With growing concern over climate change, measurements performed by meteorological satellites, such as the MTG (Meteosat Third Generation) are becoming increasingly necessary. Earth Observation (EO) satellites such as those commissioned by the European Union (Copernicus sentinel missions) for agricultural monitoring, tracking wildfires, and monitoring sea levels carry increasingly complex remote sensing optical instrumentation. These systems require thermo-optical coatings to minimise the stray light entering the instrument, which would otherwise degrade performance. Additionally, next generation communication satellites are incorporating higher power density payloads, which makes regulation of the internal temperatures of satellites more challenging while large volume 'satellite constellations' can impact on scientific observations. These challenges can be met by the development of a robust 'space complaint' thermo-optical coating with high solar absorptance and high thermal emittance.
Conclusions
- A Design of Experiments revealed main influencing parameters which were used in the following development and optimisation of sol-gel formulations.
- A baseline sol-gel prototype was produced based on optimized formulation preparation parameters. The thermo-optical properties, heat resistance, adhesion and outgassing of the baseline coating formulation were analysed, showing good results.
- The curing cycle was optimised.
- An inorganic sol-gel coating formulation based on tetraethyl orthosilicate was developed. The formulation preparation parameters were optimized, and the most relevant properties of the coating were investigated.
- Alternative black pigments were tested, and it was shown that a bone char pigment shows the best thermo-optical characteristics.
- Basic initial dip-coating experiments allowed to estimate the coating application parameters.
- The development of alternative hybrid organic-inorganic sol-gel formulations was initiated, which included optimisation of components ratio and testing of additional cross-linking agent. Two, the most promising formulations, based on epoxy silane and methacrylic silane, were investigated and the thermo-optical properties were measured. These formulations have shown the best results to date and are recommended for the next stages of this project.
- Several representative hardware parts were coated by dip-coating using “5_G” formulation with Cosmic Black pigment. In general, the positive results were achieved but the dip-coating process requires some adjustments to provide more consistent coating thickness.
