Stray light solution for Ghgsat nanosatellite

GHGSat is world’s first nanosatellite dedicated for monitoring greenhouse gas (GHG) and air quality gas (AQG) emissions from any industrial site in the world. The satellite was designed and constructed by MPB Communications to monitor carbon dioxide (CO2) and methane (CH4) from a low earth orbit (about 500 km).

To reach the designated resolution of less than 50 meters and high precision of greenhouse gases monitoring, the nanosatellite has large aperture in order to collect enough optical signal. The aperture of about 10cm causes significant stray light issues with limited solution options without adding too much weight to the light weight satellite.

As the stray light was the main concern in this project, many precautions was taken. As a solution for blocking unwanted light, baffle with many vanes was used. However, having the vanes is not optimal solution without high absorbing coating applied on it. The coating requirements was low reflectance, no outgassing in space environment and long life stability, being a satellite inaccessible for maintenance.

The chosen coating for stray light elimination was Acktar Vacuum Black^TM. Hemispherical reflectance and BRDF data was examined before making the choice.

The satellite was launched in June 2016 and the images was analyzed to ensure the aimed resolution and precision of the optical system. After almost two years of activity, no visible changes was discovered in image quality nor stray light issues detected.