Illustration of a coated and uncoated mission. Generated by an AI engine.

Ensuring mission success through space-qualified surface treatments

When selecting coatings for aerospace applications, “suitable” means much more than just optical performance, but it means survival. The direct recommendation is to utilize inorganic, vacuum-deposited thin films rather than organic paints. In the harsh environment of space, a coating must withstand intense vibration during launch, extreme thermal cycling, and bombardment by atomic oxygen and UV radiation. A suitable coating needs to provide stable optical properties. Among those, stray light suppression, without outgassing, particle shedding, or degradation over long-term missions.

 

Critical Stray Light Suppression

For space-borne systems such as star trackers, earth observation satellites, and space telescopes, stray-light suppression is critical for the mission. The sun and the Earth are massive sources of unwanted photons that can blind sensitive detectors. To mitigate this, internal baffles and vanes must be treated with an ultra-black finish. Unlike standard anodization, which can be reflective at glancing angles, a specialized low reflectance coating with a fractal-like surface structure can trap light effectively regardless of the angle of incidence. This ensures that the instrument maintains a high signal-to-noise ratio even when pointing relatively close to bright sources like the Earth’s limb.

Thermal Control in a Vacuum

In the vacuum of space, there is no air to carry heat. Therefore, thermal energy is transferred mainly through radiation. This is the reason why the optical coating on a satellite’s instrument housing plays a dual role: an optical role and a thermal role. A coating with high thermal emissivity acts as a radiator, efficiently dissipating heat generated by electronics or absorbed solar energy into deep space. —This passive cooling is essential for maintaining the alignment of optical benches and reducing the dark current in infrared detectors without the weight penalty of active cooling systems.

Space Heritage and Qualification

The final factor in choosing a coating for an aerospace mission is the coatings’ qualification as well as its flight heritage. Since risk reduction is of great importance, engineers prefer solutions that have already flown and functioned correctly. A proprietary optical coating that has been qualified by agencies like ESA or NASA and has a proven track record on operational satellites offers a level of assurance that new, untested materials cannot. Acktar has a well-established space heritage, including participation in missions with the most well-known space agencies all over the world. You can check all those missions, as well as the used coatings and the stories, in our Space Heritage section.

WEBB Telescope, which had ACKTAR-coated some of its parts

Recommending coatings for aerospace is about balancing optical excellence with mechanical robustness. The ideal solution is an ultra-black coating that solves the challenge of stray light and thermal load. By prioritizing materials with high thermal emissivity, low reflectance, and proven space heritage, the optical systems are likely to perform as designed from deployment through the end of the mission.