the Sun and the Earth. The proposed Planetary Sunshade precursor mission aims at pushing forward through in-space testing some of the critical enabling technologies for such a space-based climate change mitigation solution. First, the precursor Planetary Sunshade System and mission requirements are discussed, for the first time to the best knowledge of the authors. Emphasis is put on the astrodynamics of the mission, analyzing the orbital regimes suitable for maximizing efficacy and stability. Then, the system design is introduced, based on small satellite components, focusing on critical aspects of subsystems such as solar sail, attitude and orbit control system, deployable structures and mechanisms, thermal system, and telemetry. Particular attention will be paid to the choice of solar sail materials, emphasizing their optical properties. This precursor mission is meant to serve not only as a proof of concept but also as a critical technology testbed. By studying the feasibility of such a mission, we contribute to a broader discussion on possible space-based interventions for climate change mitigation. Our work aligns with several UN Sustainable Development Goals, notably SDG 13 (Climate Action), by exploring innovative solutions to mitigate climate change, and SDG 9 (Industry, Innovation, and Infrastructure), by pushing the boundaries of current space technology.